© Institut de Sécurité 1 Sprinklers for Two New Swiss Detention Buildings Jerzy Respondek Swiss...

© Institut de Sécurité

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Sprinklers for Two New Swiss Detention Buildings

Jerzy Respondek Swiss Institute of Safety and Security

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AHJ requirements (health care occupancies): automatic smoke detection system, HVAC (continuously operating) – automatic smoke dampers and independent ducts

(supply and exhaust), adjacent corridor – mechanical smoke exhaust system built accordingly to French

fire codes (6th International Conference on Performance – Based Codes).

Operator requirements: main threat – deliberately set fires (fast fires), cells shall be protected by special quick response sprinklers, HVAC shall function continuously even in case of fire, adjacent corridor shall be protected by special mechanical smoke exhaust system

(exhaust and supply air velocity ≤ 1.0 m/s), chapter n°22 of NFPA 101® “Life Safety Code”.

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■ Common Fire Safety Features for Both Concepts: Detention Cells:- interphone-connexion with the control room constantly attended by prison

staff,- alarm button connected to the control room,- automatic fire alarm (smoke detector / sprinkler) transmission to the control

room. Corridors:- manual fire boxes inside locked cabinets with fire hoses and portable

extinguishers,- emergency lighting,- exit signs will be provided only in areas accessible to the public,- special mechanical smoke exhaust system designed on the basis of fire

simulations.

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Staff intervention, alarm and communications systems.

- At first stage, the alarm notification will be limited to staff (pagers etc.) present inside the building or occupying the permanently attended central control room.

- Alerted staff occupying the control room will ensure the notification of the fire department.

- In case of fire, the alerted staff intervening without protective clothing / breathing apparatuses shall be able to rescue the occupant of the fire cell within 2.0 minutes after the reception of the fire alarm.

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■ Fire Scenario Developed for the Purposes of Fire Simulations.

The accepted by AHJ fire scenario of the deliberately set fire located on the bed of the detention cell, will be based on the ignition and combustion of the following items:

1.93 kg of clothing and paper [Babrauskas], two 0.65 kg polyurethane pillows [Babrauskas], special mattress composed of fire retarded polyurethane

padding covered by PVC sheets and used in European detention buildings [CBUF Reasearch Program].

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0.00E+00

1.00E+02

2.00E+02

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0.00E+00 1.00E+02 2.00E+02 3.00E+02 4.00E+02 5.00E+02 6.00E+02 7.00E+02 8.00E+02 9.00E+02 1.00E+03

sec.

kW

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■ The preliminary simulations of possible flame spread on the real combustible items of the fire seat have shown that using FDS ver. 4. 07 to develop the similar HRR history to this illustrated by the above figure, will practically always lead to the different evolution of the HRR (less pessimistic) which would not be accepted by AHJ.

■ For these reasons the final simulation were carried out for the assumption, that the fire will behave in a manner similar to a burner of polyurethane foam emitting the product of combustion corresponding to the nature of the concerned combustible [Tewarson].

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Fire Safety Concept based on the Installation of Smoke Detectors: Results of Fire Simulations.

■ Ventilating and air-conditioning system of the detention cell.

- Location of the exhaust duct / grille: on the wall of the shower cell and in the case of fire, the ventilators will be turned off followed by the closing of the fire dampers.

- Velocity of exhausted air flowing through the duct before stopping the system: ≈0.8 m/s.

- Exhaust rate of the system during non fire conditions: 60.0 m³/hour.

- Supply of fresh air during the fire: through the undercut (height of 0.03m) of the access door to the detention cell.

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■ Simulation of smoke detector activation.

- Location of scattering detector: inside the exhaust duct (behind the grille placed on wall of shower cell).

- Simulation method: Heskestad model.- Selected characteristic length of the smoke detector: 3.0 m

(based on the results of tests carried by the manufacturer in the room of similar dimensions and the evaluation of the paper pulished by Björkman).

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Main results of fire simulations and some comments.

■ Despite the rapid reaction of smoke detector (30.0 seconds after the ignition of the first combustible item) the staff's members at their arrival (150.0 second after the ignition of the fire) will face the fully smoke logged cell.

■ The temperature inside the cell (350.0°C) will rule out any attempt to rescue the occupant of the cell by staff intervening without protective clothing and breathing apparatuses.

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Concept based on the Installation of Sprinkler System: Fire Simulations Results.

■ Specific design features of the sprinkler:- sprinkler type: special designed for detention buildings,- RTI of sprinkler link: ≤ 50.0 (ms)^0.5,- reaction temperature of the sprinkler link: 58.0°C,- K-factor: 80.0 l / min∙bar,- required water pressure: 1.0 bar,- distance between the sprinkler link and the fire seat: 1.1 m,- distribution of water droplets: database of FDS fire model,- simulation of sprinkler link reaction: standard model included in

FDS fire model.

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■ Simulation of fire suppression by water sprays delivered on the burning items.

Due to the fact that the fire will be simulated as a burner of polyurethane foam, it was agreed with AHJ that the calculation of progressive reduction of the HRR of the fire will be based on the use of the algorithm developed by Evans for unshielded fires.

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Fig.n°1

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Some comments to the results of fire simulations.

■ The prompt reaction of sprinkler link and efficient functioning of continuously running HVAC system of the detention cell will permit to maintain the tenable conditions at the height of 1.0 m above the floor of the cell (max.temperature-70.0 °C; max. CO concentration-600.0 ppm).

■ 30.0 seconds after the opening of cell's door, the staff members intervening without protective clothes and breathing apparatuses would be able to penetrate inside the cell and rescue the occupant lying on the floor of the cell.

■ The fire simulations accepted by AHJ too, have confirmed the technical feasibility of NFPA 101 ® provisions which shall be applied in case of construction of new detention buildings.

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The level of life safety within the cells would be certainly better than currently achieved in Swiss residential buildings.

The implementation of this concept will contribute to the considerable reduction of construction (≈ 250.0k USD) costs due to the reduction of fire resistance of elements bounding the cells (doors, walls) and simplification of the HVAC system structure (suppression of smoke / fire dampers etc.).

It seems that the same approach could be used for other

buildings containing rooms equipped with continuously operating HVAC systems (health care occupancies, hotels etc.).

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■ Short Description of Supplementary Fire Simulations. Medium and slow accidental fire. Very small fire of 1.0 kW.

The main results of these simulations: In case of 1.0 kW accidental fire, the continuously operating

HVAC system would maintain the tenable conditions inside the cell and this during 15.0 minutes of simulations,

For the smallest accidental slow fire (15.0 kW), the reaction of guards alerted by operation of sprinkler link (3.0 minutes after the ignition of first combustible items), will take place well before occurrence of untenable conditions inside the cell.

These results agrees very well with the conclusion of one experimental study carried out in one Canadian detention building

© Institut de Sécurité 1 Sprinklers for Two New Swiss Detention Buildings Jerzy Respondek Swiss...

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