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Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and Flame Retardants Reporting of a study made by Dr.

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Presentation on theme: "Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and Flame Retardants Reporting of a study made by Dr."— Presentation transcript:

1 Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and Flame Retardants Reporting of a study made by Dr. Anja Hofmann BAM Department VII Safety in Structures Division Fire Engineering By Rudi Borms member of the exec. comm. of EFRA Project sponsored by EFRA Budapest June 14th-15th 2007

2 2 Hazardous home fires: 80 % of all fire fatalities in homes Fire spread is very fast: only 2 to 4 minutes escape time after fire detection, earlier tests in 1970s described longer escape times. Different concepts in Europe to minimise fire losses: Smoke detectors and flame retardants European Home Fires

3 3 Smoke Detectors / Flame Retardants Valuable to wake and warn sleeping persons Escape time (2 to 4 minutes) is very short, especially for very young, older or disabled persons Batteries have to be changed regularly Flame retardants lead in general to later (or no) ignition and lower the heat release rate of the burning item Only several items of furniture are equipped with flame retardants (e.g. upholstery or television sets)

4 4 High Risk Items Upholstery: a single item could cause flashover in a room TV: 2 to 3 min to peak of HRR, lot of smoke (faster development than refrigerator/washing machine, lower peak) Toys: easy ignition with lighter after 1 to 3 sec, burning for up to 25 min

5 5 Experimental Data NIST study about smoke detector performance (2004) Experimental studies, e.g. Babrauskas (1988), CBUF, Hirschler, Troitzsch (1998), LCA ( ) Fire test of the Berlin fire service (2005) Fire test of BAM / Berlin fire service (2006) Validation Time to Flashover: min. (Non-FR) 20 min - (FR) HRR for single items, e.g. upholstery, TV sets 10:30 min (Non-FR) 4:00 min (Non-FR)

6 6 CFD (Computional Fluid Dynamics) Field model: room is divided into cells (FVM) Balances of mass, momentum, energy Submodels: chemical reaction, radiation, soot, turbulence; and material parameters Furniture with and without flame retardants Different home geometries, closed and open windows Smoke detectors Results: temperatures, velocities, gas concentrations in the room, smoke production and smoke movement

7 7 Validation: Manufactured House

8 8 Validation A1: Given HRR Heat release rate of flaming chair: (not completely consumed by fire) Submodels / input data: Chemical reaction Smoke production Radiation Turbulence Material properties for upholstery

9 9 Validation A1: Given HRR Submodels / input data: Chemical reaction Smoke production Radiation Turbulence Material properties for upholstery

10 10 A1:Predicted(FDS) and measured (TCE)temperatures FDS: lines Data: markers

11 11 Validation A2: Full chemical model Ignition: spark for 20 s Material: upholstery (NIST data) Reaction: polyurethane (FDS: NFPA Handbook, Babrauskas) Submodels / input data: Chemical reaction Smoke production Radiation Turbulence Material properties for upholstery

12 12 Validation A2: Full chemical model Submodels / input data: Chemical reaction Smoke production Radiation Turbulence Material properties for upholstery

13 13 A2: Predicted and measured temperatures FDS: lines Data: markers Ignition time predicted too early

14 14 Subsidised home Living room

15 15 Subsidised home Living room Smoke detectors

16 16 Subsidised home : Furniture Living room Smoke detectors

17 17 Input data: HRR sofas

18 18 Fire Spread First burning item = sofa

19 19 Predicted temperatures 120°C 600°C 130 s 730 s FR sofa Non-FR US sofa

20 20 Smoke: Visibility 30 s60 s 4 m

21 21 Burning TV sets: HRR

22 22 Burning TV sets

23 23 Berlin Fire Service: Fire Test

24 24 Comparison Observations in Fire TestNumerical model Only TV burns6:20 min6:10 min Shelf burns8:30 min7:00 min Flashover10:30 min7:52 min Flames out of window11:00 min9:00 min Smoke detector4:47 min1:30 min

25 25 Children's room Accumulation of high risk items –Mattresses –Upholstery –Electrical devices (TV sets, computer) –Toys (plastic) Wrong behaviour: –Playing with fire –Hiding

26 26 Fire test in childrens room Extract from RTL coverage

27 27 Model Geometry ObservationsFire testNumerical model Only lower mattress burns 1:30 min2:10 min Lower and upper mattress burn 3:00 min Flashover4:00 min3:45 min Flames out of window 4:30 min4:00 min Smoke alarms 2:00 / 2:23 min 0:37 / 1:05 min

28 28 Predicted and Measured Temperatures Room centre Right front corner

29 29 Predicted Temperatures in Childrens Room - Using a FR Mattress

30 30 Flame retardants have impact on fire safety Numerical results: Lower temperatures in the room Benefit of additional escape time Additional time to flashover Conclusions

31 31 Combination of both safety technologies Smoke detectors warn inhabitants of fire and smoke; no impact on fire development Use of flame retardants / appropriate materials is advisable for high risk items: Reduction of flammability and heat release

32 32 Thank you for your attention !


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