Uniform Mechanical Code- 2009 Chapter 5

CHAPTER 5EXHAUST SYSTEMS

501.0 Scope.This chapter includes requirements for environ-mental air ducts, product-conveying systems, andcommercial hoods and kitchen ventilation.

Part I – Environmental Air Ducts and Product-Conveying Systems.

502.0 Definitions.For the purposes of this chapter, the following defi-nitions apply:ACCESS PANEL – A closure device used to coveran opening into a duct, an enclosure, equipment, oran appurtenance. [NFPA 96:3.3.1]AIR INTAKES – An opening in a building's envelopewhose purpose is to allow outside air to be drawninto the structure to replace inside air that isremoved by exhaust systems or to improve thequality of the inside air by providing a source of airhaving a lower concentration of odors, suspendedparticles, or heating content. [NFPA 96:3.3.2]AIR POLLUTION CONTROL DEVICES – Equip-ment and devices used for the purpose of cleaningair passing through them or by them in such amanner as to reduce or remove the impuritiescontained therein. [NFPA 96:3.3.3]APPURTENANCE – An accessory or a subordinatepart that enables the primary device to perform orimprove its intended function. [NFPA 96:3.3.5]BAFFLE PLATE – An object placed in or near anappliance to change the direction or retard the flow ofair, air-fuel mixtures, or flue gases. [NFPA 96:3.3.7]CERTIFIED PERSON – A person trained and certi-fied by the equipment manufacturer, or by a recog-nized organization through a formal certificationprogram for the system to be serviced or cleaned,that is acceptable to the Authority Having Jurisdic-tion.CLASSIFIED – See Listed.CLEAN(ING) – For kitchen exhaust systems andcooking equipment, the act of removing grease, oildeposits, and other residue. [NFPA 96:3.3.11]CLEARLY IDENTIFIED – Capable of being recog-nized by a person of normal vision without causinguncertainty and indecisiveness about the location oroperating process of the identified item. [NFPA96:3.3.12]

CLOSED COMBUSTIBLE CONSTRUCTION –Combustible building construction, including walls,structural framing, roofs, roof ceilings, floors, andfloor-ceiling assemblies continuously enclosing agrease duct on four sides where one or more sidesrequire protection per Section 507.2. [NFPA96:3.3.13.1]COMBUSTIBLE MATERIAL – Material subject to anincrease in combustibility or flame-spread ratingbeyond the limits established in the definition ofLimited-Combustible Material.COMMERCIAL FOOD HEAT-PROCESSINGEQUIPMENT – Equipment used in a food establish-ment for heat-processing food or utensils and thatproduces grease vapors, steam, fumes, smoke, orodors that are required to be removed through alocal exhaust ventilation system.COMPENSATING HOOD – A hood that has anoutside-air supply with air delivered below orwithin the hood. When makeup air is diffuseddirectly into the exhaust within the hood cavity, itbecomes a short-circuit hood.CONCEALED SPACES – That portion(s) of abuilding behind walls, over suspended ceilings, inpipe chases, attics, and elsewhere whose size mightnormally range from 1-3/4 inch (44.45 mm) studspaces to eight (8) foot (2.44 m) interstitial trussspaces and that might contain combustible materialssuch as building structural members, thermaland/or electrical insulation, and ducting. Suchspaces have sometimes been used as HVAC plenumchambers. [NFPA 96:3.3.45.1]CONTINUOUS ENCLOSURE – A recognized archi-tectural or mechanical component of a buildinghaving a fire resistance rating as required for thestructure and whose purpose is to enclose the vaporremoval duct for its full length to its terminationpoint outside the structure without any portion ofthe enclosure having a fire resistance rating less thanthe required value. [NFPA 96:3.3.22.1]CONTINUOUS WELD – A metal-joining method thatproduces a product without visible interruption orvariation in quality. For the purpose of the defini-tion, it specifically includes the exhaust compartmentof hoods and welded joints of exhaust ducts, yetspecifically does not include filter support frames orappendages inside hoods. [NFPA 96:3.3.14]COOKING APPLIANCE FLUE OUTLET – Theopening or openings in a cooking device where

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vapors, combustion gases, or both leave the cookingdevice. There might or might not be ductworkattached to this opening.DAMPER – A valve or plate within a duct or itsterminal components for controlling draft or the flowof gases, including air. [NFPA 96:3.3.15]DETECTION DEVICES – Electrical, pneumatic,thermal, mechanical, or optical sensing instruments,or subcomponents of such instruments, whosepurpose is to cause an automatic action upon theoccurrence of some preselected event. In the contextof this document, the event in question could beexcessive temperature or flame, and the action couldbe the operation of a fire-extinguishing system.DIPS – Depression or cup like places in horizontalduct runs in which liquids could accumulate. [NFPA96:3.3.17]DISCHARGE – The final portion of a duct or pipewhere the product being conveyed is emptied orreleased from confinement; the termination point ofthe pipe or duct. [NFPA 96:3.3.18]EASILY ACCESSIBLE – See Accessible, Readily inSection 203.0, Chapter 2.ENVIRONMENTAL AIR DUCT – Ducting used forconveying air at temperatures not exceeding 250˚F(121˚C) to or from occupied areas of any occupancythrough other than heating or air-conditioningsystems, such as ventilation for human usage,domestic kitchen range exhaust, bathroom exhaustducts, and domestic-type clothes dryer exhaust ducts.FACTORY-BUILT GREASE ENCLOSURES – Alisted factory-built grease duct enclosure systemevaluated for reduced clearances to combustibles,and as an alternative to a duct with its fire-ratedenclosure. [NFPA 96:3.3.22.2.1]FIELD-APPLIED GREASE DUCT ENCLOSURES –A listed system evaluated for reduced clearances tocombustibles, and as an alternative to a duct with itsfire-rated enclosure. [NFPA 96:3.3.22.2.2]FLAMMABLE VAPOR OR FUMES – The concentra-tion of flammable constituents in air that exceedstwenty-five percent (25%) of its Lower FlammabilityLimit (LFL).FIRE BARRIER WALL – A wall assemblycomplying with the requirements of NFPA 221, Stan-dard for Fire Walls and Fire Barrier Walls, having a fireresistance rating of four (4) hours.FIRE PARTITION – An interior wall or partition of abuilding that separates two areas and serves torestrict the spread of fire but does not qualify as afire wall.FIRE RESISTANCE RATING – A relative value inminutes or hours assigned to materials or assembliesthat have withstood a fire exposure as established in

accordance with NFPA 251, Standard Methods of Testsof Fire Endurance of Building Construction andMaterials.FUME INCINERATORS – Devices utilizing intenseheat or fire to break down and/or oxidize vaporsand odors contained in gases or air being exhaustedinto the atmosphere. [NFPA 96:3.3.27]FUSIBLE LINK – A form of fixed-temperature heat-detecting device sometimes employed to restrain theoperation of an electrical or mechanical control untilits designed temperature is reached. Such devices areto be replaced following each operation.GREASE – Rendered animal fat, vegetable short-ening, and other such oily matter used for thepurposes of and resulting from cooking and/orpreparing foods. Grease might be liberated andentrained with exhaust air or might be visible as aliquid or solid.GREASE DUCTS – A containment system for thetransportation of air and grease vapors that isdesigned and installed to reduce the possibility ofthe accumulation of combustible condensation andthe occurrence of damage if a fire occurs within thesystem. [NFPA 96:3.3.20.2]GREASE FILTER – A removable component of thegrease removal system designed to capture greaseand direct it to a safe collection point before it entersa duct system. Filters are expected to minimize theprojection of flames downstream when attacked byflame on the upstream side and are expected tomaintain their strength, shape, and integrity whenexposed to the anticipated rough handling, cleaning,and service found in the field.GREASE FILTER, MESH–TYPE – A general-purpose air filter designed to collect and retain lintand grease from the air passing through it. This typeof filter is not tested, listed, or acceptable forcommercial cooking operations due to the increasedfire hazard.GREASE REMOVAL DEVICES – A system ofcomponents designed for and intended to processvapors, gases, and/or air as it is drawn through suchdevices by collecting the airborne grease particlesand concentrating them for further action at somefuture time, leaving the exiting air with a loweramount of combustible matter. [NFPA 96:3.3.30]GREASE-TIGHT – Constructed and performing insuch a manner as not to permit the passage of anygrease under normal cooking conditions. [NFPA96:3.3.31]HIGH BROILER – See Upright Broiler.[NFPA96:3.3.8.1]HIGH LIMIT CONTROL – An operating deviceinstalled in and serving as an integral component ofa deep-fat fryer. Its purpose is the secondary limita-

UNIFORM MECHANICAL CODE

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502.0

tion of temperature allowed by the cooking opera-tion and, if that temperature is exceeded, the auto-matic interruption of the thermal energy input.[NFPA 96:3.3.32]HOOD – An air-intake device connected to amechanical exhaust system for collecting andremoving grease, vapors, fumes, smoke, steam, heat,or odors from commercial food heat-processingequipment.

Fixed Baffle – A listed unitary exhaust hooddesign where the grease removal device is anonremovable assembly that contains an inte-gral fire-activated water-wash fire-extinguishingsystem listed for this purpose. [NFPA96:3.3.33.1]Type I – is a kitchen hood for collecting andremoving grease and smoke.Type II – is a general kitchen hood for collectingand removing steam, vapor, heat, or odors.

INTERCONNECTED – Mutually assembled toanother component in such a manner that the opera-tion of one directly affects the other or that thecontents of one specific duct system are allowed toencounter or contact the products being moved byanother duct system. [NFPA 96:3.3.34]LIMITED-COMBUSTIBLE MATERIAL – A buildingconstruction material that does not comply with thedefinition of noncombustible material, that, in theform in which it is used, has a potential heat valuenot exceeding 3,500 Btu/lb. (8141 kJ/kg) (see NFPA259, Standard Test Method for Potential Heat of BuildingMaterials), and that complies with either of thefollowing (A) or (B). Materials subject to an increasein combustibility or flame-spread rating beyond thelimits herein established through the effects of age,moisture, or other atmospheric conditions shall beconsidered combustible.(A) Materials having a structural base of noncom-

bustible material, with a surfacing not exceedinga thickness of 1/8 inch (3.2 mm), and with aflame-spread rating not greater than fifty (50).

(B) Materials in the form and thickness used, otherthan as described in (A), having neither a flame-spread rating greater than twenty-five (25) norevidence of continued progressive combustionand of such composition that surfaces thatwould be exposed by cutting through the mate-rial on any plane would have neither a flame-spread rating greater than twenty-five (25) norevidence of continued progressive combustion.

LIQUID-TIGHT – Constructed and performing insuch a manner as not to permit the passage of anyliquid at any temperature. [NFPA 96:3.3.35]NONCOMBUSTIBLE MATERIAL – A material that,in the form in which it is used and under the condi-

tions anticipated, will not ignite, burn, supportcombustion, or release flammable vapors whensubjected to fire or heat. Materials that are reportedas passing ASTM E 136, Standard Test Method forBehavior of Materials in a Vertical Tube Furnace at750°C, shall be considered noncombustible materials.[NFPA 220:3.3.4]OPEN COMBUSTIBLE CONSTRUCTION –Combustible building constructions including wall,structural framing, roof, roof ceiling, floor, and floorceiling assemblies adjacent to a grease duct on threeor fewer sides where one or more sides requireprotection per Section 507.2. [NFPA 96:3.3.13.2]PITCHED – To be fixed or set at a desired angle orinclination. [NFPA 96:3.3.37]PRODUCT-CONVEYING DUCT – Ducting used forconveying solid particulates, such as refuse, dust,fumes, and smoke; liquid particulate matter, such asspray residue, mists, and fogs; vapors, such asvapors from flammable or corrosive liquids; noxiousand toxic gases; and air at temperatures exceeding250ºF (121ºC).RECIRCULATING SYSTEMS – Systems for controlof smoke or grease-laden vapors from commercialcooking equipment that do not exhaust to theoutside. [NFPA 96:3.3.39]REMOVABLE – Capable of being transferred toanother location with a limited application of effortand tools. [NFPA 96:3.3.40]REPLACEMENT AIR – See Air, Makeup in Section203.0, Chapter 2.SALAMANDER BROILER – See Upright Broiler.[NFPA 96:3.3.8.2]SECONDARY FILTRATION – Fume incinerators,thermal recovery units, air pollution control devicesor other filtration media installed in ducts or hoodslocated in the path of travel of exhaust products afterthe initial filtration.SHALL – Indicates a mandatory requirement.SINGLE HAZARD AREA – As considered in theapplicable extinguishing system standard (seeSection 513.2) or as determined by the AuthorityHaving Jurisdiction.SOLID COOKING FUEL – Any solid, organic,consumable fuel such as briquette, mesquite, hard-wood, or charcoal. [NFPA 96:3.3.43]SOLID-FUEL COOKING EQUIPMENT – Cookingequipment that is fired with solid cooking fuel. Thisequipment includes ovens, tandoori charcoal pots,grills, broilers, rotisseries, barbecue pits, or any othertype of cooking equipment that derives all or part ofits heat source from the burning of solid cooking fuel.

EXHAUST SYSTEMS 502.0

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SOLVENT – A substance (usually liquid) capable ofdissolving or dispersing another substance; a chem-ical compound designed and used to convert solidi-fied grease into a liquid or semi-liquid state in orderto facilitate a cleaning operation. [NFPA 96:3.3.44]SPARK ARRESTER – A device or method thatminimizes the passage of airborne sparks andembers into a plenum, duct, and flue. [NFPA96:3.3.46]TERMINATION – The final or intended end portionof a duct system that is designed and functions tofulfill the obligations of the system in a satisfactorymanner.THERMAL RECOVERY UNIT – A device or series ofdevices whose purpose is to reclaim only the heatcontent of air, vapors, gases, or fluids that are beingexpelled through the exhaust system and to transferthe thermal energy so reclaimed to a locationwhereby a useful purpose can be served. [NFPA96:3.3.47]TRAP – A cup like or U-shaped configurationlocated on the inside of a duct system componentwhere liquids can accumulate. [NFPA 96:3.3.49]UPRIGHT BROILER – An appliance used in thepreparation of food whereby foods are exposed tointense radiant heat, and perhaps to convective heat,with the food and the radiant source not limited to ahorizontal mode. [NFPA 96:3.3.8.3]502.1 Product-Conveying Ducts – Classification.Product-conveying ducts shall be classifiedaccording to their use, as follows:

Class 1. Ducts conveying nonabrasives, such assmoke, spray, mists, fogs, noncorrosivefumes and gases, light fine dusts, orpowders.

Class 2. Ducts conveying moderately abrasiveparticulate in light concentrations, suchas sawdust and grain dust, and buffingand polishing dust.

Class 3. Ducts conveying Class 2 materials inhigh concentrations and highly abrasivematerials in low concentrations, such asmanganese, steel chips, and coke.

Class 4. Ducts conveying highly abrasive mate-rial in high concentrations.

Class 5. Ducts conveying corrosives, such asacid vapors.

503.0 Motors, Fans, and Filters.503.1 General. Motors and fans shall be sized toprovide the required air movement. Motors in areasthat contain flammable vapors or dusts shall be of atype approved for such environments. A manually

operated remote control installed at an approvedlocation shall be provided to shut off fans or blowersin flammable vapor or dust systems. Electrical equip-ment used in operations that generate explosive orflammable vapors, fumes, or dusts shall be inter-locked with the ventilation system so that the equip-ment cannot be operated unless the ventilation fansare in operation. Motors for fans used to conveyflammable vapors or dusts shall be located outsidethe duct or shall be protected with approved shieldsand dustproofing. Motors and fans shall be acces-sible for servicing and maintenance.503.2 Fans. Parts of fans in contact with explosive orflammable vapors, fumes, or dusts shall be of nonfer-rous or nonsparking materials or their casing shall belined or constructed of such material. When the sizeand hardness of materials passing through a fancould produce a spark, both the fan and the casingshall be of nonsparking materials. When fans arerequired to be spark-resistant, their bearings shallnot be within the airstream, and all parts of the fanshall be grounded. Fans in systems handling mate-rials that are likely to clog the blades, and fans inbuffing or woodworking exhaust systems, shall be ofthe radial-blade or tube-axial type.

Equipment used to exhaust explosive orflammable vapors, fumes, or dusts shall bear anidentification plate stating the ventilation rate forwhich the system was designed.

Fans located in systems conveying corrosivesshall be of materials that are resistant to the corrosiveor shall be coated with corrosion-resistant materials.503.3 Air filters shall be listed units. Liquid adhesivecoatings used on filters shall have a flash point of350˚F (177˚C) or higher, as determined by the FireCode standards.

504.0 Environmental Air Ducts.504.1 Makeup and Exhaust-Air Ducts. Environ-mental air ducts not regulated by other provisions ofthis code shall comply with this section. Ducts shallbe substantially airtight and shall comply with theprovisions of Chapter 6. Exhaust ducts under posi-tive pressure shall not extend into or through ductsor plenums. Exhaust ducts shall terminate outsidethe building and shall be equipped with back-draftdampers. Environmental air ducts that have an alter-nate function as a part of an approved smoke-controlsystem do not require design as Class 1product-conveying ducts.504.2 Domestic Range Vents. Ducts used fordomestic kitchen range ventilation shall be of metaland shall have smooth interior surfaces. Ducts fordomestic range hoods shall only serve cooking appli-ances.


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502.0 – 504.2

Exception: Ducts for domestic kitchen down-draft grill-range ventilation installed under aconcrete slab floor may be of approved Schedule40 PVC provided:(1) The under-floor trench in which the duct is

installed shall be completely backfilled withsand or gravel.

(2) Not more than one (1) inch (25 mm) of six(6) inch diameter (152 mm) PVC couplingmay protrude above the concrete floorsurface.

(3) PVC pipe joints shall be solvent cemented toprovided an air and grease-tight duct.

(4) The duct shall terminate above gradeoutside the building and shall be equippedwith a back-draft damper.

504.3 Clothes Dryers.504.3.1 Moisture Exhaust Ducts. Moistureexhaust ducts shall terminate on the outside ofthe building and shall be equipped with a back-draft damper. Screens shall not be installed atthe duct termination. Ducts for exhaustingclothes dryers shall not be connected or installedwith sheet metal screws or other fasteners thatwill obstruct the flow. Clothes dryer moistureexhaust ducts shall not be connected to a gasvent connector, gas vent, or chimney, and shallonly serve clothes dryers. Clothes dryer mois-ture exhaust ducts under positive pressure shallnot extend into or through ducts or plenums.504.3.2 Domestic Clothes Dryers. When acompartment or space for a domestic clothesdryer is provided, a minimum four (4) inchdiameter (102 mm) moisture exhaust duct ofapproved material shall be installed in accor-dance with this section and Section 504.0.

When a closet is designed for the installationof a clothes dryer, a minimum opening of 100square inches (64,516 mm2) for makeup air shallbe provided in the door or by other approvedmeans.

504.3.2.1 Domestic Dryer Vents. Domesticclothes dryer moisture exhaust ducts shallbe of metal and shall have smooth interiorsurfaces.

Exception: Listed clothes dryer transi-tion ducts not more than six (6) feet(1,829 mm) in length may be used inconnection with domestic dryerexhausts.

Flexible clothes dryer transitionducts shall not be concealed withinconstruction.

504.3.2.2 Length Limitation. Unless other-wise permitted or required by the dryermanufacturer’s installation instructions andapproved by the Authority Having Jurisdic-tion, domestic dryer moisture exhaust ductsshall not exceed a total combined horizontaland vertical length of fourteen (14) feet(4,263 mm), including two (2) 90 degree(1.57 rad) elbows. Two (2) feet (610 mm)shall be deducted for each 90 degree (1.57rad) elbow in excess of two.

504.3.3 Commercial Clothes Dryers. Commer-cial dryer exhaust ducts shall be installed inaccordance with their listings. The installation ofcommercial clothes dryer exhaust ducts shallcomply with the appliance manufacturer’sinstallation instructions.

504.4 Heat (Energy) Recovery Ventilators.504.4.1 Heat (energy) recovery ventilators shallbe installed in accordance with their listings andcomply with the appliance manufacturer’sinstallation instructions. Heat (energy) recoveryventilator ducts shall comply with the provi-sions of Chapter 6.

504.5 Termination of Environmental Air Ducts.Environmental air duct exhaust shall terminate aminimum of three (3) feet (914 mm) from propertyline and three (3) feet (914 mm) from openings intothe building.504.6 Gypsum Wallboard Ducts. Bathroom andlaundry room exhaust ducts may be of gypsum wall-board subject to the limitations of Section 602.1.

505.0 Design of Product-Conveying VentilationSystems.505.1 General. A mechanical ventilation or exhaustsystem shall be installed to control, capture, andremove emissions generated from product use orhandling when required by the Building Code orFire Code and when such emissions result in ahazard to life or property. The design of the systemshall be such that the emissions are confined to thearea in which they are generated by air currents,hoods, or enclosures and shall be exhausted by aduct system to a safe location or treated by removingcontaminant's. Ducts conveying explosives orflammable vapors, fumes, or dusts shall extenddirectly to the exterior of the building withoutentering other spaces and shall not extend into orthrough ducts and plenums.

Exception: Ducts conveying vapor or fumeshaving flammable constituents less than 25percent of their Lower Flammability Limit (LFL)may pass through other spaces.

EXHAUST SYSTEMS 504.2 – 505.1

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TABLE 5-1Minimum Conveying Velocities

Note:1 The velocity for aluminum and magnesium powder shall be not less than 4,000 feet per minute (20.3 m/s).

505.1.1 Incompatible materials shall not beconveyed in the same system.505.1.2 In systems conveying flammable vapors,gases, or mists, the concentration shall notexceed 25 percent of the lower flammability limit(LFL).

Exception: Higher concentrations shall bepermitted if the exhaust system is designedand protected in accordance with the Stan-dard on Explosion Prevention Systems inChapter 17, using one or more of thefollowing techniques:(a) Combustible concentration reduction(b) Oxidant concentration reduction(c) Deflagration suppression(d) Deflagration pressure containmentSeparate and distinct systems shall be

provided for incompatible materials.Contaminated air shall not be recirculated to

occupied areas unless contaminant's have beenremoved. Air contaminated with explosive orflammable vapors, fumes, or dusts; flammableor toxic gases; or radioactive material shall notbe recirculated.

505.2 Minimum Velocities and Circulation. Thevelocity and circulation of air in work areas shall besuch that contaminant's are captured by an airstreamat the area where the emissions are generated andconveyed into a product-conveying duct system.Mixtures within work areas where contaminant's aregenerated shall be diluted below twenty-five (25)percent of their lower explosive limit or lowerflammability limit with air that does not containother contaminant's. The velocity of air within theduct shall be not less than set forth in Table 5-1.

Systems for removal of vapors, gases, and smokeshall be designed by the constant velocity or equalfriction methods. Systems conveying particulatematter shall be designed employing the constantvelocity method. Systems conveying explosive orradioactive materials shall be prebalanced throughduct sizing. Other systems may be designed withbalancing devices such as dampers. Dampersprovided to balance airflow shall be provided withsecurely fixed minimum-position blocking devices toprevent restricting flow below the required volumeor velocity.505.3 Makeup Air. Makeup air shall be provided toreplenish air exhausted by the ventilation system.Makeup-air intakes shall be located so as to avoidrecirculation of contaminated air within enclosures.505.4 Hoods and Enclosures. Hoods and enclo-sures shall be used when contaminant's originate in aconcentrated area. The design of the hood or enclo-sure shall be such that air currents created by theexhaust systems will capture the contaminant's andtransport them directly to the exhaust duct. Thevolume of air shall be sufficient to dilute explosive orflammable vapors, fumes, or dusts as set forth inSection 505.2. Hoods of steel shall have a base metalthickness not less than 0.027 inch (0.69 mm) (No. 22gauge) for Class 1 and Class 5 metal duct systems;0.033 inch (0.84 mm) (No. 20 gauge) for hoodsserving a Class 2 duct system; 0.044 inch (1.12 mm)(No. 18 gauge) for hoods serving a Class 3 ductsystem; and 0.068 inch (1.73 mm) (No. 14 gauge) forhoods serving a Class 4 duct system.

Approved nonmetallic hoods and duct systemsmay be used for Class 5 corrosive systems when thecorrosive mixture is nonflammable. Metal hoodsused with Class 5 duct systems shall be protectedwith suitable corrosion-resistant material. Edges of


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505.1 – Table 5-1

Feet perMinute (m/s)Vapors, gases, smoke, fumes AnyFine light dusts, such as cotton, lint, and wood flour (100 meshand under)

2,000 (10.2)

Dry dusts; powders, such as fine rubber molding power, soapdust

2,5001 (12.7)1

Industrial dustsAverage dusts, such as sawdust, grinding dust, coal dustHeavy dusts, such as metal turnings, lead dustsMoist dusts and chips, such as lead dust with chips, sticky buffinglint, quick-lime dust

3,5004,000

4,500

(17.8)(20.3)

(22.9)

hoods shall be rounded. The minimum clearancebetween hoods and combustible construction shallbe the clearance required by the duct system.

506.0 Product-Conveying Ducts.506.1 Materials. Materials used in product-conveying duct systems shall be suitable for theintended use and shall be of metal.

Exceptions:(1) Asbestos-cement, concrete, clay, or ceramic

materials may be used when it is shown thatthese materials will be equivalent to metalducts installed in accordance with thischapter.

(2) Ducts serving a Class 5 system may beconstructed of approved nonmetallic mate-rial when the corrosive characteristics of thematerial being conveyed make a metalsystem unsuitable and when the mixturebeing conveyed is nonflammable.Approved nonmetallic material shall beeither a listed product having aflame-spread index of twenty-five (25) orless and a smoke-developed rating of fifty(50) or less on both inside and outsidesurfaces without evidence of continuedprogressive combustion, or shall have aflame-spread index of twenty-five (25) orless and shall be installed with an automaticfire-sprinkler protection system inside theduct.

(3) Ducts used in central vacuum cleaningsystems within a dwelling unit shall beconstructed of materials in compliance withthe applicable standards referenced inChapter 17. Penetrations of fire walls orfloor-ceiling or roof-ceiling assemblies shallcomply with the Building Code.Copper or ferrous pipes or conduitsextending from within the separationbetween a garage and dwelling unit to thecentral vacuuming unit may be used.

Aluminum ducts shall not be used in systemsconveying flammable vapors, fumes, or explosivedusts, nor in Class 2, 3, or 4 systems. Galvanizedsteel and aluminum ducts shall not be used when thetemperature of the material being conveyed exceeds400˚F (205˚C).

Metal ducts used in Class 5 systems that are notresistant to the corrosiveness of the product shall beprotected with appropriate corrosion-resistant mate-rial.

506.2 Construction. Ducts used for conveying prod-ucts shall be of substantial airtight construction andshall not have openings other than those required foroperation and maintenance of the system. Ductsconstructed of steel shall comply with Table 5-5 or 5-6.

Exceptions:(1) Class 1 product-conveying ducts that

operate at less than four (4) inches (102 mm)water column (995.6 Pa) negative pressureand convey noncorrosive, nonflammable,and nonexplosive materials at temperaturesnot exceeding 250˚F (121˚C) may beconstructed in accordance with Tables 6-1,6-2, 6-3, 6-4, 6-5, 6-7, 6-8, or, with priorapproval, UMC Standard No. 6-2.

(2) Ducts used in central vacuuming systemswithin a dwelling unit shall be constructedof materials in compliance with the appli-cable standards referenced in Chapter 17.Penetrations of fire-resistive walls, orfloor-ceiling or roof-ceiling assemblies shallcomply with the Building Code. Copper orferrous pipes or conduit extending fromwithin the separation between a garage anddwelling unit to the central vacuum unitmay be used.

The use of rectangular ducts conveying particu-lates shall be subject to approval of the building offi-cial. The design of rectangular ducts shall considerthe adhesiveness and buildup of products beingconveyed within the duct.

Aluminum construction may be used in Class 1duct systems only. The thickness of aluminum ductsshall be at least two Brown and Sharpe gaugesthicker than the gauges required for steel ducts setforth in Tables 5-5 and 5-6.506.3 Fittings. Fittings in Class 2, 3, and 4 systemsshall be not less than two gauges thicker than thethickness required for straight runs. Flexible metallicduct may be used for connecting ductwork tovibrating equipment. Duct systems subject to widetemperature fluctuations shall be provided withexpansion joints.

Branches shall connect to main ducts at the largeend of transitions at an angle not exceeding forty-five (45) degrees (0.79 rad).

Except for ducts used to convey noncorrosivevapors with no particulate, accessible cleanouts shallbe provided at ten (10) foot (3,048 mm) intervals andat changes in direction. Access openings shall also beprovided for access to sprinklers and other equip-ment within the duct that require servicing.506.4 Explosion Venting. Ducts conveying explo-sive dusts shall have explosion vents, openings


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protected by antiflashback swing valves, or rupturediaphragms. Openings to relieve explosive forcesshall be located outside the building. When reliefdevices cannot provide sufficient pressure relief,ductwork shall be designed to withstand an internalpressure of not less than 100 pounds per square inch(689 kPa).

If a room or building contains a dust explosionhazard that is external to protected equipment, asdefined in 2.2.3.1 of NFPA 654, such areas shall beprovided with deflagration venting to a safe outsidelocation.506.5 Supports. Spacing of supports for ducts shallnot exceed twelve (12) feet (3,658 mm) for eight (8)inch (203 mm) ducts nor twenty (20) feet (6,096 mm)for larger ducts, unless justified by the design.

506.5.1 Duct supports shall be designed to carrythe weight of the duct half filled with material.Where sprinkler protection is provided in theduct, the hanger’s design shall include theweight of the duct half filled with water or withthe material being conveyed, whichever has thehigher density. Loads shall not be placed onconnecting equipment.

Exception: Where adequate drainage isprovided, the weight of the water shall notrequire consideration.

506.5.2 Hangers and supports exposed to corro-sive atmospheres shall be Type 316 SS or equiva-lent.506.5.3 To avoid vibration and stress on theduct, hangers and supports shall be securelyfastened to the building or structure.506.5.4 Hangers and supports shall be designedto allow for expansion and contraction. [NFPA91:4.5.6]

506.6 Fire Protection. Sprinklers or otherfire-protection devices shall be installed within ductshaving a cross-sectional dimension exceeding ten(10) inches (254 mm) when the duct conveysflammable vapors or fumes. Sprinklers shall beinstalled at twelve (12) foot (3,658 mm) intervals inhorizontal ducts and at changes in direction. Invertical runs, sprinklers shall be installed at the topand at alternate floor levels.506.7 Duct Clearances.

506.7.1 All ductwork and system componentshandling combustible material and operating atless than 140ºF (60ºC) shall have a clearance ofnot less than eighteen (18) inches (457 mm) fromcombustible construction or any combustiblematerial.

Exception No. 1: When the ductworksystem is equipped with an approved auto-matic extinguishing system designed for the

specific hazard, the clearance shall bepermitted to be reduced to six (6) inches(152 mm ) from combustible materials and1/2 inch (13 mm) from combustibleconstruction.Exception No. 2: When the combustiblematerial and construction is protected by theuse of materials or products listed forprotection purposes or in accordance withTable 5-2.506.7.1.1 Spacers and ties for protectionmaterials shall be of noncombustible mate-rial and shall not be used directly behind theduct.506.7.1.2 With all clearance reductionsystems using a ventilated airspace, aircirculation shall be provided as described inTable 5-2. There shall be at least one (1) inch(25 mm) between the wall protector andcombustible walls and ceilings for clearance,reduction systems using a ventilated space.506.7.1.3 Mineral wool batts (blanket orboard) shall have a minimum density ofeight (8) lb./ft.3 (3.6 kq/m3) and have aminimum melting point of 1,500ºF (816ºC).506.7.1.4 Insulation board used as a part ofa clearance-reduction system shall have athermal conductivity of 1 Btu in./ft.2 hrºF(0.14 W/m2 hrºC) or less. Insulation boardshall be formed of noncombustible material.506.7.1.5 There shall be at least one (1) inch(25 mm) between the duct and the wallprotector. In no case shall the clearancebetween the duct and the wall surface bereduced below that shown in Table 5-2.

506.7.2 Duct systems operating at elevatedtemperatures above 140ºF (60ºC) shall haveclearances from combustible building construc-tion or any combustible material of not less thaneighteen (18) inch (457 mm).506.7.3 Where clearance is reduced by using anairspace between the combustible wall and thewall protector, air circulation shall be providedby one of the following methods.

506.7.3.1 Air circulation shall be permittedto be provided by leaving all edges of thewall protector open with at least a one (1)inch (25 mm) airgap.506.7.3.2 If the wall protector is mountedon a single flat wall away from corners, aircirculation shall be permitted to be providedby one of the following:(A) Leaving top and bottom edges open to

circulation by maintaining the one (1)inch (25 mm) airgap.


48

506.4 – 506.7

(B) Leaving top and both side edges opento circulation by maintaining the (1)inch (25 mm) air gap.

506.7.3.3 Wall protectors that cover twowalls in a corner shall be permitted to beopen at the top and bottom edges with atleast a one (1) inch (25 mm) air gap. [NFPA91:4.6.3.3]

506.8 Protection from Physical Damage. Ductsinstalled in locations where they are subject to phys-ical damage shall be protected by suitable guards.506.9 Exhaust Outlets. The termination point forexhaust ducts discharging to the atmosphere shall benot less than the following:

506.9.1 Ducts conveying explosive or flammablevapors, fumes, or dusts: thirty (30) feet (9,144mm) from property line; ten (10) feet (3,048 mm)from openings into the building, six (6) feet(1,829 mm) from exterior walls or roofs; thirty(30) feet (9,144 mm) from combustible walls oropenings into the building that are in the direc-tion of the exhaust discharge; ten (10) feet (3,048mm) above adjoining grade.506.9.2 Other product-conveying outlets: ten(10) feet (3,048 mm) from property line; three (3)feet (914 mm) from exterior wall or roof; ten (10)feet (3,048 mm) from openings into the building;ten (10) feet (3,048 mm) above adjoining grade.

EXHAUST SYSTEMS Table 5-2 – 506.9

49

TABLE 5-2Reduction of Duct Clearance with Specified Forms of Protection

Clearance reduction applied to and covering all combustible Minimum Allowable Reductionsurfaces with the distance specified as required clearance in Clearance (%)with no protection in 506.7.2

Form of Protection As Wall Protector As Ceiling Protector(a) 3-1/2 in. (90 mm) thick masonry wall without ventilated airspace 33 ––(b) 1/2 in. (13 mm) thick noncombustible insulation board over 1 in. 50 33

(25.4 mm) glass fiber or mineral wool batts without ventilated airspace(c) 0.024 in. (0.61 mm) (No. 24 gauge) sheet metal over 1 in. (25.4 mm) glass 66 66

fiber or mineral wool batts reinforced with wire, or equivalent, on rear facewith at least a 1 in. (25.4 mm) air gap

(d) 3-1/2 in (90 mm) thick masonry wall with at least a 1 in (25.4 mm) air gap 66 ––(e) 0.024 in. (0.61 mm) (No. 24 gauge) sheet metal with at least a 1 in. (25.4 mm) 66 50

air gap(f) 1/2 in. (13 mm) thick noncombustible insulation board with at least a 1 in. 66 50

(25.4 mm) air gap(g) 0.024 in. (0.61mm) (No. 24 gauge) sheet metal with ventilated airspace over 66 50

0.024 in. (0.61 mm) (No. 24 gauge) sheet metal with at least a 1 in. (25.4 mm)air gap

(h) 1 in. (25.4 mm) glass fiber or mineral wool batts sandwiched between two 66 50sheets 0.024 in. (0.61 mm) (No. 24 gauge) sheet metal with at least a 1 in.(25.4 mm) air gap

Extent of protection required to reduce clearances from ducts.


50

Table 5-3

TABLE 5-3Reduction of Clearances with Specified Forms of Protection

[NFPA 54: Table 10.2.3(b)]Where the required clearance with no protection from appliance, vent connector, or single-

wall metal pipe is:36 in. 18 in. 12 in. 9 in. 6 in.

Allowable Clearances with Specified Protection (in.)Type of protection applied toand covering surfaces ofcombustible material withinthe distance specified as therequired clearance with noprotection [See Figures 5-4through 5-6.]

Use Col. 1 for clearances above appliance or horizontal connector. Use Col. 2 for clearances fromappliances, vertical connector, and single-wall metal pipe.

AboveCol. 1

SidesandRearCol. 2

AboveCol. 1

SidesandRearCol. 2

AboveCol. 1

SidesandRearCol. 2

AboveCol. 1

SidesandRearCol. 2

AboveCol. 1

SidesandRearCol. 2

(1) 3-1/2 in. thickmasonrywall without ventilatedair space

-- 24 -- 12 -- 9 -- 6 -- 5

(2) 1/2 in. insulation boardover 1 in. glass fiber ormineral wool batts

24 18 12 9 9 6 6 5 4 3

(3) 0.024 sheet metal over 1in. glass fiber or mineralwool batts reinforcedwith wire on rear facewith ventilated air space

18 12 9 6 6 4 5 3 3 3

(4) 3-1/2 in. thickmasonrywall with ventilated airspace

-- 12 -- 6 -- 6 -- 6 -- 6

(5) 0.024 sheet metal withventilated air space

18 12 9 6 6 4 5 3 3 2

(6) 1/2 in. thick insulationboardwith ventilated airspace

18 12 9 6 6 4 5 3 3 3

(7) 0.024 sheet metal withventilated air space over0.024 sheet metal withventilated air space

18 12 9 6 6 4 5 3 3 3

(8) 1 in. glass fiber ormineral wool batts sand-wiched between twosheets 0.024 sheet metalwith ventilated air space

18 12 9 6 6 4 5 3 3 3

Notes:1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility ofservicing.

2 Clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disre-garding any intervening protection applied to the combustible material.

3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector.4 Where clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figure5-5 and Figure 5-6.]

5 There shall be not less than one (1) in. (25 mm) between clearance reduction systems and combustible walls and ceilings for reduction systemsusing a ventilated air space.

6 Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum one (1) inch (25 mm) air gap. To provideadequate air circulation, the bottom and top edges, or only the side and top edges, or edges shall be left open.

7 Mineral wool batts (blanket or board) shall have a minimum density of eight (8) lb/ft.3 (128 kg/m3) and a minimum melting point of 1,500ºF(816ºC).

8 Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 Btu in./ft2/h-ºF (0.144 W/m-K) or less.9 There shall be not less than (1) inch (25 mm) between the appliance and the protector. In no case shall the clearance between the appliance andthe combustible surface be reduced below that allowed in this table.

10 Clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.11 Listed single-wall connectors shall be installed in accordance with the terms of their listing and the manufacturer’s instructions.1 in. = 25.4 mm

Part II – Commercial Hoods and KitchenVentilation.

507.0 General Requirements.507.1 Cooking equipment used in processesproducing smoke or grease-laden vapors shall beequipped with an exhaust system that complies withall the equipment and performance requirements ofthis standard, and all such equipment and perfor-mance shall be maintained per this standard duringall periods of operation of the cooking equipment.Specifically, the following equipment shall be kept ingood working condition:(A) Cooking equipment(B) Hoods(C) Ducts (if applicable)(D) Fans(E) Fire suppression systems(F) Special effluent or energy control equipment

All airflows shall be maintained. Maintenanceand repairs shall be performed on all components atintervals necessary to maintain these conditions.

507.1.1 Cooking equipment that has been listedin accordance with UL 197 or an equivalent stan-dard for reduced emissions shall not be requiredto be provided with an exhaust system. [NFPA96:4.1.1.1*]507.1.2 The listing evaluation of cooking equip-ment covered by Section 507.1.1 shall demon-strate that the grease discharge at the exhaustduct of a test hood placed over the applianceshall not exceed 5 mg/m3 when operated with atotal airflow of 0.236 cubic meters per second(500 cfm). [NFPA 96:4.1.1.2]507.1.3 The responsibility for inspection, main-tenance, and cleanliness of the ventilationcontrol and fire protection of the commercialcooking operations shall be the ultimate respon-sibility of the owner of the system provided thatthis responsibility has not been transferred inwritten form to a management company or otherparty. [NFPA 96:4.1.5]507.1.4 All solid-fuel cooking equipment shallcomply with the requirements of Section 517.0.507.1.5 Multiple-tenancy applications shallrequire the concerted cooperation of design,installation, operation, and maintenance respon-sibilities by tenants and by the building owner.507.1.6 All interior surfaces of the exhaustsystem shall be accessible for cleaning andinspection purposes.

507.1.7 Cooking equipment used in fixed,mobile, or temporary concessions, such astrucks, buses, trailers, pavilions, tents, or anyform of roofed enclosure, shall comply with thisstandard unless all or part of the installation isexempted by the Authority Having Jurisdiction.

507.2 Clearance.507.2.1 Where enclosures are not required,hoods, grease removal devices, exhaust fans,and ducts shall have a clearance of at least eigh-teen (18) inches (457 mm) to combustible mate-rial, three (3) inches (76 mm) to limited-combustible material, and zero (0) inches (0 mm)to noncombustible material. [NFPA 96:4.2.1]507.2.2 Where a hood, duct, or grease removaldevice is listed for clearances less than thoserequired in 507.2.1, the listing requirements shallbe permitted. [NFPA 96:4.2.2]507.2.3 Clearance Reduction.

507.2.3.1 Where a clearance reductionsystem consisting of 0.013 in. (0.33 mm) (28gauge) sheet metal spaced out one (1) inch(25 mm) on noncombustible spacers isprovided, there shall be a minimum of nine(9) inches (229 mm) clearance to combustiblematerial. [NFPA 96:4.2.3.1]507.2.3.2 Where a clearance reductionsystem consisting of 0.027 in. (0.69 mm) (22gauge) sheet metal on one (1) inch (25 mm)mineral wool batts or ceramic fiber blanketreinforced with wire mesh or equivalentspaced out one (1) inch (25 mm) on non-combustible spacers is provided, there shallbe a minimum of three (3) inches (76 mm)clearance to combustible material. [NFPA96:4.2.3.2]507.2.3.3 Zero clearance to limited-combustible materials shall be permittedwhere protected by metal lath and plaster,ceramic tile, quarry tile, other non-combustible materials or assembly ofnoncombustible materials, or materials andproducts that are listed for the purpose ofreducing clearance. [NFPA 96:4.2.3.3]

507.2.4 Clearance Integrity.507.2.4.1 In the event of damage, the mate-rial or product shall be repaired andrestored to meet its intended listing or clear-ance requirements and shall be acceptable tothe authority having jurisdiction. [NFPA96:4.2.4.1]507.2.4.2 In the event of a fire within akitchen exhaust system, the duct and itsenclosure (rated shaft, factory-built grease


51

duct enclosure, or field-applied grease ductenclosure) shall be inspected by qualifiedpersonnel to determine whether the ductand protection method are structurallysound, capable of maintaining their fireprotection function, and in compliance withthis standard for continued operation.[NFPA 96:4.2.4.2]507.2.4.3 Protection shall be provided onthe wall from the bottom of the hood to thefloor, or to the top of the noncombustiblematerial extending to the floor, to the samelevel as required in 507.2.1. [NFPA96:4.2.4.3]507.2.4.4 The protection methods for ductsto reduce clearance shall be applied to thecombustible or limited-combustible construc-tion, not to the duct itself. [NFPA 96:4.2.4.4]

507.2.5 Factory-built grease duct enclosuresshall be protected with a through-penetrationfirestop system classified in accordance withASTM E814 having an "F" and "T" rating equal tothe fire resistance rating of the assembly beingpenetrated from the point at which the ductpenetrates a ceiling, wall or floor to the outletterminal, and the factory-built grease ductprotection system shall be listed in accordancewith UL 2221, Standard for Tests of Fire ResistiveGrease Duct Enclosure Assemblies and installed inaccordance with the manufacturer's instructionsand the listing requirements. [NFPA 96:4.3.3,4.3.3.1, 4.3.3.2]507.2.6 Field-applied grease duct enclosuresshall be protected with a through penetrationfirestop system classified in accordance withASTM E814 having an "F" and "T" rating equal tothe fire resistance rating of the assembly beingpenetrated. The surface of the field fabricatedgrease duct shall be continuously covered on allsides from the point at which the duct enclosurepenetrates a ceiling, wall or floor to the outletterminal, and listed in accordance with ASTM E2336 Standard Test Methods for Fire resistive GreaseDuct Enclosure Systems, and installed in accor-dance with the manufacturer's instructions andthe listing requirements. [NFPA 96:4.3.1, 4.3.1.1,4.3.1.2]507.2.7 Field-applied grease duct enclosuresand factory-built grease duct enclosures shalldemonstrate that they provide sufficientmechanical and structural integrity, resiliency,and stability when subjected to expectedbuilding environmental conditions, duct move-ment under general operating conditions, andduct movement due to fire conditions. [NFPA96:4.3.4]

507.2.7.1Measures shall be taken to preventphysical damage to any material or productused for the purpose of reducing clearances.

Exception: When the duct is protectedwith a field-applied grease duct enclo-sure or factory-built grease duct enclo-sure.

507.2.7.2 The specifications of material,gauge, and construction of the duct used inthe testing and listing of field-applied greaseduct enclosures and factory-built greaseduct enclosures shall be included asminimum requirements in their listing andinstallation documentation. [NFPA 96:4.3.5]507.2.7.3 The following clearance optionsfor which field-applied grease duct enclo-sures and factory-built grease duct enclo-sures have been successfully evaluated shallbe clearly identified in their listing andinstallation documentation and on theirlabel: [NFPA 96:4.3.6](1) Open combustible clearance at manu-

facturer’s requested dimensions. [NFPA96:4.3.6(1)]

(2) Closed combustible clearance at manu-facturer’s requested dimensions, with orwithout specified ventilation. [NFPA96:4.3.6(2)]

(3) Rated shaft clearance at manufacturer’srequested dimensions, with or withoutspecified ventilation. [NFPA 96:4.3.6(3)]

507.2.8 A duct shall be permitted to contactnoncombustible floors, interior walls, and othernoncombustible structures or supports, but itshall not be in contact for more than fifty (50)percent of its surface area per each lineal foot ofcontact length. [NFPA 96:4.4.1]

507.2.8.1 Where duct contact must exceedthe requirements of 507.2.8, the duct shall beprotected from corrosion. [NFPA 96:4.4.2]507.2.8.2 Where the duct is listed for zeroclearance to combustibles or otherwiseprotected with a material or product listedfor the purpose of reducing clearance tozero, the duct shall be permitted to exceedthe contact limits of 507.2.8 without addi-tional corrosion protection. [NFPA 96:4.4.3]

507.2.9 Clearances between the duct and inte-rior surfaces of enclosures shall meet therequirements of Section 507.2.

507.3 A drawing(s) of the exhaust system installa-tion along with a copy of operating instructions forsubassemblies and components used in the exhaust


52

507.2 – 507.3

system, including electrical schematics, shall beavailable on the premises.507.4 If required by the Authority Having Jurisdic-tion, notification in writing shall be given of anyalteration, replacement, or relocation of any exhaustor extinguishing system or part thereof or cookingequipment. Satisfaction shall be provided to theAuthority Having Jurisdiction that the completeexhaust system as addressed in this standard isinstalled and operable in accordance with theapproved design and the manufacturer’s instruc-tions.

508.0 Hoods.508.1 Where Required. Hoods shall be installed ator above all commercial-type deep fat fryers,broilers, fry grills, steam-jacketed kettles, hot-topranges, ovens, barbecues, rotisseries, dishwashingmachines, and similar equipment that producescomparable amounts of steam, smoke, grease, orheat in a food-processing establishment. For thepurpose of this section, a food-processing establish-ment shall include any building or portion thereofused for the processing of food, but shall not includea dwelling unit.

508.1.1 Construction. The hood or that portionof a primary collection means designed forcollecting cooking vapors and residues shall beconstructed of and be supported by steel not lessthan 0.043 inch (1.09 mm) (No. 18 MSG) in thick-ness, stainless steel not less than 0.037 inch (0.94mm) (No. 20 MSG) in thickness, or otherapproved material of equivalent strength andfire and corrosion resistance.

Exceptions:(1) Listed exhaust hoods with or without

exhaust dampers.(2) Type II hoods shall be constructed of at

least 0.024 inch (0.61 mm) (No. 24 gaugesteel. Hoods constructed of copper shallbe of copper sheets weighing at leasttwenty-four (24) ounces per square foot(7.32 kg/m2). Joints and seams shall besubstantially tight. Solder shall not beused except for sealing a joint or seam.

All hoods shall be secured in place bynoncombustible supports.508.1.2 Wall mounted exhaust hood assembliesshall be tight fitting against the back wall as tonot permit passage of grease vapor behind thehood, or between the back wall and the hoodassembly. [NFPA 96:5.1.13]

508.2 All seams, joints, and penetrations of the hoodenclosure that direct and capture grease-ladenvapors and exhaust gases shall have a liquid-tightcontinuous external weld to the hood’s lower outer-most perimeter. [NFPA 96:5.1.2]

508.2.1 Seams, joints, and penetrations of thehood shall be permitted to be internally welded,provided that the weld is formed smooth orground smooth, so as to not trap grease, and iscleanable. [NFPA 96:5.1.3]508.2.2 Internal hood joints, seams, filtersupport frames, and appurtenances attachedinside the hood shall be sealed or otherwisemade grease-tight. [NFPA 96:5.1.4]508.2.3 Penetrations shall be permitted to besealed by devices that are listed for such use andwhose presence does not detract from the hood’sor duct’s structural integrity. [NFPA 96:5.1.5]508.2.4 Listed exhaust hoods with or withoutexhaust dampers shall be permitted to beconstructed of materials required by the listing.[NFPA 96:5.1.6]508.2.5 Listed exhaust hoods with or withoutexhaust dampers shall be permitted to be assem-bled in accordance with the listing requirements.[NFPA 96:5.1.7]508.2.6 Eyebrow-type hoods over gas or electricovens shall be permitted to have a ductconstructed as required in Section 510.0 from theoven flue(s) connected to the hood canopyupstream of the exhaust plenum as shown inFigure 5-1. [NFPA 96:5.1.8.1]508.2.7 The duct connecting the oven flue(s) tothe hood canopy shall be connected with acontinuous weld or have a duct-to-duct connec-tion. [See Figure 5-6(a) through Figure 5-6(d)][NFPA 96:5.1.8.2]508.2.8 Insulation materials other than electricalinsulation shall have a flame spread rating of 25or less when tested in accordance with UL 723.[NFPA 96:5.1.9]508.2.9 Adhesives or cements used in the instal-lation of insulating materials shall comply withthe requirements of 508.2.8, when tested withthe specific insulating material. [NFPA 96:5.1.10]508.2.10 Penetrations shall be sealed with listeddevices in accordance with the requirements of508.2.11. [NFPA 96:5.1.11]508.2.11 Devices that require penetration of thehood, such as pipe and conduit penetrationfittings and fasteners, shall be listed in accor-dance with UL 1978. [NFPA 96:5.1.12]


53

508.3 Insulation materials other than electrical insu-lation shall have a flame-spread rating of twenty-five(25) or less when tested in accordance with UL 723,Standard for Test for Surface Burning Characteristics ofBuilding Materials. Adhesives or cements used in theinstallation of insulating materials shall comply withthe preceding requirements when tested with thespecific insulating material.508.4 Hood Size. Hoods shall be sized according tothe following calculations and configured to providefor the capture and removal of grease-laden vapors.(See Section 511.2.3)

508.4.1 Canopy Size and Location. Forcanopy-type commercial cooking hoods, theinside edge thereof shall overhang or extend ahorizontal distance of not less than six (6) inches(152 mm) beyond the edge of the cookingsurface on all open sides, and the verticaldistance between the lip of the hood and thecooking surface shall not exceed four (4) feet(1,219 mm).

Exception: Listed exhaust hoods are to beinstalled in accordance with the terms oftheir listings and the manufacturer’s instal-lation instructions.508.4.1.1 Capacity of Hoods. Canopy-typecommercial cooking hoods shall exhaustthrough the hood a minimum quantity of airdetermined by application of the followingformulas:WHERE:A = the horizontal surface area of the hood,in square feet (m2).P = that part of the perimeter of the hoodthat is open, in feet (mm).

D = distance in feet (mm) between the lowerlip of the hood and the cooking surface.Q = quantity of air, in cubic feet per minute(L/s).

When cooking equipment is installedback to back and is covered by a commonisland-type hood, the airflow required maybe calculated using the formula for threesides exposed. Type II hood airflow require-ments shall be in accordance with therequirements for low-temperature appliancehoods.508.4.1.2 The minimum airflow for solid-fuel cooking equipment, grease-burningcharbroilers, and undefined equipment shallbe:Number of Exposed Sides Formula4 (island or central hood) Q = 300A3 or less Q = 200AAlternate formula Q = 100PD508.4.1.3 Type I hoods when the cookingequipment includes high-temperature appli-ances such as deep-fat fryers:Number of Exposed Sides Formula4 (island or central hood) Q = 150A3 or less Q = 100AAlternate formula Q = 100PD508.4.1.4 Type I hoods where the cookingequipment includes medium-temperatureappliances such as rotisseries, grills, andranges:Number of Exposed Sides Formula4 (island or central hood) Q = 100A3 or less Q = 75AAlternate formula Q = 50PD508.4.1.5 Type I hoods where the cookingequipment includes low-temperature appli-ances such as medium-to-low-temperatureranges, roasters, roasting ovens, pastryovens, and equipment approved for useunder a Type II hood, such as pizza ovens:Number of Exposed Sides Formula4 (island or central hood) Q = 75A3 or less Q = 50AAlternate formula Q = 50PD

Exception: Listed exhaust hoods are tobe installed in accordance with theterms of their listing and the manufac-turer’s installation instructions.

508.4.2 Capacity for Noncanopy Hoods. Inaddition to all other requirements for hoods

FIGURE 5-1 Typical Section of Eyebrow-TypeHood. [NFPA 96:5.1.8.1]


54

Figure 5-1 – 508.4

specified in this section, the volume of airexhausting through a noncanopy-type hood tothe duct system shall be not less than 300 cubicfeet per minute per lineal foot (465 L/s per m) ofcooking equipment. Listed noncanopy exhausthoods and filters shall be sized and installed inaccordance with the terms of their listing and themanufacturer’s installation instructions.

Exception: Listed hood assemblies designedand installed specifically for the intendeduse.

508.5 Exhaust Hood Assemblies with IntegratedSupply-Air Plenums.

508.5.1 The construction and size of exhausthood assemblies with integrated supply airplenums shall comply with the requirements ofSections 508.1 and 508.4. [NFPA 96:5.3.1]508.5.2 The construction of the outer shell or theinner exhaust shell shall comply with Section508.1. [NFPA 96:5.3.2]508.5.3 Where the outer shell is welded, theinner shell shall be of grease-tight construction.[NFPA 96:5.3.3]508.5.4 Fire Dampers.

508.5.4.1 A fire-actuated damper shall beinstalled in the supply air plenum at eachpoint where a supply air duct inlet or asupply air outlet penetrates the continu-ously welded shell of the assembly. [NFPA96:5.3.4.1]508.5.4.2 The fire damper shall be listed forsuch use or be part of a listed exhaust hoodwith or without exhaust damper. [NFPA96:5.3.4.2]508.5.4.3 The actuation device shall have amaximum temperature rating of 141°C(286°F). [NFPA 96:5.3.4.3]

508.5.5 Supply air plenums that discharge airfrom the face rather than from the bottom or intothe exhaust hood and that are isolated from theexhaust hood by the continuously welded shellextending to the lower outermost perimeter ofthe entire hood assembly shall not require a fire-actuated damper. [NFPA 96:5.3.4.4]

508.6 Listed Hood Assemblies. Listed hood assem-blies shall be installed in accordance with the termsof their listing and the manufacturer’s instructions.[NFPA 96:5.4.1] Listed hood assemblies shall betested in accordance with UL 710 or equivalent.[NFPA 96:5.4.2]508.7 Solid-Fuel Hood Assemblies. Where solid-fuel cooking equipment is to be used, the solid-fuelhood assembly shall comply with Section 517.0.

508.8 Listed Ultra-Violet Hoods. Listed ultra-violethoods shall be installed and maintained in accor-dance with the terms of their listing and the manu-facturer’s instructions. [NFPA 96:5.5]508.9 Exhaust Outlets. An exhaust outlet within anunlisted hood shall be located so as to optimize thecapture of particulate matter. Each outlet shall servenot more than a twelve (12) foot (3,658 mm) sectionof an unlisted hood.

509.0 Grease Removal Devices in Hoods.509.1 Grease Removal Devices. Listed greasefilters, baffles, or other approved grease removaldevices for use with commercial cooking equipmentshall be provided. Listed grease filters shall be testedin accordance with UL 1046, Grease Filters forExhaust Ducts. Mesh filters shall not be used.509.2 Installation.

509.2.1 The distance between the greaseremoval device and the cooking surface shall beas great as possible but not less than eighteen(18) inches (457 mm). [NFPA 96:6.2.1.1]509.2.2 Where grease removal devices are usedin conjunction with charcoal or charcoal-typebroilers, including gas or electrically heatedcharbroilers, a minimum vertical distance of four(4) feet (1,219 mm) shall be maintained betweenthe lower edge of the grease removal device andthe cooking surface. [NFPA 96:6.2.1.2]

Exception No. 1: Grease removal devicessupplied as part of listed hood assembliesshall be installed in accordance with theterms of the listing and the manufacturer’sinstructions. [NFPA 96:6.2.1.5]Exception No. 2: For cooking equipmentwithout exposed flame and where flue gasesbypass grease removal devices, theminimum vertical distance shall bepermitted to be reduced to not less than six(6) inches (152 mm). [NFPA 96:6.2.1.3]Exception No. 3: Where a grease removaldevice is listed for separation distances lessthan those required in 509.2.1 and 509.2.2,the listing requirements shall be permitted.[NFPA 96:6.2.1.4]

509.2.3 Grease Removal Device Protection.Grease removal devices shall be protected fromcombustion gas outlets and from direct flameimpingement occurring during normal opera-tion of cooking appliances producing high fluegas temperatures, such as deep-fat fryers orupright or high broilers (salamander broilers),where the distance between the grease removal


55

device and the appliance flue outlet (heatsource) is less than eighteen (18) inches (457mm). [NFPA 96:6.2.2.1]

509.2.3.1 This protection shall be permittedto be accomplished by the installation of asteel or stainless steel baffle plate betweenthe heat source and the grease removaldevice. [NFPA 96:6.2.2.2]509.2.3.2 The baffle plate shall be sized andlocated so that flames or combustion gasesshall travel a distance not less than eighteen(18) inches (457 mm) from the heat source tothe grease removal device. [NFPA 96:6.2.2.3]509.2.3.3 The baffle shall be located not lessthan six (6) inches (152 mm) from the greaseremoval devices. [NFPA 96:6.2.2.4]

509.2.4 Grease Filters. Grease filters shall belisted and constructed of steel or listed equiva-lent material and shall be of rigid constructionthat will not distort or crush under normal oper-ation, handling, and cleaning conditions. [NFPA96:6.2.3.1 and 6.2.3.2]

509.2.4.1 Filters shall be tight fitting andfirmly held in place and grease filters shallbe arranged so that all exhaust air passesthrough the grease filters. [NFPA 96:6.2.3.3]509.2.4.2 Filters shall be easily accessible andremovable for cleaning. [NFPA 96:6.2.3.4]509.2.4.3 Filters shall be installed at anangle not less than forty-five (45) degreesfrom the horizontal. [NFPA 96:6.2.3.5]

509.2.5 Grease Drip Trays. Filters shall beequipped with a drip tray beneath their loweredges. [NFPA 96:6.2.4.1]

509.2.5.1 The tray shall be kept to theminimum size needed to collect grease andshall be pitched to drain into an enclosedmetal container having a capacity notexceeding one (1) gallon (3.785 L) [NFPA96:6.2.4.2, and 6.2.4.3].

509.2.6 Grease Filter Orientation. Grease filtersthat require a specific orientation to drain greaseshall be clearly so designated, or the hood shallbe constructed so that filters cannot be installedin the wrong orientation. [NFPA 96:6.2.5]

509.3 Solid-Fuel Grease Removal Devices.Where solid-fuel cooking equipment is providedwith grease removal devices, these devices shallcomply with Section 517.0.

510.0 Exhaust Duct Systems.510.1 General.

510.1.1 Ducts shall not pass through fire wallsor fire partitions.

510.1.2 All ducts shall lead as directly as is prac-ticable to the exterior of the building, so as not tounduly increase any fire hazard.510.1.3 Duct systems shall not be interconnectedwith any other building ventilation or exhaustsystem.510.1.4 All ducts shall be installed withoutforming dips or traps that might collect residues.In manifold (common duct) systems, the lowestend of the main duct shall be connected flush onthe bottom with the branch duct. Duct systemsserving a Type I hood shall be so constructedand installed that grease cannot become pock-eted in any portion thereof, and the system shallslope not less than 1/4 inch per lineal foot (21mm/m) toward the hood or toward anapproved grease reservoir. Where horizontalducts exceed seventy-five (75) feet (22,860 mm)in length, the slope shall be not less than one (1)inch per lineal foot (83 mm/m).510.1.5 Openings required for accessibility shallcomply with Section 510.3.510.1.6 A sign shall be placed on all accesspanels stating the following:ACCESS PANEL––DO NOT OBSTRUCT510.1.7 Duct bracing and supports shall be ofnoncombustible material, securely attached tothe structure and designed to carry gravity andlateral loads within the stress limitations of theBuilding Code. Bolts, screws, rivets, and othermechanical fasteners shall not penetrate ductwalls.510.1.8 Ducts, Non-Grease. Ducts andplenums serving Type II hoods shall beconstructed of rigid metallic materials as setforth in Chapter 6. Duct bracing and supportsshall comply with Chapter 6. Ducts subject topositive pressure shall be adequately sealed.

510.2 Clearance.510.2.1 Clearance between ducts andcombustible materials shall be provided in accor-dance with the requirements of Section 507.2.510.2.2 Listed grease ducts shall be installed inaccordance with the terms of their listings andmanufacturers’ instructions.

510.3 Openings.510.3.1 Openings shall be provided at the sidesor at the top of the duct, whichever is moreaccessible, and at changes of direction. Openingsshall be protected by approved access panelsthat comply with Section 510.3.4.5.

Exception: Openings shall not be requiredin portions of the duct that are accessiblefrom the duct entry or discharge.


56

509.2 – 510.3

510.3.2 For hoods with dampers in the exhaustor supply collar, an access panel for cleaning andinspection shall be provided in the duct or thehood collar. This access panel shall be as close tothe hood as possible but shall not exceed eigh-teen (18) inches (457 mm).

Exception: Dampers that are accessible fromunder the hood.

510.3.3 Exhaust fans with ductwork connectedto both sides shall have access for cleaning andinspection within three (3) feet (914 mm) of eachside of the fan. [NFPA 96:7.3.7]510.3.4 Openings in Ducts. Openings shallconform with Sections 510.3.4.1 through510.3.4.5. [NFPA 96:7.4]

510.3.4.1 Horizontal Ducts. On horizontalducts, at least one 20 inch by 20 inch (508mm x 508 mm) opening shall be providedfor personnel entry. [NFPA 96:7.4.1.1]

510.3.4.1.1 Horizontal ducting shall besecured sufficiently to allow for theweight of personnel entry into the duct.Where an opening of this size is notpossible, openings large enough topermit thorough cleaning shall beprovided at twelve (12) feet (3,658 mm)intervals. [NFPA 96:7.4.1.2]510.3.4.1.2 Openings on horizontalgrease duct systems shall be providedwith safe access and a work platformwhen not easily accessible from a 10 feet(3 m) stepladder. [NFPA 96:7.4.1.3]510.3.4.1.3 Support systems for hori-zontal grease duct systems twenty-four(24) inches (609 mm) and larger in anycross-sectional dimension shall bedesigned for the weight of the ductworkplus 363 kg (800 lb) at any point in theduct systems. [NFPA 96:7.4.1.4]

510.3.4.2 On nonlisted ductwork, the edgeof the opening shall be not less than 1-1/2inch (38.1 mm) from all outside edges of theduct or welded seams. [NFPA 96:7.4.1.5]510.3.4.3 Vertical Ducts. On vertical duct-work where personnel entry is possible,access shall be provided at the top of thevertical riser to accommodate descent.[NFPA 96:7.4.2.1]

510.3.4.3.1 Where personnel entry isnot possible, adequate access forcleaning shall be provided on eachfloor. [NFPA 96:7.4.2.2]

510.3.4.4 Access Panels. Access panelsshall be of the same material and thicknessas the duct (Section 510.5.1). Access panelsshall have a gasket or sealant that is ratedfor 1,500°F (815.6°C) and shall be grease-tight. Fasteners, such as bolts, weld studs,latches, or wing nuts, used to secure theaccess panels shall be carbon steel or stain-less steel and shall not penetrate duct walls.

Exception: Listed grease duct accessdoor assemblies (access panels) shall beinstalled in accordance with their termsof the listings and the manufacturer'sinstructions.

510.3.4.5 Openings for installation,servicing, and inspection of listed fireprotection system devices and for ductcleaning shall be provided in ducts andenclosures and shall conform to the require-ments of 510.3. Enclosure openings requiredto reach access panels in the ductwork shallbe large enough for the removal of theaccess panel.

510.4 Listed Grease Ducts. Listed grease ductsshall be installed in accordance with the terms of thelisting and the manufacturer’s instructions.510.5 Other Grease Ducts. Other grease ducts shallcomply with the requirements of this section.

510.5.1 Materials. Ducts shall be constructed ofand supported by carbon steel not less than0.054 inch (1.37 mm) (No. 16 MSG) in thicknessor stainless steel not less than 0.043 inch (1.09mm) (No. 18 MSG) in thickness.510.5.2 Installation.

510.5.2.1 All seams, joints, penetrations, andduct-to-hood collar connections shall have aliquid-tight continuous external weld.

Exception No. 1: Duct-to-hood collarconnections as shown in Figure 5-2 shallbe permitted.Exception No. 2: Penetrations shall bepermitted to be sealed by other listeddevices that are tested to be grease-tightand are evaluated under the sameconditions of fire severity as the hood orenclosure of listed grease extractors andwhose presence does not detract fromthe hood's or duct's structural integrity.Exception No. 3: Internal welding shallbe permitted, provided the joint isformed or ground smooth and is readilyaccessible for inspection.


57

510.5.2.2 Overlapping duct connections ofeither the telescoping or the bell type shall beused for welded field joints, not butt-weldconnections. The inside duct section shallalways be uphill of the outside duct section.The difference between inside dimensions ofoverlapping sections shall not exceed 1/4inch (6.4 mm). The overlap shall not exceedtwo (2) inches (50.8 mm). (See Figure 5-3.)

510.6 Exterior Installations.510.6.1 The exterior portion of the ductworkshall be vertical wherever possible and shallbe installed and adequately supported on theexterior of a building. Bolts, screws, rivets,and other mechanical fasteners shall notpenetrate duct walls. Clearance of any ductsshall comply with Section 507.2.510.6.2 All ducts shall be protected on theexterior by paint or other suitable weather-protective coating or shall be constructed ofnoncorrosive stainless steel. Ductworksubject to corrosion shall have minimalcontact with the building surface.

510.7 Interior Installations.510.7.1 In all buildings more than one story inheight, and in one-story buildings where the roof-ceiling assembly is required to have a fire resis-tance rating, the ducts shall be enclosed in acontinuous enclosure extending from the lowestfire-rated ceiling or floor above the hood, throughany concealed spaces, to or through the roof so asto maintain the integrity of the fire separations

required by the applicable Building Code provi-sions. The enclosure shall be sealed around theduct at the point of penetration of the lowest fire-rated ceiling or floor above the hood in order tomaintain the fire resistance rating of the enclosureand shall be vented to the exterior of the buildingthrough weather-protected openings.

Exception: The continuous enclosure provi-sions shall not be required where a field-applied grease duct enclosure or a factory-built grease duct enclosure (see Section507.2.3) is protected with a listed duct-through-penetration protection systemequivalent to the fire resistance rating of theassembly being penetrated, and the materialsare installed in accordance with the condi-tions of their listings and the manufacturers’instructions and are acceptable to theAuthority Having Jurisdiction.

510.7.2 The enclosure required in Section 510.7.1shall conform to Sections 510.7.2.1 through 510.7.2.3.

FIGURE 5-2 Permitted Duct-to-Hood CollarConnection. [NFPA 96:7.5.2.2]

FIGURE 5-3 Telescoping and Bell-Type DuctConnections. [NFPA 96:7.5.5.1(a)(b)]


58

Figure 5-2 – 510.7

510.7.2.1 If the building is less than fourstories in height, the enclosure wall shallhave a fire resistance rating of not less thanone (1) hour.510.7.2.2 If the building is four stories ormore in height, the enclosure wall shall havea fire resistance rating of not less than two(2) hours.510.7.2.3 Clearance from the duct or theexhaust fan to the interior surface of enclo-sures of combustible construction shall be notless than eighteen (18) inches (457 mm), andclearance from the duct to the interior surfaceof enclosures of noncombustible or limited-combustible construction shall be not lessthan six (6) inches (152 mm). Provisions forreducing clearances as described in Section507.2 are not applicable to enclosures.

Exception: Clearance from the outersurfaces of field-applied grease ductenclosures and factory-built grease ductenclosures to the interior surfaces ofconstruction installed around them shallbe permitted to be reduced where thefield-applied grease duct enclosurematerials and the factory-built greaseduct enclosures are installed in accor-dance with the conditions of their list-ings and the manufacturers’ instruc-tions and are acceptable to theAuthority Having Jurisdiction.

510.7.3 For field-applied grease duct enclosuresand factory-built grease duct enclosures, thematerials and products shall conform to Sections510.7.3.1 through 510.7.3.3.

510.7.3.1 Field-applied grease duct enclo-sures and factory-built grease duct enclo-sures shall demonstrate that they providesufficient mechanical and structuralintegrity, resiliency, and stability whensubjected to expected building environ-mental conditions, duct movement undergeneral operating conditions, and ductmovement due to interior and exterior fireconditions.510.7.3.2Measures shall be taken to preventphysical damage to any covering or enclo-sure material. Any damage to the coveringor enclosure shall be repaired and thecovering or enclosure restored to meet itsintended listing and fire-resistive rating andto be acceptable to the Authority HavingJurisdiction.

510.7.3.3 In the event of a fire within akitchen exhaust system, the duct, the enclo-sure, or the covering directly applied to theduct shall be inspected by qualifiedpersonnel to determine whether the duct,the enclosure, and the covering directlyapplied to the duct are structurally sound,capable of maintaining their fire protectionfunctions, suitable for continued operation,and acceptable to the Authority HavingJurisdiction.

510.7.4 For listed grease ducts, see Section 510.4.510.7.5 If openings in the enclosure walls areprovided, they shall be protected by approvedself-closing fire doors of proper rating. Firedoors shall be installed in accordance withNFPA 80, Standard for Fire Doors and FireWindows. Openings on other listed materials orproducts shall be clearly identified and labeledaccording to the terms of the listing and themanufacturer's instructions and shall be accept-able to the Authority Having Jurisdiction. Thepanels shall be readily accessible.510.7.6 Each duct system shall constitute anindividual system serving only exhaust hoods inone fire zone on one floor. Multiple ducts shallnot be permitted in a single enclosure unlessacceptable to the Authority Having Jurisdiction.

510.8 Termination of Exhaust System.510.8.1 The exhaust system shall terminate asfollows:(A) Outside the building with a fan or duct.(B) Through the roof, or to the roof from

outside, as in Section 510.8.2, or through awall, as in Section 510.8.3.

510.8.2 Rooftop Terminations.510.8.2.1 Rooftop terminations shall bearranged with or provided with thefollowing:(A) A minimum of ten (10) feet (3,048 mm)

of clearance from the outlet to adjacentbuildings, property lines, and airintakes. Where space limitations abso-lutely prevent a ten (10) foot (3,048 mm)horizontal separation from an air intake,a vertical separation shall be permitted,with the exhaust outlet being aminimum of three (3) feet (914 mm)above any air intake located within ten(10) feet (3,048 mm) horizontally.

(B) The exhaust flow directed up and awayfrom the surface of the roof and aminimum of forty (40) inches (1,016mm) above the roof surface.


59

(C) The ability to drain grease out of anytraps or low points formed in the fan orduct near the termination of the systeminto a collection container that isnoncombustible, closed, rainproof, struc-turally sound for the service to which itis applied, and will not sustain combus-tion. A grease collection device that isapplied to exhaust systems shall notinhibit the performance of any fan.

Exception: Grease containers thatare evaluated for equivalency withthe preceding requirements andlisted as such.

(D) A listed grease duct complying withSection 510.4, or with ductworkcomplying with Section 510.5.

(E) A hinged upblast fan supplied with flex-ible weatherproof electrical cable andservice hold-open retainer to permitproper inspection and cleaning that islisted for commercial cooking equip-ment, provided the ductwork extends aminimum of eighteen (18) inches (457mm) above the roof surface and the fandischarges a minimum of forty (40)inches (1,016 mm) above the roof surface.(See Section 511.1.1.)

(F) Other approved fan, provided (1) itmeets the requirements of Sections510.8.2(C) and 511.1.3, and (2) itsdischarge or its extended duct dischargemeets the requirements of Section510.8.2(B).

510.8.2.2 Listed flexible connectors may beused on exterior roof locations when requiredfor proper equipment vibration isolation.510.8.2.3 Fans shall be provided with safeaccess and a work surface for inspection andcleaning. [NFPA 96:7.8.2.2]

510.8.3 Wall Terminations.510.8.3.1 Wall terminations shall bearranged with or provided with thefollowing properties:(A) Through a noncombustible wall with a

minimum of ten (10) feet (3,048 mm) ofclearance from the outlet to adjacentbuildings, property lines, grade level,combustible construction, or electricalequipment or lines, and the closest pointof any air intake or operable door orwindow at or below the plane of theexhaust termination. The closest pointof any air intake or operable door orwindow above the plane of the exhausttermination shall be a minimum of ten(10) feet (3,048 mm) distant, plus 0.25

feet (0.076m) for each one (1) degreefrom horizontal, the angle of degreebeing measured from the center of theexhaust termination to the center of theair intake or operable door or window.(See Figure 5-4.)

Exception: A wall termination in asecured area can be at a lowerheight above grade if acceptable tothe Authority Having Jurisdiction.

(B) The exhaust flow directed perpendicu-larly outward from the wall face orupward.

(C) All the ductwork pitched to drain thegrease back into the hood(s), or with adrain provided to bring the grease backinto a container within the building orinto a remote grease trap.

(D) A listed grease duct complying withSection 510.4, or other ducts complyingwith Section 510.5.

(E) An approved fan, provided it meets therequirements of Sections 510.8.3.1(C)and 511.1.1 or 511.1.3.

510.9 Solid-Fuel Duct Systems. Where solid-fuelcooking equipment is to be vented, the duct systemshall comply with Section 517.0.

511.0 Air Movement.511.1 Exhaust Fans for Commercial CookingEquipment.Where solid-fuel cooking equipment is to be vented,the duct system shall comply with Section 517.0.

511.1.1 Approved upblast fans with motorssurrounded by the airstream shall be hinged,supplied with flexible weatherproof electricalcable and service hold-open retainers, and listedfor this use. (See Figure 5-5.) Installation shallconform to the requirements of Section 510.8.511.1.2 In-Line Exhaust Fans.

511.1.2.1 In-line fans shall be of the typewith the motor located outside the airstreamand with belts and pulleys protected fromthe airstream by a grease-tight housing. Theyshall be connected to the exhaust duct byflanges securely bolted as shown in Figures5-6(a) – 5-6(d), or by a system specificallylisted for such use. Flexible connectors shallnot be used. [NFPA 96:8.1.2.1 – 8.1.2.3]511.1.2.2 If the design or positioning of thefan allows grease to be trapped, a draindirected to a readily accessible and visiblegrease receptacle, not exceeding one (1) gallon(3.8 L), shall be provided. In-line exhaust fansshall be located in an easily accessible area of


60

510.8 – 511.1

adequate size to allow for service or removal.If the duct system connected to the fan is in anenclosure, the space or room in which theexhaust fan is located shall have the same fireresistance rating as the enclosure. [NFPA96:8.1.2.4 – 8.1.2.6]

511.1.3 Utility set exhaust fans, if installed at therooftop termination point, shall meet the require-ments of Sections 510.8.2.1(A) and Section510.8.2.3. If the fan is installed within thebuilding, it shall be located in an easily accessiblearea of adequate size to allow for service orremoval. If the duct system connected to the fan isin an enclosure, the space or room in which theexhaust fan is located shall have the same fireresistance rating as the enclosure. The fan shall beconnected to the exhaust duct by flanges securelybolted as shown in Figures 5-6(a) through 5-6(d)or by a system specifically listed for such use.Flexible connectors shall not be used. Exhaustfans shall have a drain directed to a readily acces-sible and visible grease receptacle not to exceedone (1) gallon (3.8 L). [NFPA 96:8.1.3.1 - 8.1.3.6]511.1.4 Exhaust fan housings shall be constructedof carbon steel not less than 0.054 inch (1.37 mm)(No. 16 MSG) in thickness or stainless steel notless than 0.043 inch (1.09 mm) (No. 18 MSG) inthickness or, if listed, constructed in accordancewith the terms of the listing. [NFPA 96:8.1.4]511.1.5 Openings for cleaning, servicing, andinspection shall conform to the requirements ofSection 510.3.3. Clearances shall conform to therequirements of Sections 507.2, or 510.7.2.3 ifinstalled within an enclosure.511.1.6 All wiring and electrical equipment shallcomply with NFPA 70, National Electrical Code.

511.2 Airflow.511.2.1 The air velocity through any duct shallbe not less than 500 feet per minute (152.4 metersper minute). [NFPA 96:8.2.1.1]

Exception: Transition duct sections shall bepermitted to be connected to hoods andexhaust fans that do not meet this velocity,provided that they do not exceed three (3)feet (914 mm) in length and do not containtraps for grease.

511.2.2 Transition duct sections that do notexceed three (3) feet (914 mm) in length and donot contain grease traps shall be permitted to beconnected to hoods and exhaust fans that do notmeet this velocity. [NFPA 96:8.2.1.2]511.2.3 Exhaust-air volumes for hoods shall beof sufficient level to provide for capture andremoval of grease-laden cooking vapors. Testdata, performance acceptable to the AuthorityHaving Jurisdiction, or both, shall be provided,displayed, or both, upon request. [NFPA96:8.2.2.1, 8.2.2.2]

FIGURE 5-5 Upblast Fan Clearances. [NFPA96:7.8.2.1]

EXHAUST SYSTEMS Figure 5-4 – 511.2

61

FIGURE 5-4 Exhaust Termination Distance fromFresh Air Intake (FAI) or Operable Door or Window.[NFPA 96:7.8.3]

Exception: Lower exhaust-air volumes shallbe permitted during no-load cooking condi-tions, provided they are sufficient to captureand remove flue gases and residual vaporsfrom cooking equipment.

511.2.4 A hood exhaust fan(s) shall continue tooperate after the extinguishing system has beenactivated, unless fan shutdown is required by alisted component of the ventilation system or bythe design of the extinguishing system. It shallnot be required to restart the hood exhaust fanwhen the extinguishing system is activated if theexhaust fan and all cooking equipment servedby the fan had previously been shut down. Thehood exhaust fan shall not be required to startupon activation of the extinguishing system ifthe exhaust fan and all cooking equipmentserved by the fan have previously been shutdown. [NFPA 96:8.2.3.1 - 8.2.3.2]

511.3 Replacement Air. Replacement air quantityshall be adequate to prevent negative pressures inthe commercial cooking area(s) from exceeding 0.02inch water column (4.98 kPa). When its fire-extin-guishing system discharges, makeup air suppliedinternally to a hood shall be shut off. [NFPA 96:8.3.1- 8.3.2]

Exception: Compensating hoods shall meet theairflow requirements specified in Sections508.4.1.3 through 508.4.1.5. Compensating hoodsshall extract at least 20 percent of their requiredexhaust airflow from the kitchen area.

511.4 Common Duct (Manifold) Systems.511.4.1 Master kitchen exhaust ducts that servemultiple tenants shall include provision to bleedair from outdoors or from adjacent spaces intothe master exhaust duct where required to main-

FIGURE 5-6(c) Typical Section of Duct-to-FanConnection–Sealant Method. [NFPA 96:8.1.2.2(c)]

FIGURE 5-6(b) Typical Section of Duct-to-FanConnection–Overlapping Method. [NFPA 96:8.1.2.2(b)]

FIGURE 5-6(d) Typical Section of Duct-to-FanConnection–Direct to Fan Inlet Cone Method.[NFPA 96:8.1.2.2(d)]


62

Figure 5-6(a) – 511.4

FIGURE 5-6(a) Typical Section of Duct-to-FanConnection–Butt Joint Method. [NFPA96:8.1.2.2(a)]

tain the necessary minimum air velocity in themaster exhaust duct. [NFPA 96:8.4.1]511.4.2 The bleed-air ducts shall connect to thetop or side of the master exhaust duct. [NFPA96:8.4.2]511.4.3 The bleed-air duct shall have a firedamper at least twelve (12) inches (305 mm) fromthe exhaust duct connection. [NFPA 96:8.4.3]511.4.4 The bleed-air duct shall have the sameconstruction and clearance requirements as themain exhaust duct from the connection to theexhaust duct to at least twelve (12) inches (305mm) on both sides of the fire damper. [NFPA96:8.4.4]511.4.5 Each bleed air duct shall have a meansof adjusting (e.g., using volume dampers) thebleed-air quantity. [NFPA 96:8.4.5]511.4.6 Such means to adjust the bleed air qualityshall be installed in between the fire damper andthe source of bleed air. [NFPA 96:8.4.6]511.4.7 A bleed air duct shall not be used for theexhaust of grease-laden vapors and shall be solabeled. [NFPA 96:8.4.7]511.4.8 Unused tenant exhaust connections tothe master exhaust duct that are not used asbleed air connections shall be disconnected andsealed at the main duct. [NFPA 96:8.4.8]

511.5 Solid-Fuel Air Movement Requirements.Where solid-fuel cooking equipment is used, exhaustand replacement air also shall comply with Section517.0.

512.0 Auxiliary Equipment.512.1 Dampers. Dampers shall not be installed inexhaust ducts or exhaust duct systems. [NFPA96:9.1.1]

512.1.1 Where specifically listed for such use orwhere required as part of a listed device orsystem, dampers in exhaust ducts or exhaustduct systems shall be permitted. [NFPA 96:9.1.2]

512.2 Electrical Equipment.512.2.1 Wiring systems of any type shall not beinstalled in ducts. [NFPA 96:9.2.1]512.2.2 Only where specifically listed for suchuse shall motors, lights, and other electricaldevices be permitted to be installed in ducts orhoods or located in the path of travel of exhaustproducts. [NFPA 96:9.2.2]512.2.3 Lighting units on hoods shall not belocated in concealed spaces.512.2.4 Lighting units shall be permitted inconcealed spaces where such units are part of alisted exhaust hood. [NFPA 96:9.2.3.3]

512.2.5 Listed lighting units specifically listedfor such use and installed in accordance with theterms of the listing shall be permitted to beinstalled in concealed spaces. [NFPA 96:9.2.3.4]512.2.6 All electrical equipment shall beinstalled in accordance with NFPA 70, NationalElectrical Code, with due regard to the effects ofheat, vapor, and grease on the equipment.

512.3 Other Equipment.512.3.1 Fume incinerators, thermal recoveryunits, air pollution control devices, or otherdevices shall be permitted to be installed inducts or hoods or located in the path of travel ofexhaust products where specifically approvedfor such use. Downgrading other parts of theexhaust system due to the installation of theseapproved devices, whether listed or not, shallnot be allowed. [NFPA 96:9.3.1 - 9.3.2]512.3.2 Any equipment, listed or otherwise, thatprovides secondary filtration or air pollutioncontrol and that is installed in the path of travelof exhaust products shall be provided with anapproved automatic fire-extinguishing systemfor the protection of the component sections ofthe equipment and shall include protection ofthe ductwork downstream of the equipment,whether or not the equipment is provided with adamper. Filter media used in secondary filtra-tion or air pollution control units and notcomplying with Section 509.2.4 shall have fireprotection that is adequate for the filter mediabeing used in accordance with the fire-extin-guishing system manufacturer’s instructions. Ifthe equipment can be a source of ignition, it shallbe provided with appropriate detection tooperate the fire-extinguishing system. [NFPA96:9.3.3, 9.3.3.1, 9.3.4]512.3.3 Where a cooking exhaust systememploys an air pollution control device thatrecirculates air into the building, the provisionsof Section 516.0 shall apply. [NFPA 96:9.3.5]

512.4 Solid-Fuel Auxiliary Equipment. Where solidfuel cooking comprises any part of a cooking opera-tion, additional provisions and equipment asdescribed in Section 517.0 shall be used whererequired.

513.0 Fire-Extinguishing Equipment.513.1 General Requirements.

513.1.1 Fire-extinguishing equipment for theprotection of grease removal devices, hoodexhaust plenums, and exhaust duct systemsshall be provided. [NFPA 96:10.1.1]


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513.1.2 Cooking equipment that producesgrease-laden vapors (such as, but not limited to,deep-fat fryers, ranges, griddles, broilers, woks,tilting skillets, and braising pans) shall beprotected by fire-extinguishing equipment.[NFPA 96:10.1.2]

513.2 Types of Equipment.513.2.1 Fire-extinguishing equipment shallinclude both automatic fire-extinguishingsystems as primary protection and portable fireextinguishers as secondary backup. [NFPA96:10.2.1]

513.2.1.1 A placard identifying the use ofthe extinguisher as secondary backup meansto the automatic fire suppression systemshall be conspicuously placed near eachportable fire extinguisher in the cookingarea. [NFPA 96:10.2.2]

513.2.2 Automatic fire-extinguishing systemsshall comply with standard UL 300, Fire Testingof Fire Extinguishing Systems for Protection ofRestaurant Cooking Areas, or other equivalentstandards and shall be installed in accordancewith their listings. [NFPA 96:10.2.3]

Exception: Automatic fire-extinguishingequipment provided as part of listed recir-culating systems complying with standardUL 710B, Outline of Investigation for Recircu-lating Exhaust System.513.2.2.1 Automatic fire-extinguishingsystems shall be installed in accordance withthe terms of their listing, the manufacturer’sinstructions, and the following standardswhere applicable. [NFPA 96:10.2.6](1) NFPA 12, Standard on Carbon Dioxide

Extinguishing Systems(2) NFPA 13, Standard for the Installation of

Sprinkler Systems(3) NFPA 17, Standard for Dry Chemical

Extinguishing Systems(4) NFPA 17A, Standard for Wet Chemical

Extinguishing Systems513.2.3 In existing systems, when changes in thecooking media, positioning, or replacement ofcooking equipment occur, the fire-extinguishingsystem shall be made to comply with 513.2.2.[NFPA 96:10.2.3.1]513.2.4 Modification of Existing HoodSystems.

513.2.4.1 Any abandoned pipe or conduitfrom a previous installation shall beremoved from within the hood, plenum,and exhaust duct. [NFPA 96:10.2.7.1]

513.2.4.2 Penetrations and holes resultingfrom the removal of conduit or piping shallbe sealed with listed or equivalent liquidtight sealing devices. [NFPA 96:10.2.7.2]513.2.4.3 The addition of obstructions tospray patterns from the cooking appliancenozzle(s) such as baffle plates, shelves, orany modification shall not be permitted.[NFPA 96:10.2.7.3]513.2.4.4 Changes or modifications to thehazard after installation of the fire extin-guishing systems shall result in reevaluationof the system design by a properly trained,qualified, and certified person(s). [NFPA96:10.2.7.4]

513.2.5 Fixed Baffle Hoods with Water Wash.Grease removal devices, hood exhaust plenums,and exhaust ducts requiring protection in accor-dance with Section 513.1.1 shall be permitted tobe protected by a listed fixed baffle hoodcontaining a constant or fire-actuated waterwash system that is listed and in compliancewith UL 300 or other equivalent standards andshall be installed in accordance with the require-ments of their listing. [NFPA 96:10.2.8.1]

513.2.5.1 The water for listed, fixed bafflehood assemblies shall be permitted to besupplied from the domestic water supplywhen the minimum water pressure andflow are provided in accordance with theterms of the listing. [NFPA 96:10.2.8.3]513.2.5.2 The water supply shall becontrolled by a supervised water supplycontrol valve. [NFPA 96:10.2.8.4]513.2.5.3 The water wash in the fixed bafflehood shall be activated by the cookingequipment extinguishing system. [NFPA96:10.2.8.5]513.2.5.4 A water-wash system approved tobe used for protection of the grease removaldevice(s), hood exhaust plenum(s), exhaustduct(s), or combination thereof shall includeinstruction and appropriate electrical inter-face for simultaneous activation of thewater-wash system from an automatic fire-extinguishing system, where the automaticfire-extinguishing system is used forcooking equipment protection only. [NFPA96:10.2.8.6]513.2.5.5 Where the fire-extinguishingsystem provides protection for the cookingequipment, hood, and duct, activation of thewater wash shall not be required. [NFPA96:10.2.8.7]


64

513.1 – 513.2

513.2.5.6 The water required for listed auto-matic fire-extinguishing systems shall bepermitted to be supplied from the domesticwater supply where the minimum waterpressure and flow are provided in accor-dance with the terms of the listing. Thewater supply shall be controlled by a super-vised water supply control valve. [NFPA96:10.2.9]

513.2.6 Water Valve Supervision. Valvescontrolling the water supply to listed fixed bafflehood assemblies, automatic fire-extinguishingsystems, or both shall be listed indicating type ofvalve and shall be supervised open by one of thefollowing methods:(1) Central station, proprietary, or remote

station alarm service(2) Local alarm service that will cause the

sounding of an audible signal at a constantlyattended point

(3) Locking valves open(4) Sealing of valves and approved weekly

recorded inspection. [NFPA 96:10.2.10]513.3 Simultaneous Operation. Fixed-pipe extin-guishing systems in a single hazard area shall bearranged for simultaneous automatic operation uponactuation of anyone of the systems. [NFPA 96:10.3.1]

513.3.1 Simultaneous operation shall not berequired where the fixed pipe extinguishingsystem is an automatic sprinkler system. [NFPA96:10.3.2]513.3.2 Simultaneous operation shall not berequired where dry or wet chemical system shallbe permitted to be used to protect commonexhaust ductwork by one of the methods speci-fied in NFPA 17 or NFPA 17A. [NFPA 96:10.3.3]

513.4 Fuel Shutoff.513.4.1 Upon activation of any fire-extin-guishing system for a cooking operation, allsources of fuel and electric power that produceheat to all equipment requiring protection bythat system shall automatically shut off. [NFPA96:10.4.1]

Exception: Solid-fuel cooking operations.513.4.2 Steam supplied from an external sourceshall not be required to automatically shut off.[NFPA 96:10.4.2]513.4.3 Any gas appliance not requiring protec-tion, but located under the same ventilatingequipment, shall also automatically shut offupon activation of any extinguishing system.[NFPA 96:10.4.3]

513.4.4 Shutoff devices shall require manualreset. [NFPA 96:10.4.4]

513.5 Manual Activation.513.5.1 A readily accessible means for manualactivation shall be located between forty-two(42) inches and forty-eight (48) inches (1,067 mmand 1,219 mm) above the floor, located in a pathof exit or egress, and clearly identify the hazardprotected. A manual actuation device shall belocated a minimum of ten (10) feet (3 m) whenpossible and a maximum of twenty (20) feet (6m) from the protected kitchen appliance(s)within the path of egress. Manual actuationusing a cable-operated pull station shall notrequire more than forty (40) pounds (178 N) offorce, with a pull movement not to exceed four-teen (14) inches (356 mm) to actuate the firesuppression system. The automatic and manualmeans of system activation external to thecontrol head or releasing device shall be separateand independent of each other so that failure ofone will not impair the operation of the other.[NFPA 96:10.5.1 – 10.5.2]513.5.2 The manual means of system activationshall be permitted to be common with the auto-matic means if the manual activation device islocated between the control head or releasingdevice and the first fusible link. [NFPA 96:10.5.3]513.5.3 An automatic sprinkler system shall notrequire a manual means of system activation.[NFPA 96:10.5.4]513.5.4 The means for manual actuator(s) shallbe mechanical or rely on electrical power foractuation. [NFPA 96:10.5.5]513.5.5 Electrical power shall be permitted to beused for manual activation if a standby powersupply is provided or if supervision is providedin accordance with Section 513.7. [NFPA96:10.5.6]

513.6 System Annunciation.513.6.1 Upon activation of an automatic fireextinguishing system, an audible alarm or visualindicator shall be provided to show that thesystem has activated. [NFPA 96:10.6.1]513.6.2 Where a fire alarm signaling system isserving the occupancy where the extinguishingsystem is located, the activation of the automaticfire-extinguishing system shall activate the firealarm signaling system. [NFPA 96:10.6.2]

513.7 System Supervision.513.7.1 Where electrical power is required tooperate the automatic fire-extinguishing system,it shall be monitored by a supervisory alarm,with a standby power supply provided. [NFPA96:10.7.1]


65

513.7.2 System supervision shall not be requiredwhere an automatic fire-extinguishing system(s)includes automatic mechanical detection andactuation as a backup detection system.[NFPA 96:10.7.2]513.7.3 System supervision shall not be requiredwhere a fire-extinguishing system(s) is intercon-nected or interlocked with the cooking equip-ment power source(s) so that if the fire extin-guishing system becomes inoperable due topower failure, all sources of fuel or electricpower that produce heat to all cooking equip-ment serviced by that hood shall automaticallyshut off. [NFPA 96:10.7.3]513.7.4 System supervision shall not be requiredwhere an automatic fire-extinguishing system,including automatic mechanical detection andactuation, is electrically connected to a listed fire-actuated water-wash system for simultaneousoperation of both systems. [NFPA 96:10.7.4]

513.8 Special Design and Application.513.8.1 Hoods containing automatic fire extin-guishing systems are protected areas; therefore,these hoods are not considered obstructions tooverhead sprinkler systems and shall not requirefloor coverage underneath. [NFPA 96:10.8.1]513.8.2 A single listed detection device, listedwith the extinguishing system, shall bepermitted for more than one (1) appliance wheninstalled in accordance with the terms of thelisting. [NFPA 96:10.8.2]

513.9 Review and Certification.513.9.1 Where required, complete drawings ofthe system installation, including the hood(s),exhaust duct(s), and appliances, along with theinterface of the fire-extinguishing system detec-tors, piping, nozzles, fuel shutoff devices, agentstorage container(s), and manual actuationdevice(s), shall be submitted to the AuthorityHaving Jurisdiction. [NFPA 96:10.9.1]

513.10 Installation Requirements.513.10.1 Installation of systems shall beperformed only by persons properly trained andqualified to install the specific system beingprovided. The installer shall provide certificationthat the installation is in agreement with theterms of the listing and the manufacturer'sinstructions and/or approved design. [NFPA96:10.9.2]

513.11 Portable Fire Extinguishers.513.11.1 Portable fire extinguishers shall beinstalled in kitchen cooking areas in accordancewith NFPA 10, Standard for Portable Fire extin-guishers. Such extinguishers shall use agents thatspecify upon contact with hot grease, such as

sodium bicarbonate and potassium bicarbonatedry chemical and potassium carbonate solutions.Class B gas-type portables such as CO2 andhalon shall not be permitted in kitchen cookingareas. Manufacturer's recommendations shall befollowed. [NFPA 96:10.10.1 – 10.10.4]

513.11.1.1 Portable fire extinguishers listedspecifically for use in the kitchen cookingareas shall also be permitted.

513.11.2 Other fire extinguishers in the kitchenarea shall be installed in accordance with NFPA10, Standard for Portable Fire Extinguishers. [NFPA96:10.10.5]

513.12 Solid-Fuel Fire-Extinguishing Equipment.Where solid-fuel cooking equipment is served by fireextinguishing equipment, the provisions of Section517.0 shall apply.

514.0 Procedures for the Use and Maintenance ofEquipment.514.1 Operating Procedures.

514.1.1 Exhaust systems shall be operatedwhenever cooking equipment is turned on.[NFPA 96:11.1.1]514.1.2 Filter-equipped exhaust systems shall notbe operated with filters removed. [NFPA 96:11.1.2]514.1.3 Openings provided for replacing airexhausted through ventilating equipment shallnot be restricted by covers, dampers, or anyother means that would reduce the operatingefficiency of the exhaust system. [NFPA96:11.1.3]514.1.4 Instructions for manually operating thefire-extinguishing system shall be postedconspicuously in the kitchen and shall bereviewed periodically with employees by themanagement. [NFPA 96:11.1.4]514.1.5 Listed exhaust hoods shall be operatedin accordance with the terms of their listings andthe manufacturer's instructions. [NFPA96:11.1.5]514.1.6 Cooking equipment shall not be oper-ated while its fire-extinguishing system orexhaust system is nonoperational or otherwiseimpaired. [NFPA 96:11.1.6]514.1.7 Secondary filtration and pollutioncontrol equipment shall be operated in accor-dance with the terms of its listing and the manu-facturer's recommendations. [NFPA 96:11.1.7]514.1.8 Inspection and maintenance of equip-ment allowed in Section 512.3.1 shall beconducted by properly trained and qualifiedpersons at a frequency determined by the manu-


66

513.7 – 514.1

facturer's instructions or equipment listing.[NFPA 96:11.1.8]

514.2 Inspection. Maintenance of the fire-extin-guishing systems and listed exhaust hoodscontaining a constant or fire-activated water systemthat is listed to extinguish a fire in the greaseremoval devices, hood exhaust plenums, andexhaust ducts shall be made by properly trained,qualified, and certified person(s) or company accept-able to the Authority Having Jurisdiction at leastevery six (6) months. [NFPA 96:11.2.1]

514.2.1 All actuation components, includingremote manual pull stations, mechanical or elec-trical devices, detectors, actuators, and fire-actu-ated dampers, shall be checked for proper opera-tion during the inspection in accordance withthe manufacturer's listed procedures. In additionto these requirements, the specific inspectionrequirements of the applicable NFPA standardshall also be followed. [NFPA 96-04:11.2.2 -11.2.3]514.2.2 Fusible links (including fusible links onfire damper assemblies) and automatic sprinklerheads shall be replaced at least semiannually, ormore frequently if necessary where required bythe manufacturer. [NFPA 96-04:11.2.4]514.2.3 The year of manufacture and the date ofinstallation of the fusible links shall be markedon the system inspection tag. The tag shall besigned or initialed by the installer. [NFPA96:11.2.5]

Other detection devices not includingfusible links and automatic sprinklers shall beserviced or replaced in accordance with themanufacturer’s recommendations. [NFPA 96-04:11.2.6]514.2.4Where automatic bulb-type sprinklers orspray nozzles are used and annual examinationshows no buildup of grease or other material onthe sprinkler or spray nozzles, annual replace-ment shall not be required. [NFPA 96:11.2.7]514.2.5 If required, certificates of inspection andmaintenance shall be forwarded to the AuthorityHaving Jurisdiction. [NFPA 96:11.2.8]

514.3 Inspection for Grease Buildup.514.3.1 The entire exhaust system shall beinspected for grease buildup by a properlytrained, qualified, and certified company orperson(s) acceptable to the Authority HavingJurisdiction in accordance with Table 5-4.

514.4 Cleaning of Exhaust Systems.514.4.1 Upon inspection, if the exhaust system isfound to be contaminated with deposits from

grease-laden vapors, the contaminated portionsof the exhaust system shall be cleaned by a prop-erly trained, qualified, and certified company orperson(s) acceptable to the Authority HavingJurisdiction. [NFPA 96:11.6.1]514.4.2 Hoods, grease removal devices, fans,ducts, and other appurtenances shall be cleanedto remove combustible contaminant's prior tosurfaces becoming heavily contaminated withgrease or oily sludge. [NFPA 96:11.6.2]514.4.3 At the start of the cleaning process, elec-trical switches that could be activated acciden-tally shall be locked out. [NFPA 96:11.6.3]514.4.4 Components of the fire suppressionsystem shall not be rendered inoperable duringthe cleaning process. [NFPA 96:11.6.4]514.4.5 Fire-extinguishing systems shall bepermitted to be rendered inoperable during thecleaning process where serviced by properlytrained and qualified persons. [NFPA 96:11.6.5]514.4.6 Flammable solvents or other flammablecleaning aids shall not be used. [NFPA 96:11.6.6]514.4.7 Cleaning chemicals shall not be appliedon fusible links or other detection devices of theautomatic extinguishing system. [NFPA 96:11.6.7]514.4.8 After the exhaust system is cleaned, itshall not be coated with powder or othersubstance. [NFPA 96:11.6.8]514.4.9 When cleaning procedures arecompleted, all access panels (doors) and coverplates shall be restored to their normal opera-tional condition. [NFPA 96:11.6.9]514.4.10 When an access panel is removed, aservice company label or tag preprinted with thename of the company and giving the date ofinspection or cleaning shall be affixed near theaffected access panels. [NFPA 96:11.6.10]


67

TABLE 5-4Exhaust System Inspection Schedule

[NFPA 96: Table 11.4]Type or Volume of CookingFrequency

Frequency

Systems serving solid-fuel cookingoperations

Monthly

Systems serving high-volume cookingoperations such as 24-hour cooking,charbroiling, or wok cooking

Quarterly

Systems serving moderate-volumecooking operations

Semi-annually

Systems serving low-volume cookingoperations, such as churches, daycamps, seasonal businesses, or seniorcenters.

Annually

514.4.11 Dampers and diffusers shall be posi-tioned for proper airflow. [NFPA 96:11.6.11]514.4.12 When cleaning procedures arecompleted, all electrical switches and systemcomponents shall be returned to an operablestate. [NFPA 96:11.6.12]514.4.13 When an exhaust cleaning service isused, a certificate showing the name of theservicing company, the name of the personperforming the work, and the date of inspectionor cleaning shall be maintained on the premises.[NFPA 96:11.6.13]514.4.14 After cleaning or inspection iscompleted, the exhaust cleaning company andthe person performing the work at the locationshall provide the owner of the system with awritten report that also specifies areas that wereinaccessible or not cleaned. [NFPA 96:11.6.14]514.4.15 Where required, certificates of inspec-tion and cleaning and reports of areas notcleaned shall be submitted to the AuthorityHaving Jurisdiction. [NFPA 96:11.6.15]

515.0 Minimum Safety Requirements for CookingEquipment.515.1 Cooking Equipment.

515.1.1 Cooking equipment shall be approvedbased on one of the following criteria:(A) Listings by a testing laboratory.(B) Test data acceptable to the Authority

Having Jurisdiction. [NFPA 96:12.1.1]515.1.2 Installation.

515.1.2.1 All listed appliances shall beinstalled in accordance with the terms oftheir listings and the manufacturer's instruc-tions. [NFPA 96:12.1.2.1]515.1.2.2 Cooking appliances requiringprotection shall not be moved, modified, orrearranged without prior reevaluation of thefire-extinguishing system by the systeminstaller or servicing agent, unless otherwiseallowed by the design of the fire-extin-guishing system. [NFPA 96:12.1.2.2]

515.1.2.3 The fire-extinguishing systemshall not require re-evaluation wherethe cooking appliances are moved toperform maintenance and cleaningprovided the appliances are returned toapproved design location prior tocooking operations, and any discon-nected fire-extinguishing systemnozzles attached to the appliances are

reconnected in accordance with themanufacturer’s listed design manual.[NFPA 96:12.1.2.3]

515.1.2.4 All deep-fat fryers shall beinstalled with at least a sixteen (16) inch (406mm) space between the fryer and surfaceflames from adjacent cooking equipment.[NFPA 96:12.1.2.4]515.1.2.5 Where a steel or tempered glassbaffle plate is installed at a minimum eight(8) inches (203 mm) in height between thefryer and surface flames of the adjacentappliance, the requirement for a sixteen (16)inch (406 mm) space shall not apply. [NFPA96:12.1.2.5]515.1.2.6 If the fryer and the surface flamesare at different horizontal planes, theminimum height of eight (8) inches (203mm) shall be measured from the higher ofthe two. [NFPA 96:12.1.2.5.1]

515.2 Operating Controls. Deep-fat fryers shall beequipped with a separate high-limit control in addi-tion to the adjustable operating control (thermostat)to shut off fuel or energy when the fat temperaturereaches 475°F (246°C) at one (1) inch (25 mm) belowthe surface. [NFPA 96:12.2]515.3 Cooking Equipment Maintenance.

515.3.1 An inspection and servicing of thecooking equipment shall be made at least annu-ally by properly trained and qualified persons.[NFPA 96:11.5.1]515.3.2 Cooking equipment that collects greasebelow the surface, behind the equipment, or incooking equipment flue gas exhaust, such asgriddles or charbroilers, shall be inspected and,if found with grease accumulation, cleaned by aproperly trained, qualified, and certified personacceptable to the authority having jurisdiction.[NFPA 96:11.5.2]

516.0 Recirculating Systems.516.1 General Requirements. Recirculatingsystems containing or for use with appliances usedin processes producing smoke or grease-ladenvapors shall be equipped with componentscomplying with the following:(A) The clearance requirements of Section 507.2.(B) A hood complying with the requirements of

Section 508.0.(C) Grease removal devices complying with Section

509.0.(D) The air movement requirements of Sections

511.2.1 and 511.2.2.


68

514.4 – 516.1

(E) Auxiliary equipment (such as particulate andodor removal devices) complying with Section512.0.

(F) Fire-extinguishing equipment complying withthe requirements of Section 513.0.

Exception: References to ducts in Sections513.1.1 and 513.5.1.

(G) The use and maintenance requirements of 514.0.(H) The minimum safety requirements of Section

515.0.(I) All the requirements of this chapter. [NFPA

96:13.1]516.2 Design Restrictions. All recirculating systemsshall comply with Section 516.2. [NFPA 96:13.2]

516.2.1 Only gas- or electrically fueled cookingappliances shall be used. Gas-fueled appliancesshall not have the combustion flue outlet(s)directly connected to the recirculating system.Gas-fueled appliances shall have a minimumeighteen (18) inch (457 mm) clearance from theflue outlet to the filter inlet in accordance withSection 509.2.3 and shall meet the installationrequirements of NFPA 54, National Fuel Gas Code,or NFPA 58, Liquefied Petroleum Gas Code. [NFPA96:13.2.1 – 13.2.3]516.2.2 Recirculating systems shall be listedwith a testing laboratory. The recirculatingsystem listing shall include integral fire protec-tion for recirculating hoods, including canopytype [NFPA 96:13.2.4.1]516.2.3 Cooking appliances that require protec-tion and that are under a recirculating hood shallbe protected by either the integral fire protectionsystem for the hood or a system in accordancewith Section 513.0. [NFPA 96:13.2.4.2]516.2.4 A recirculating system shall not usecooking equipment that exceeds that recircu-lating system's labeled maximum limits for thattype of equipment, stated in maximum energyinput, maximum cooking temperature, andmaximum square area of cooking surface orcubic volume of cooking cavity. [NFPA96:13.2.6]516.2.5 The listing label shall show the type(s)of cooking equipment tested and the maximumlimits specified in 516.2.4. [NFPA 96:13.2.7]516.2.6 A fire-actuated damper shall be installedat the exhaust outlet of the system. The actua-tion device shall have a maximum temperaturerating of 375°F (190°C). [NFPA 96:13.2.8, 13.2.10]516.2.7 No electrical wiring shall be installed inthe interior sections of the hood plenum thatmight become exposed to grease.

Exception: As permitted by NFPA 70,National Electrical Code.

516.2.8 The power supply of any electrostaticprecipitator (ESP) shall be of the "cold spark,"ferro-resonant type in that the voltage falls off asthe current draw of a short increases. [NFPA96:13.2.11]516.2.9 Listing evaluation shall include thefollowing:(A) Capture and containment of vapors at

published and labeled airflows.(B) Grease discharge at the exhaust outlet of the

system not to exceed an average of 5 mg/m3

of exhausted air sampled from that equip-ment at maximum amount of product that iscapable of being processed over a contin-uous eight (8) hour test per EPA TestMethod 202, Determination of CondensableParticulate Emissions for Stationary Sources,with the system operating at its minimumlisted airflow.

(C) Listing and labeling of clearance tocombustibles from all sides, top, and bottom.

(D) Electrical connection in the field in accor-dance with NFPA 70, National Electrical Code.

(E) Interlocks on all removable components thatlie in the path of airflow within the unit toensure that they are in place during opera-tion of the cooking appliance. [NFPA96:13.2.12]

516.3 Interlocks. The recirculating system shall beprovided with interlocks of all critical componentsand operations as indicated in Sections 516.3.1through 516.3.4 such that, if any of these interlocksare interrupted, the cooking appliance shall not beable to operate. [NFPA 96:13.3.1]

516.3.1 All closure panels encompassing airflowsections shall have interlocks to ensure thepanels are in place and fully sealed.[NFPA96:13.3.2]516.3.2 Each filter component (grease and odor)shall have an interlock to prove the componentis in place. [NFPA 96:13.3.3]516.3.3 ESP Interlocks.

516.3.3.1 Each ESP shall have a sensor toprove its performance is as designed, withno interruption of the power to exceed two(2) minutes. [NFPA 96:13.3.4.1]516.3.3.2 The sensor shall be a manual resetdevice or circuit. [NFPA 96:13.3.4.2]

516.3.4 An airflow switch or transducer shall beprovided after the last filter component toensure that a minimum airflow is maintained.This device opens the interlock circuit when theairflow falls twenty-five (25) percent below the


69

516.3 – 517.3

70


system's normal operating flow or ten (10)percent below its listed minimum rating,whichever is lower. This switch or transducershall be a manual reset device or circuit. [NFPA96:13.3.5]

516.4 Location and Application Restrictions. Thelocation of recirculating systems shall be approvedby the Authority Having Jurisdiction. Items to bereviewed in the fire risk assessment shall include,but not be limited to, life safety, combustibility ofsurroundings, proximity to air vents, and total fuelload. [NFPA 96:13.4]516.5 Additional Fire Safety Requirements.

516.5.1 In addition to the appliance nozzle(s), arecirculating system shall be listed with theappropriate fire protection for grease filters,grease filtration, odor filtration units, and duct-work where applicable. [NFPA 96:13.5.1]516.5.2 In addition to any other fire-extin-guishing system actuation device, there shall bea fire-extinguishing system actuation deviceinstalled downstream of any ESP.[NFPA96:13.5.2]516.5.3 The requirements of Section 513.6 shallalso apply to recirculating system locations.[NFPA 96:13.5.3]

516.6 Use and Maintenance.516.6.1 Automatic or manual covers on cookingappliances, especially fryers, shall not interferewith the application of the fire suppressionsystem.[NFPA 96:13.6.1]516.6.2 All filters shall be cleaned or replaced inaccordance with the manufacturer's instructions.[NFPA 96:13.6.2]516.6.3 All ESPs shall be cleaned a minimum ofonce per week following manufacturer'scleaning instructions. [NFPA 96:13.6.3]516.6.4 The entire hood plenum and the blowersection shall be cleaned a minimum of onceevery three (3) months. [NFPA 96:13.6.4]516.6.5 Inspection and testing of the total opera-tion and all safety interlocks in accordance withthe manufacturer's instructions shall beperformed by qualified service personnel aminimum of once every six (6) months, or morefrequently if required. [NFPA 96:13.6.5]516.6.6 Fire-extinguishing equipment shall beinspected in accordance with Section 514.2.[NFPA 96:13.6.6]516.6.7 A signed and dated log of maintenanceas performed in accordance with Sections 516.6.4and 516.6.5 shall be available on the premises foruse by the Authority Having Jurisdiction.[NFPA 96:13.6.7]

517.0 Solid-Fuel Cooking Operations.517.1 Venting Application. Venting requirements ofsolid-fuel cooking operations shall be determined inaccordance with Sections 517.1.1 through 517.1.6.

517.1.1 Where solid-fuel cooking equipment isrequired by the manufacturer to have a naturaldraft, the vent shall comply with Section 517.4.517.1.2 Where the solid-fuel cooking equipmenthas a self-contained top, is the only appliance tobe vented in an isolated space (except for a singlewater heater with its own separate vent), has aseparate makeup-air system, and is providedwith supply and return air (not supplied orreturned from other spaces), the system shallcomply with Sections 517.4 and 517.6.517.1.3 Where the solid-fuel cooking equipmentis located in a space with other vented equip-ment, all vented equipment shall have anexhaust system interlocked with a makeup-airsystem for the space as per Section 517.6.517.1.4 Natural draft ventilation systems andpower-exhausted ventilation systems shallcomply with Sections 517.3, 517.4, and 517.6.517.1.5 Where a solid-fuel cooking applianceallows effluent to escape from the applianceopening, this opening shall be covered by a hoodand an exhaust system that meets the require-ments of Sections 517.3, 517.4, and 517.6.517.1.6 Solid-fuel cooking operations shall havespark arresters to minimize the passage ofairborne sparks and embers into plenums andducts. Where the solid-fuel cooking operation isnot located under a hood, a spark arrester shallbe provided to minimize the passage of sparksand embers into flues and chimneys.

517.2 Location of Appliances.517.2.1 Every appliance shall be located withrespect to building construction and other equip-ment so as to permit access to the appliance.517.2.2 Solid-fuel cooking appliances shall notbe installed in confined spaces.

Exception: Solid-fuel cooking appliances listedfor installation in confined spaces shall beinstalled in accordance with the terms of thelisting and the manufacturer's instructions.

517.2.3 Solid-fuel cooking appliances shall notbe installed in any location where gasoline orany other flammable vapors or gases are likelyto be present.

517.3 Hoods for Solid-Fuel Cooking.517.3.1 Hoods shall be sized and located in amanner capable of capturing and containing allof the effluent discharging from the appliances.

71

517.3 – 517.7EXHAUST SYSTEMS

The hood and its exhaust system shall complywith the provisions of the code.517.3.2 All solid-fuel cooking equipment servedby hood and duct systems shall be separate fromall other exhaust systems.

Exception: Cooking equipment notrequiring automatic fire-extinguishingequipment (as per the provisions of Section510.0) shall be permitted to be installedunder a common hood with solid-fuelcooking equipment that is served by a ductsystem separate from all other exhaustsystems.

517.4 Exhaust Systems for Solid-Fuel Cooking.Where a hood is not required, in buildings where theduct system is three (3) stories or less in height, aduct complying with Section 510.0 shall be provided.

517.4.1 If a hood is used, the duct system shallconform with the Section 510.0.517.4.2 A listed or approved grease duct systemshall be provided for solid-fuel cooking exhaustsystems that are four (4) stories in height orgreater.517.4.3 Where a hood is used, the duct systemshall conform with the requirements of Section510.0.517.4.4 Wall terminations of solid-fuel exhaustsystems shall be prohibited.

517.5 Grease Removal Devices for Solid-FuelCooking. Grease removal devices shall beconstructed of steel or stainless steel or be approvedfor solid-fuel cooking.

517.5.1 If airborne sparks and embers can begenerated by the solid-fuel cooking operation,spark arrester devices shall be used prior to thegrease removal device to minimize the entranceof these sparks and embers into the greaseremoval device and into the hood and ductsystem.517.5.2 Filters shall be a minimum of four (4)feet (1.2 m) above the appliance cooking surface.

517.6 Air Movement for Solid-Fuel Cooking.Exhaust system requirements shall comply with theprovisions of the code for hooded operation or shallbe installed in accordance with the manufacturer'srecommendation for unhooded applications.

517.6.1 A replacement or makeup-air systemshall be provided to ensure a positive supply ofreplacement air at all times during cooking oper-ations.517.6.2 Makeup-air systems serving solid-fuelcooking operations shall be interlocked with the

exhaust-air system and powered, if necessary, toprevent the space from attaining a negative pres-sure while the solid-fuel appliance is in opera-tion.

517.7 Fire-Extinguishing Equipment for Solid-Fuel Cooking.

517.7.1 Approved fire-extinguishing equipmentshall be provided to protect all solid-fuel-burning cooking appliances that might be asource of ignition of grease in the hood, greaseremoval device, or duct.

Exception: If acceptable to the AuthorityHaving Jurisdiction, solid-fuel-burningcooking appliances constructed of solidmasonry or reinforced portland or refractorycement concrete and vented in accordancewith NFPA 211, Standard for Chimneys, Fire-places, Vents, and Solid Fuel–BurningAppliances, Chapters 3 and 4, shall not requirefixed automatic fire-extinguishing equipment.

517.7.2 Approved fire-extinguishing equipmentshall be provided for the protection of greaseremoval devices, hoods, and duct systems.

Exception: If acceptable to the AuthorityHaving Jurisdiction, solid-fuel-burningcooking appliances constructed of solidmasonry or reinforced portland or refractorycement concrete and vented in accordancewith NFPA 211, Standard for Chimneys, Fire-places, Vents, and Solid Fuel–Burning Appli-ances, Chapters 3 and 4, shall not requireautomatic fire-extinguishing equipment.

517.7.3 Approved fire-extinguishing equipmentfor solid-fuel-burning cooking appliances, whererequired, shall comply with NFPA 211 and shallbe comprised of water-based agents.517.7.4 Fire-extinguishing equipment shall berated and designed to extinguish solid-fuelcooking fires, in accordance with the manufac-turer's recommendations. The fire-extinguishingequipment shall be of sufficient size to totallyextinguish fire in the entire hazard area andprevent reignition of the fuel.517.7.5 All solid-fuel appliances (whether or notunder a hood) with fireboxes of five (5) ft.3 (0.14m3) volume or less shall at least have a listed 2-Arated water-type fire extinguisher or a 1.6 gal (6L) wet chemical fire extinguisher listed for ClassK fires in accordance with NFPA 10, in theimmediate vicinity of the appliance. [NFPA96:14.7.8]517.7.6 Solid-fuel appliances with fireboxesexceeding five (5) ft.3 (0.14 m3) shall be providedwith a fixed-water-pipe system with a hose in

the immediate vicinity of the appliance. Thehose shall be equipped with an adjustable nozzlecapable of producing a fine to medium spray ormist. The nozzle shall be of the type that cannotproduce a straight stream. The system shall havea minimum operating pressure of forty (40) psi(275.8 kPa) and shall provide a minimum of five(5) gpm. [NFPA 96:14.7.9.1 – 14.7.9.2]517.7.7 Fire suppression for fuel storage areasshall comply with Section 517.9.517.7.8 In addition to the requirements ofSections 517.7.5 or 517.7.6, where any solid-fuelcooking appliance is also provided with auxil-iary electric, gas, oil, or other fuel for ignition orsupplemental heat and the appliance is alsoserved by any portion of a fire-extinguishingsystem complying with Section 513.0, such auxil-iary fuel shall be shut off upon actuation of thefire-extinguishing system.

517.8 Other Safety Requirements.517.8.1 Metal-fabricated solid-fuel cookingappliances shall be listed for the applicationwhere produced in practical quantities or shall beapproved by the Authority Having Jurisdiction.When listed, they shall be installed in accordancewith the terms of their listings and with theapplicable requirements of this standard.517.8.2 Site-built solid-fuel cooking appliancesshall be submitted for approval to the AuthorityHaving Jurisdiction before being considered forinstallation. All units shall be installed, operated,and maintained in accordance with theapproved terms of the manufacturer's instruc-tions and any additional requirements set forthby the Authority Having Jurisdiction.517.8.3 Except for the spark arrester required inSection 517.1.6, there shall be no additionaldevices of any type in any portion of the appli-ance, flue pipe, and chimney of a natural draftsolid-fuel operation.517.8.4 No solid-fuel cooking device of any typeshall be permitted for deep-fat frying involvingmore than one (1) quart of liquid shortening, norshall any solid-fuel cooking device be permittedwithin three (3) feet (0.92 m) of any deep-fatfrying unit.


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517.7 – 517.8

TABLE 5-5Minimum Sheet Metal Thickness for Round Ducts for Product-Conveying System DuctsReinf. Class 1

Negative SpacingPressure (Inches) Up to 7" 8" to 11" 12" to 15" 16" to 19" 20" to 23" 24" to 35" 36" to 47" 48" to 59" 60"

To 7" 0 .021 (24 ga.) .021 (24 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .127 (10 ga.)96 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.)48 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.)24 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.)

8" to 11" 0 .021 (24 ga.) .027 (22 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.)96 .021 (24 ga.) .027 (22 ga.) .027 (22 ga.) .044 (18 ga.) .044 (18 ga.) .044 (18 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.)48 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .033 (20 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.)24 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .027 (22 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.)


16" to 20" 0 .021 (24 ga.) .044 (18 ga.) .068 (14 ga.) .097 (12 ga.) .112 (11 ga.)96 .021 (24 ga.) .033 (20 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .112 (11 ga.) .112 (11 ga.) .112 (11 ga.)48 .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .112 (11 ga.)24 .021 (24 ga.) .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.)

Class 2To 7" 0 .027 (22 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .127 (10 ga.)

96 .027 (22 ga.) .027 (22 ga.) .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.)48 .027 (22 ga.) .027 (22 ga.) .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)24 .027 (22 ga.) .027 (22 ga.) .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)




Class 3

To 7" 0 .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .127 (10 ga.)96 .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.)48 .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.)24 .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.)


EXHAUST SYSTEMS Table 5-5

73

TABLE 5-5 (continued)Minimum Sheet Metal Thickness for Round Ducts for Product-Conveying System Ducts

Reinf. Class 3Negative SpacingPressure (Inches) Up to 7" 8" to 11" 12" to 15" 16" to 19" 20" to 23" 24" to 35" 36" to 47" 48" to 59" 60"12" to 15" 0 .033 (20 ga.) .033 (20 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.)



Class 4To 7" 0 .055 (16 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .127 (10 ga.)





Note: 1 in. = 25.4 mm

Longest Side of DuctClass 1 Class 2

Negative Reinf.Pressure Spacing Up to 12" 13" to 24" 25" to 36" 37" to 48" 49" to 60" Up to 12" 13" to 24" 25" to 36" 37" to 48" 49" to 60"

To 7" 48 .021 (24 ga.) .033 (20 ga.) .055 (16 ga.) .068 (14 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .068 (14 ga.)To 7" 24 .021 (24 ga.) .027 (22 ga.) .033 (20 ga.) .033 (20 ga.) .033 (20 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)To 7" 12 .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .021 (24 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)

8" to 11" 48 .027 (22 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .033 (20 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.)8" to 11" 24 .027 (22 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .033 (20 ga.) .055 (16 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.)8" to 11" 12 .021 (24 ga.) .027 (22 ga.) .027 (22 ga.) .027 (22 ga.) .027 (22 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)

12" to 15" 48 .044 (18 ga.) .097 (12 ga.) .044 (18 ga.) .044 (18 ga.)12" to 15" 24 .044 (18 ga.) .055 (16 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.) .044 (18 ga.) .044 (18 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)12" to 15" 12 .027 (22 ga.) .044 (18 ga.) .044 (18 ga.) .044 (18 ga.) .044 (18 ga.) .033 (20 ga.) .044 (18 ga.) .055 (16 ga.) .055 (16 ga.) .055 (16 ga.)


Class 3 Class 4To 7" 48 .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.)To 7" 24 .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)To 7" 12 .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)

8" to 11" 48 .044 (18 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.)8" to 11" 24 .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)8" to 11" 12 .044 (18 ga.) .055 (16 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)


16" to 20" 48 .068 (14 ga.) .112 (11 ga.) .055 (16 ga.) .112 (11 ga.)16" to 20" 24 .068 (14 ga.) .068 (14 ga.) .112 (11 ga.) .112 (11 ga.) .112 (11 ga.) .055 (16 ga.) .068 (14 ga.) .112 (11 ga.) .112 (11 ga.) .112 (11 ga.)16" to 20" 12 .044 (18 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .068 (14 ga.) .055 (16 ga.) .068 (14 ga.) .097 (12 ga.) .097 (12 ga.) .097 (12 ga.)Note: 1 in. = 25.4 mm


74

Table 5-5 continued – Table 5-6

TABLE 5-6Minimum Sheet Metal Thickness for Rectangular Ducts

Uniform Mechanical Code- 2009 Chapter 5

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Transcript of Uniform Mechanical Code- 2009 Chapter 5