SMoke Alarm Detection Technology

8/10/2019 SMoke Alarm Detection Technology

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Smoke Alarm Detection

Technology(Prepared for CALFIRE 3-28-11)


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AgendaWhat is required or recommended?Photoelectric Versus Ionization

Two Task GroupsFinal TG Report Findings

Combination smoke alarmsNuisance Alarm CriteriaOther ReportsEscape ScenariosCalculating Tenability

Concluding Points


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Photo and IonWhat is required or recommended?

NFPA, as an organization, recommends usingboth technologies in homes

NFPA 72 does not generally require the use ofone technology over the other

Except locations near cooking appliances

NFPA 72 does recommend the use of bothtechnologies where there is a desire for ahigher level of protection or where individualsneed extra time to escape (See A.29.1.1)


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NFPA 72 requires smoke alarms to be installedin every sleeping room, outside every sleeping

area, and on every level (See 29.5.1.1)Many older homes do not have smoke alarms in allof these minimum siting locations

NFPA 72 requires all smoke alarms to be

interconnected, unless exempted (See 29.5.2.1.1)Smoke alarms are now available with wirelessinterconnection capability


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NFPA 72 restricts the installation of any smokealarm within 10 feet of a fixed cooking

appliance (See 29.8.3.4(4))6 foot exception for smaller homes or apartmentsNo longer 3 feet from kitchen door (2002 code)

NFPA 72 restricts the installation of any smokealarm within 3 feet of a bathroom door (See29.8.3.4(5))

Both technologies are susceptible


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Photo Versus IonWhich is better?

This question has had a long historyInformal demonstration fire test videosprompted renewed interestThe NFPA 72 Technical Committee on Single-and Multiple-Station Smoke Alarms andHousehold Fire Alarm Systems appointed atask group to review issues of effectivenessUltimately two task groups worked over aperiod of about two years


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Two Task GroupsTask Group on Minimum PerformanceRequirements for Smoke Alarm DetectionTechnology Report dated February 22,2008.Task Group on Smoke Detection Follow-up

Report dated July 1, 2009


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Two Task GroupsBoth task groups reported to the NFPA 72Technical Committee on Single- andMultiple-Station Alarms and HouseholdFire Alarm Systems responsible forChapter 29 of the 2010 National Fire Alarmand Signaling Code.

Both reports are available on the NFPAWebsite at www.nfpa.org under SafetyInformation / For Consumers / Fire Safety Equipment /

Smoke Alarms / Ionization versus Photoelectric
http://www.nfpa.org/http://www.nfpa.org/


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Two Task GroupsThe first task group reported to thetechnical committee at their Report onProposals meeting in January 2008 withthe results of their work andrecommendations for follow-up work.Membership on the first task group

included technical committee membersand other interested parties


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Two Task GroupsThe second task group reported to thetechnical committee at their Report onComments meeting in October 2008 withtheir draft report.Membership on the second task groupincluded technical committee members

Other parties declined to participate


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Two Task GroupsThe work of both task groups used thedata documented in NIST Technical Note1455-1 (February 2008), Performance ofHome Smoke Alarms Analysis of theResponse of Several Available Technologies inResidential Fire Settings


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Final Report FindingsThe second task group assigned two sub-task groups

Sub-TG on Smoke Alarm Installation StrategyCombination smoke alarm performanceNuisance alarm installation criteria

Sub-TG on Performance Follow-upReview of other reportsEscape scenariosMethods of calculating tenability


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Combination Smoke AlarmsPhotoelectric alarms generally respondfaster to smoldering fires than ionization

Minutes to tens of minutes (e.g. 1.6 to 40 min)

Ionization alarms generally respond fasterto flaming fires than photoelectric

Seconds to tens of seconds (e.g. 20 to 100 sec)

Time differences depend on fire growthrate

Times estimated from SDC 01 thru 15 curves


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Combination Smoke AlarmsDual photoelectric/ionization smoke alarmsoffer the advantage both detectiontechnologies in a single unitConcern was raised in the initial reportthat the performance of dual smokealarms lagged behind that of smoke alarm

using individual technology


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Combination Smoke AlarmsThe task group reviewed the further workon dual alarms done by NIST

Performance of Dual Photoelectric/Ionization

Smoke Alarms in Full Scale Fire Tests (basedon data from NIST TN 1455)

http://fire.nist.gov/bfrlpubs/fire09/PDF/f09006.pdf

Results from a Full-Scale Smoke AlarmSensitivity Study (based on additional full-scale fire tests)

http://fire.nist.gov/bfrlpubs/fire09/PDF/f09007.pdf


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Combination Smoke AlarmsThe following conclusions were reached:

Dual alarms usually respond before ionizationalarms in smoldering fires and before

photoelectric alarms in flaming firesDual alarms are not always less sensitivethan individual alarms

Alarms using an individual technology may ormay not respond before a given dual alarmat the same location for any particular fire


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Combination Smoke AlarmsThe following conclusions were reached:

Sensitivity of off-the-shelf dual alarms usedfor comparison were more sensitive than the

ionization alarm sensitivities specified in theNIST Home Smoke Alarm reportThus for flaming fires, comparable off-the-shelfdual alarms would not be expected to alarm laterthan the responses computed for the dual alarmsin the NIST Home Smoke Alarm report


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Nuisance Alarm CriteriaFrequent nuisance alarms can result inoccupants disabling smoke alarmsThe task group reviewed availableliterature on causes for nuisance alarm

An extensive review is outlined in the 2008 TGReport with additional review provided in the2009 TG Report

Annex D of the 2009 TG report summarizesthe overall findings


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Nuisance Alarm CriteriaConclusions

Although photoelectric and ionization smokealarms are both susceptible to cooking

activities, ionization is more susceptibleBoth types should be restricted from placementnear cooking appliancesSurveys have found that smoke alarms are ofteninstalled in kitchens despite precautions in NFPA 72New restrictions on placement in NFPA 72 2010


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Placement between 10 and 20 feet fromcooking appliances

Use photoelectric or alarm silencing meansEducation on the use of the hush feature

Trade-off locating smoke alarms that useionization technology in this zone can result in ahigher potential for cooking related nuisance alarmsthan those using photoelectric technology, but canprovide an improved response to flaming fires whencompliance with minimum siting criteria requiresinstallation of a smoke alarm in this zone


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Both photoelectric and ionization smokealarms are susceptible to bathroom steam

Ionization smoke alarms are not more susceptiblePhotoelectric alarms may be more susceptiblePlacement more than 10 feet from the bathroomdoor does not appreciably reduce susceptibility

No changes with made to the mandatoryrequirements regarding the 3 foot restriction frombathroom doors. New annex material was added tosuggest placement up to 10 feet away if possible


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NFPA 72 -2010Specific requirements related to nuisance alarms

from cooking activities and bathroom steam arecontained in 29.8.3.4(4) and 29.8.3.4(5) on page72-159 of the codeDetailed explanatory annex material (includinginstallation diagrams) is contained in A.29.8.3.4(4)and A.29.8.3.4(5) on pages 72-259 through 72-262


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Other ReportsCalifornia Fire Chiefs Studies

Rodin and Graham, 1979Los Angles Fire Department, 1981

Either technology provides acceptable warningNorway report

Meland and Lonvik, 1991

UL listed alarms - either technology providesacceptable warning


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Other ReportsEngland Study

Kennedy et alDid not use smoke alarms

Did not provide correlation between sensormeasurements and actual smoke alarms


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Escape ScenariosNIST 1455-1 report escape scenarios

Assumed individuals were not in the room offire origin

Assumed occupants could escape throughalternate means of egress (windows)Not aligned with assumptions in NFPA 72

See next slide


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Escape ScenariosNFPA 72 Purpose and Assumptions29.2 (11.2)* Purpose. Fire-warning equipment for residential

occupancies shall provide a reliable means to notify theoccupants of the presence of a threatening fire and the need to

escape to a place of safety before such escape might beimpeded by untenable conditions in the normal path of egress .

29.4.1 (11.4.1) Occupants. The requirements of this chaptershall assume that occupants are not intimate with the ignition

and are capable of self-rescue.

29.4.2.3* (new) The escape route shall be along the normalpath of egress for the occupancy.


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Escape ScenariosBased on NFPA 72 assumptions, tenabilityevaluations should assume:

Escape through the normal path of egress

Individuals can be in the room of fire originand still not be intimate with ignitionIndividuals are capable of self-rescue

Evaluations should further considerindividuals that might need assistance inawakening or egress


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Calculating TenabilityNIST 1455-1 report available safe egresstimes (ASET) were evaluated as the timefrom the earliest alarm activation to the

time when any tenability limit was reachedat any location.

The first task group observed that tenabilitycalculated on that basis might produce overlypessimistic results since individuals do notnecessarily remain in a given (potentiallyworst case) location


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Calculating TenabilityThe second task group formulated arevised evaluation model

Calculate tenability based on the integrated

exposure for the individual as they movedthrough the assumed escape pathTwo assumed escape paths will be used

Direct escape path (NFPA 72 assumptions)Indirect escape path (additional travel to awakenothers and then escape)See next two slide for assumed paths


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Direct Escape Path Bedroom 1 Fire in BR 1

Indirect Escape Path Bedroom 1 Fire in BR 1

START

END

Exit

BR 3

BR 2

BR 1LivingRoomKitchen

smoke alarm response

smoke obscuration

primary gas analysistemperature

B

D

E

C

F

A

path of occupant where FED was calculated

START

START

END

Exit

BR 3

BR 2



smoke obscuration


B

D

E

C

F

A


path of occupant traveling to awaken another occupant


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Direct Escape Path Bedroom 2 Fire in LR or Kit

Indirect Escape Path Bedroom 2 Fire in LR or Kit

START

END

Exit

BR 3BR 2BR 1

LivingRoomKitchen


smoke obscuration


B

D

E

C

F

A


START

END

Exit

BR 3

BR 2



smoke obscuration


B

D

E

C

F

A



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Calculating TenabilityTenability Conditions (heat and gas)

Evaluated using equations from ISO13571:2007, Life Threatening Components of

Fires Guidelines on the Estimation of Time Available for Escape Using Fire DataConvective heat 0.30 FEDToxic gas (CO and HCN) 0.30 FED


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Calculating TenabilityTenability Conditions (heat and gas)

FED is fractional effective dose An FED of 1 corresponds to the median value of

distribution of human responses one-half thepopulation more susceptible and one-half lesssusceptible

A FED of 0.3 was used to address the moresusceptible occupants of the population

Refer to the February 22, 2008 Task GroupReport for more detailed presentation


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Calculating TenabilityTenability Conditions (smoke obscuration)

Reduced visibility was not considered anincapacitating condition but was included in

the evaluationsSome have assumed that occupants will abandonefforts to escape when visibility is reduced even ifnot overcome by heat or gasWhat reduced visibility will produce this effect?


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Calculating TenabilityTenability Conditions (smoke obscuration)

An optical density (OD) of 0.22 OD/m wassuggested by Jin for safe escape for occupants

familiar with a public building An OD of 0.25 OD/m was assumed in theNIST 1455-1 report

An OD of 0.43 OD/m was assumed by the taskgroup for residential occupants very familiarwith their surroundings

Basis in the February 22, 2008 Task Group Report


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Calculating TenabilityResults of evaluations (July 1, 2009 TG Report)

Direct escape cases - Tables 2.1a and 2.1b24 cases total

Cases SDC 34, 39 & 40 were not included in mysummary for heat, gas and visibility (testinganomalies) leaves 21Cases SDC 9 & 14 were not included in mysummary for visibility (no visibility data) leaves 19

Table 2 1a Bedroom 1 Fires Direct Escape Scenarios from Bedroom 1


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Table 2.1b Living Room and Kitchen Fires, Direct Escape Scenarios from Bedroom 2Fire in Living room

Smoldering

Alar m pr ovi des s uff ici entsafe egress time

Direct Escape

Smoke Heat Gas

SDC 1 ION Y Y YPHOTO Y Y Y

SDC 11 ION N Y Y

PHOTO N Y Y

SDC 31 ION N Y Y

PHOTO N Y Y

SDC 34 1 ION - - -

PHOTO - - -

Flaming

SDC 2 ION Y Y Y

PHOTO Y Y Y

SDC 10 ION Y Y Y

PHOTO N Y Y

SDC 12 ION Y Y Y

PHOTO Y Y Y

SDC 13 ION Y Y Y

PHOTO Y Y Y

SDC 15 ION Y Y Y

PHOTO Y Y Y

SDC 33 ION Y Y Y

PHOTO Y Y Y


SDC 41 ION Y Y Y

PHOTO Y Y Y1Test stopped before escapes times were att ained

Table 2.1a Bedroom 1 Fires, Direct Escape Scenarios from Bedroom 1Fire In Bedroom

Alar m pr ovi des s uff ici entsafe egress time

Flaming Direct Escape

Door open Smoke Heat Gas

SDC 5 ION Y Y Y

PHOTO Y Y Y

SDC 7 ION Y Y Y

PHOTO Y Y Y

SDC 38 ION Y Y Y

PHOTO N Y Y

SDC 39 2 ION - - -

PHOTO N - -

Smoldering

door closed

SDC 14 1 ION - N Y

PHOTO - Y Y

Flaming

door closed

SDC 91

ION - Y YPHOTO - Y Y

SDC 36 ION Y Y Y

PHOTO Y Y Y

Smoldering

door open

SDC 4 ION Y Y Y

PHOTO Y Y Y

SDC 6 ION N Y Y

PHOTO Y Y Y

SDC 8 ION Y Y Y

PHOTO Y Y YSDC 37 ION Y Y Y

PHOTO Y Y Y

SDC 40 3 ION - - -

PHOTO Y Y Y1No smoke measurement in room of o rigin2Test stopped before escapes times were attained3No ionization alarms available in bedrooms or corridors


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Calculating TenabilityResults of evaluations

Direct escape - heat and gas exposureIn all 21 cases with both photoelectric and

ionization alarms present sufficient safe egress timewas providedIn 20 out of 21 cases both the photoelectric andionization alarms individually provided sufficientsafe egress time

In 1 smoldering fire case the ionization alarm didnot provide sufficient safe egress time exceededheat exposure FED (bedroom door closed)


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Direct escape - smoke obscurationIn 17 out of 19 cases with both photoelectric and

ionization alarms present sufficient safe egress timewas providedIn 14 out 19 cases both the photoelectric andionization alarms individually provided sufficientsafe egress time

Continued next slide


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Direct escape - smoke obscurationIn 2 flaming fire cases, the photoelectric alarms did

not provide sufficient safe egress timeIn 1 smoldering fire case, the ionization alarm didnot provide sufficient safe egress timeIn 2 smoldering fire cases, neither the photoelectricor ionization alarm provided sufficient safe egresstime


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Calculating TenabilityResults of evaluations (July 1, 2009 TG Report)

Indirect escape cases - Tables 2.2a and 2.2b24 cases total

Cases SDC 33, 34, 35, 39 & 40 were not included inmy summary for heat, gas and visibility (testinganomalies) leaves 19Cases SDC 9 & 14 were not included in mysummary for visibility (no visibility data) leaves 17

Table 2.2a Bedroom 1 Fires, Indirect Escape Scenarios from Bedroom 1


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Table 2.2a Bedroom 1 Fires, Indirect Escape Scenarios from Bedroom 1Fire In Bedroom

Alar m pr ovi des s uffi cien tsafe egress time

Flaming Indirect Escape

Door open Smoke Heat Gas

SDC 5 ION Y Y Y

PHOTO Y Y Y

SDC 7 ION Y Y Y

PHOTO N Y Y

SDC 38 ION Y Y Y

PHOTO N Y Y

SDC 39 2 ION - - -

PHOTO N - -

Smoldering

door closed

SDC 14 1 ION - N N

PHOTO - Y Y

Flaming

door closed

SDC 91

ION - Y YPHOTO - N Y

SDC 36 ION N Y Y

PHOTO N N Y

Smoldering

door open

SDC 4 ION N Y Y

PHOTO Y Y Y

SDC 6 ION N Y Y

PHOTO N Y Y

SDC 8 ION N Y Y

PHOTO Y Y YSDC 37 ION Y Y Y

PHOTO Y Y Y

SDC 40 3 ION - - -

PHOTO Y Y Y1No smoke measurement in room of origin2Test stopped before escapes times were attained3No ionization alarms available in bedrooms or corridors

Table 2.2b Living Room and Kitchen Fires, Indirect Escape Scenarios from Bedroom 2Fire in Living room

Alarm pro vid es suf fic ientsafe egress time

Indirect Escape

Smolderin g Smoke Heat Gas


SDC 11 ION N Y Y

PHOTO N Y Y

SDC 31 ION N Y Y

PHOTO N Y Y

SDC 34 1 ION - - -

PHOTO - - -

Flaming

SDC 2 ION Y Y Y

PHOTO N Y Y

SDC 10 ION N Y Y

PHOTO N N N

SDC 12 ION Y Y Y

PHOTO Y Y Y

SDC 13 ION Y Y Y

PHOTO Y Y Y

SDC 15 ION Y Y Y

PHOTO Y Y Y

SDC 33 ION Y Y Y

PHOTO 1 - - -

SDC 35 ION Y Y Y

PHOTO 1 - - -

SDC 41 ION Y Y Y

PHOTO Y Y Y1Test stopped before escapes times were attained


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Indirect escape - heat and gas exposureIn all 19 cases with both photoelectric and

ionization alarms present sufficient safe egress timewas providedIn 15 out of 19 cases both the photoelectric andionization alarms individually provided sufficientsafe egress time



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Indirect escape - heat and gas exposureIn 2 flaming fire cases, the photoelectric alarm did

not provide sufficient safe egress time exceededheat exposure FED (bedroom door closed)In 1 flaming fire case, the photoelectric alarm didnot provide sufficient safe egress time exceededheat and gas exposure FED

In 1 smoldering fire case, the ionization alarm didnot provide sufficient safe egress time exceededheat and gas exposure FED (bedroom door closed)


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Indirect escape - smoke obscurationIn 12 out of the 17 cases with both photoelectric

and ionization alarms present sufficient safe egresstime was providedIn 7 out 17 cases both the photoelectric andionization alarms individually provided sufficientsafe egress time



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Indirect escape - smoke obscurationIn 3 flaming fire cases, the photoelectric alarms did

not provide sufficient safe egress timeIn 2 flaming fire cases, neither the photoelectric orionization alarm provided sufficient safe egress timeIn 2 smoldering fire cases, the ionization alarm didnot provide sufficient safe egress timeIn 3 smoldering fire cases, neither the photoelectricor ionization alarm provided sufficient safe egresstime


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TG majority consensusThe response to direct escape scenarios was

adequate for either technologyPossible exception: fires in bedrooms with doors closedNeither technology appears to offer an advantagefor nonspecific firesFor indirect escape scenarios the use of bothtechnologies is a definite benefit and isrecommended

Where more time is needed to awaken and/or assist others


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TG minority opinion Annex C of final TG report

Recommended requiring both technologies inbedroomsBedroom locations benefit most from using bothtechnologiesPhotoelectric only 67%, ionization only 71%, both 92%

Assumes both direct and indirect cases, smoke, heat & gasImprovement using both technologies in otherlocations not significant


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Concluding PointsExclusion of ionization technology

The need for protection from both smolderingand flaming fires is fundamental

Excluding ionization technology ignores thebenefits of using of both types together

Photo and ion individually or combination photo/ion


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Concluding PointsRestricting ionization technology within 20ft of kitchen doors

Basis for 20 ft from kitchen door?

Ignores the benefits of using bothtechnologies together beyond 20 ft of cookingappliances


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Concluding PointsRestricting ionization technology within 20ft of bathroom doors

Basis for 20 ft from bathroom door?

Photoelectric technology is not less susceptibleto bathroom steamThere is little benefit of restricting either typebeyond 10 feet of bathroom doorsIgnores the benefits of using both typestogether in most bedrooms


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Concluding PointsSmoke alarm installations

All homes (regardless of age) should havesmoke alarms installed in the minimum siting

locations prescribed in NFPA 72Outside each sleeping areaOn every levelInside every sleeping room

All home smoke alarms should beinterconnected

Especially important for larger homes


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SMoke Alarm Detection Technology

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