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Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and Flame Retardants

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.

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Modelling Fire Scenarios in Residential Buildings with Respect to the Benefit of Smoke Detectors and Flame Retardants

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

  2. European Home Fires • 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

  3. 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) Smoke Detectors / Flame Retardants

  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. NIST study about smoke detector performance (2004) Experimental studies, e.g. Babrauskas (1988), CBUF, Hirschler, Troitzsch (1998), LCA (2000 - 2003) Fire test of the Berlin fire service (2005) Fire test of BAM / Berlin fire service (2006) Validation Time to Flashover: 2 - 17 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) Experimental Data

  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. Validation: Manufactured House

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

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

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

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

  14. Subsidised home Living room

  15. Subsidised home Smoke detectors Living room

  16. Subsidised home : Furniture Smoke detectors Living room

  17. Input data: HRR sofas

  18. Fire Spread First burning item = sofa

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

  20. Smoke: Visibility 4 m 30 s 60 s

  21. Burning TV sets: HRR

  22. Burning TV sets

  23. Berlin Fire Service: Fire Test

  24. Comparison

  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. Fire test in children‘s room Extract from RTL coverage

  27. Model Geometry

  28. Predicted and Measured Temperatures Room centre Right front corner

  29. Predicted Temperatures in Children‘s Room - Using a FR Mattress

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

  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. Thank you for your attention !

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