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

BAMDepartment VII Safety in StructuresDivision Fire Engineering

By Rudi Bormsmember of the exec. comm.of EFRA

Project sponsored by EFRA

Budapest June 14th-15th 2007

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• 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

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)

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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

Experimental Data

• 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)

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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

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Validation: Manufactured House

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Validation A1: Given HRRHeat release rate of flaming chair:

(not completely consumed by fire)

Chair heat release rate

0

40

80

120

160

0 50 100 150 200 250

time [s]

Hea

t re

leas

e ra

te [

kW]

Submodels / input data:

• Chemical reaction

• Smoke production

• Radiation

• Turbulence

• Material properties for upholstery

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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

Predicted and measured temperatures in living room

20

45

70

95

120

145

170

0 50 100 150 200 250 300 350 400

Time [s]

Tem

per

atu

re [

°C]

FDS E_liv 2.38

FDS E_liv 1.50

FDS E_liv 1.18

FDS E_liv 0.58

'TCE_1 '

TCE_4

'TCE_5 '

'TCE_7 '

FDS: lines

Data: markers

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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

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Validation A2: Full chemical model

Submodels / input data:

• Chemical reaction

• Smoke production

• Radiation

• Turbulence

• Material properties for upholstery

13

A2: Predicted and measured temperatures

20

45

70

95

120

145

170

0 50 100 150 200 250 300 350 400

time [s]

tem

per

atu

re [

°C]

E_liv 2.38

'TCE_1 '

20

45

70

95

120

145

170

0 50 100 150 200 250 300 350 400

time [s]

tem

per

atu

re [

°C]

E_liv 2.10

'TCE_2 '

20

45

70

95

120

145

170

0 50 100 150 200 250 300 350 400

time [s]

tem

per

atu

re [

°C]

E_liv 1.79

'TCE_3 '

20

45

70

95

120

145

170

0 50 100 150 200 250 300 350 400

time [s]

tem

per

atu

re [

°C]

E_liv 1.50

'TCE_4 '

FDS: lines

Data: markers

Ignition time predicted too early

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Subsidised home

Living room

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Subsidised home

Living room

Smoke detectors

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Subsidised home : Furniture

Living room

Smoke detectors

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Input data: HRR sofas

0

500

1000

1500

2000

2500

3000

0 500 1000 1500 2000 2500 3000 3500 4000

time in s

HR

R i

n k

W

Non-FR, SFPE Handbook

P-FR, LCA data

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Fire Spread

First burning item = sofa

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Predicted temperatures

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800 900

time in s

tem

pe

ratu

re in

°C

P-FR-LCA, living room 2.2 m

P-FR-LCA, living room 1.5 m

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700 800 900

time in s

tem

pe

ratu

re in

°C

sofa-SFPE, living room 2.2 m

sofa-SFPE, living room 1.5 m

120°C

600°C

130 s 730 s

FR sofaNon-FR US sofa

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Smoke: Visibility

0

5

10

15

20

25

30

35

0 50 100 150 200

time in s

visi

bilty

in m

0

5

10

15

20

25

30

35

0 50 100 150 200

time in s

visi

bili

ty in

m

30 s 60 s

4 m

21

Burning TV sets: HRR

0

50

100

150

200

250

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

time [s]

He

at

rele

as

e r

ate

[k

W]

Non-flame retardant LCA (TV)Sweden small ignition source

FlameRerardant LCA (TV) US.

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Burning TV sets

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Berlin Fire Service: Fire Test

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Comparison

Observations in Fire Test Numerical model

Only TV burns 6:20 min 6:10 min

Shelf burns 8:30 min 7:00 min

Flashover 10:30 min 7:52 min

Flames out of window 11:00 min 9:00 min

Smoke detector 4:47 min 1:30 min

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Children's room

• Accumulation of high risk items

– Mattresses

– Upholstery

– Electrical devices (TV sets, computer)

– Toys (plastic)

• Wrong behaviour:

– Playing with fire

– Hiding

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Fire test in children‘s room

Extract from RTL coverage

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Model Geometry

Observations Fire test Numerical model

Only lower mattress burns

1:30 min 2:10 min

Lower and upper mattress burn

3:00 min 3:00 min

Flashover 4:00 min 3:45 min

Flames out of window

4:30 min 4:00 min

Smoke alarms

2:00 / 2:23 min

0:37 / 1:05 min

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Predicted and Measured Temperatures

0

200

400

600

800

1000

1200

100 150 200 250 300

Time in s

Te

mp

era

ture

in

°C

FDS 0,5

FDS 1,5

FDS 1,85

FDS 2,15

Data 0,5

Data 1,5

Data 1,85

Data 2,15

0

200

400

600

800

1000

1200

150 170 190 210 230 250 270 290

Time in s

Te

mp

era

ture

in °

C

FDS 0,5

FDS 1,5

FDS 1,85

FDS 2,15

Data 0,5

Data 1,5

Data 1,85

Data 2,15

Room centre Right front corner

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

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6 7

time [min]

tem

pera

ture

[°C]

non FR 2.15 m

non FR 1.50 m

FR 2.15 m

FR 1.50 m

non FR

FR

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Flame retardants have impact on fire safety

Numerical results:

• Lower temperatures in the room

• Benefit of additional escape time

• Additional time to flashover

Conclusions

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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

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Thank you for your attention !