Q&As Concerning Fire of Flexible Polyurethane
Foams: Hazards and Prevention«For Houses and Buildings»

March

2010

Final Report

Translation into English by JUIITechnology and Safety Committee
Fire Safety Working Group1

Introduction
These Q&As have been made as part of our ongoing efforts for risk management in fire safety.
A variety of polyurethane foams are used in the building and housing sector in many applications
depending on their characteristic properties. Flexible polyurethane foams are not presently used as building
materials regulated by the Building Standard Law or similar regulations, but are widely used in houses andother buildings in various applications.
Occurrences of fire continue in spite of many measures taken, including efforts of providing improved fire
proof materials. The Japan Urethane Industry Institute (JUII) has been conducting activities foradvancement of fire safety.
Fire prevention activities thus far carried forward by the Fire Safety Committee includes publication of
Q&As on rigid polyurethane foams.
The following Q&As on flexible polyurethane foams are intended to call attention to the hazards of fire, interms of secondary ignition in particular, of flexible polyurethanes used widely as interior goods andproducts in the house.
The members of the Committee have read carefully, and construed as fairly and properly as possible,
publicly known information, including JUII’s official booklets and information on its home page,, and havemade use of such information in editing these Q&As as model answers .
Please bear in mind that these Q&As have been edited from the viewpoint of risk management and do notreflect the official positions of JUII.
It is our strong desire that these Q&A would help win understanding of people who handle or use flexible
polyurethane foams about the hazards and prevention of fire.

16thMay 2010
Japan Urethane Industry Institute (JUII)Technical and Safety Committee
Fire Safety Working Group2

Content◆

Application

Q1.

In what applications are flexible polyurethane foams used in the construction sector?
･･････････････････5◆Fire incident

Q2.

I’d like to know some instances of fire of flexible polyurethane foams that occurred in Japan.
･･････････････････5

Q3.

What are typical causes of fire accidents of flexible polyurethane foams?
And will you give some instances that occurred in overseas countries?

◆･･････････････6

Fire Behaviour

Q4． What is the amount of combustible matter placed in an average house? Will you･･････････････････6

describe the burning behaviors of such combustibles?
Q5.

What is the phenomenon of flashover occurring during a fire? Will it occur when flexible
Polyurethane foam is burning?

･･･････････････8Q6.

What phenomenon do you call smoldering?

････････････････8Q7.

Why does flame spread faster after it reaches the ceiling?

Q8.

In a fire involving polyurethane foams, to what degree will the room temperature rise?

････････

9･･････････････10Q9.

What should be done when flexible polyurethane foams catch fire?

Q10.

Will you give the ignitability of flexible polyurethane foams?

◆･････････10･･･････････････10

Combustible characteristic

Q11． Will you give the flash point, fire point and oxygen index of flexible polyurethane foams?
･･････････12･････13

Q12． Will flexible polyurethane foam products combust spontaneously?

Q13． Is the combustion rate of flexible polyurethane foams faster than other materials? ･･･････13
Q14．It is told that plastic materials emit much smoke when burned. How about polyurethane･･･････････････････････16

foams?
Q15．Do flexible polyurethane foams catch fire easily?

･･････････････････････17

Q16．What is the degree of the heat resistance of flexible polyurethane foams? ････････････････17
Q17．Won’t flexible polyurethane foams ignite by sparks of static charges built up in them?
･･････････････････････17
Q18．Can flexible polyurethane foams be made fire retardant?

3

･･18

Q19．Do flexible polyurethane foams differ in combustibility from plastic foams used as･･･････････18

building interior materials?

Q20．Do flexible polyurethane foams for upholstery application differ in combustibility from･･････････18

other plastic foams?

････18

Q21．When flexible polyurethane foams burn, what gases will be emitted?

Q22 If gas or smoke emitted by flexible polyurethane foams on fire is inhaled, what influences･･･21

will occur to the body of the inhaler and what measures should be taken?
Q23．When flexible polyurethane foams are set on fire, what is the amount of smoke emission･･･････････22

compared with other plastic materials？

･･････････23

Q24．What sort of products are low-combustibility polyurethane foams?

･･････23

Q25．Do combustion gases of flexible polyurethane foams contain toxic constituents?

････････････24

Q26．What gases will be emitted during smoldering?

◆

Test Method･･･････････25

Q27． What are typical combustion tests of flexible polyurethane foams?
Q28． Can we find the combustibility of polyurethane foams by simple means?

･･･････････26
Q29．What materials fall within the interior finishing certified by test under the Building･････････････27

Standard Law ?
Q30．What does “interior finishing restriction” signify?

･････････････28

Q31．Are flexible polyurethane foams regulated by the interior finishing restriction?

･･･････29････････････29

Q32．Does the Fire Service Law regulate the interior materials?

Q33．Are there any differences in the combustion test of interior materials(decoration usage)･･･････････30

in Japan and in foreign countries?

◆

Activity of fire prevention

Q34．What care is required to prevent fire?

･･･････････30

Q35.

What educational activities for fire prevention are you engaged in?

･･････････32

Q36.

What other points require attention in handling flexible polyurethane foams?

･････････32

Appendix

・・・・・・・・・・・・・・・・・・34

Postscript･･････････ 35

4

Q1． In what applications are flexible polyurethane foams used in the construction sector?
A:

Flexible polyurethane foams are rarely used in the construction sector. An example of specialty

applications is sound insulation of acoustic chambers such as studios.

Q2． I’d like to know some instances of fire of flexible polyurethane foams that occurred in Japan.

A:Fire accidents that occurred in the past include combustion of sofa cushions of flexible
polyurethane materials resulting in burning down of a building and combustion of polyurethanemats on the floor that caused burning down of a gymnasium.
Table2the recent typical fire incidents in Japan

Month Year

Occurrence location

3.1995

Gunma prefecture

Cause

Situation of the occurrence

Spark in the

When the blade of the cutter is ground with thepolishing

grinder, the flying spark ignited to thepolyurethane rubbish scattered on a surrounding
floor at the polyurethane foam processing factory.
NO personal damage

11.2001

Okayama prefecture

Short of wiring

The power wiring such as cutters is shortcircuited at the polyurethane foam manufacturing
factory, the electric wire tube is melted, it sets
sparks flying, and the polyurethane foam is
ignited.
NO personal damage

10.2001

Physical exercises

Playing with

It broke out in university gym 3F only for

gym in Tokyofirephysical exercise, the polyurethane foam matburnt, and the spreading expansion was done
rapidly.
NO personal damage

10.2002

Mie prefecture

Spark in the

At the polyurethane foam processing factory, thepolishingspark of the grinder that grinds the blade of
cutter ignites the polyurethane foam in thevicinity.
NO personal damage

10.2008

Private video shop in

Arson

The sofa made of polyurethane foam etc. burn by

Osakaarson in the private video shop at midnight, and it
spreaded in a short time.
15 persons failed to escape killed
10 persons injured

5Q3． What are typical causes of fire accidents of flexible polyurethane foams? And will you give someinstances that occurred in overseas countries?
A:

The Fire Service White Paper for Fiscal 2007 lists, as causes of housing fire, arson, stove, andcigarette in the order of most occurrences. Fires of houses have occurred from careless handling of small
fire sources such as cigarettes leading to burning of sofas, mattresses, pillows, sheets or other personal
belongings. Many buildings other than houses, public buildings in particular, contain upholstery andacoustic materials of flexible foams (See Q1). During interior work, fire may break out of welding or
cutting sparks sticking to such materials.
Overseas instances include fire disasters caused by sparks of toy fireworks sticking to upholstery
flexible foams. Flexible polyurethane foams should be kept away from any fire sources. The table below
shows instances of overseas fire accidents.

Table3 Fire incident (oversea)
Month/

Location

Outline of fireYear
Jan. 2009

Jan. 2009

Damage situation
Death toll

Bangkok in The fire of fireworks emitted in the new year celebration 60persons killed
Thailand

ignites the interior material in the night club.

212persons injured

Fujian、The fire of fireworks where the guest originates ignites

17persos killed

in China

the polyurethane foam for the decoration of the ceiling

22persons injured

in a Latin system bar.
Sept.2008

Shenzhen

The fire of fireworks has spread to the building though

43 persons killed

In China

fireworks show "Night of the indoor fireworks" was88persons injured

seen at the Shenzhen night club.

Q4． What is the amount of combustible matter placed in an average house?
Will you describe the burning behaviors of such combustibles?
A: The wooden house combustibles consist of live fire load, that is, furniture, bedding, interior cloth andother combustible matter placed in a house, and the building structures such as pillars and beams.
Reportedly, an average wooden house has live fire load of 30-50kgs per square meter in terms of timber
and about 80kgs of building structures. A house contains many combustible substances. According to theFire Service White Paper, by far the greatest number of ignition instances occur with a ‘futon’ and thethings attached to it, which amounts to double the number of instances of clothing that rank second. This
indicates that fire tends to spread to things nearby. Most of the things in the room that may catch fire are
furniture and other live load items rather than interior finishing. If many pieces of furniture cover thewalls, it must be said that a situation would arise in which the incombustible interior finishing would
turn to combustible.

6

The fire safety verification method prescribed in the Building Standard Law is based on the premise ofstandard fire spread behavior. However, things in a house are various and their burning behaviors vary
accordingly. Combustible furniture, fixtures, interior goods and products can be made incombustible orflame retardant so that the time to ignition may be retarded. The retarded time to ignition will retard gas
evolution and reduce the quantity of gases evolved. Fig. 4 shows heat releases of typical combustibles.
Houses seldom undergo evacuation safety verification, but the Enforcement Ordinance of the BuildingStandard Law stipulates the limit of heat release from live fire load in a houseroom in the provisions of
its Article 108-3, Paragraph 2, Item 1. It is 720MJ/m2 and is the second highest, following the figure forthe salesroom of the department store of 960MJ/m2. Such stipulated limits of heat release will be thebasis for the respective evacuation safety verifications.
Ｔａｂｌｅ 4 Test result of heat release rate and total caloric valueof the typical storage combustible material
Storage combustible
material

B
E
D
D
I
N
G

Initial weight（g）Max. heat release
rate （kw）

Total caloric
value （MJ）

Pillow １

1550．0No- burning

No- burning

Pillow 2

1360．0No- burning

No- burning

Blanket made of toweling（thick）

1825．0

306.3

35.1

Blanket made of toweling（thick）

761.0

213.0

14.1

Fur

1287.0

103.7

20.2

Sheet

490.0

360.0

10.0

Futon １3790.015.0

14.2

Futon 2

2200．0

120.0

15.0

Futon 34240.054.0

18.0

Mattress １

1850.0

178.1

44.9

Mattress 2

1830.0

121.2

37.7

Mattress 3

1690.0

298.4

39.5

Mattress 4

1840.091.7

44.0

Mattress 5

1590.0

112.8

35.1

Source: Combustibility of storage combustibles as a design fire
Source for fire safety design , BRI‐H18 course text
Fig4 Death toll of housing fire by Ignition material in 2007
( except arson/suicide）
tempura fat
2%
curtain/carpet4%
textile5%gasoline/kerosene
6%gas other
0% 10%

Death by housing fire
1148 persons
bedding sort27%

furniture6%
clothing
15%

paper
7%
interior/
fitting
9%

waste
9%

Source： fire white paper in 20087Q5． What is the phenomenon of flashover ?
Will it occur when flexible polyurethane foam is burning?
A:

Heat of fire accumulated within a room that is on fire will raise the temperature of the combustible

materials such as ceilings, walls and furniture up to a point of ignition and cause sudden combustion of
the entire room followed by quick spread of fire. This is called a flashover. (See Fig.1 of Q8)
If the furniture and other things in the room are flammable, the fire tends to spread quickly up to aflashover. Thus the burning behavior of the walls, ceilings, interior materials and other combustibles inthe building will greatly affect the flashover.
Polyurethane foams as well as other combustibles will, if a fire is spreading, contribute to the occurrenceof a flashover. The photo below shows a full size experiment of burning. When a flashover (FO) occurs,
the rate of heat generation will rise sharply. From the occurrence of the flashover on, the concentration of
CO2 will rapidly increase and the CO concentration will also increase. Another phenomenon that will
occur is an increase of smoke emission.

Fig5. Phenomenon of Flashover in room corner
test (ISO 9705)

HRR (kW)

1000
750
500
250
300KW

100KW

0
0

300

600

900

1200

Time (sec)
The gas burner of the room corner (generation of heat speed 100KW for 0-10 minutes
and then 300KW for another 10 minutes ) is ignited and the combustion expansion
along the surface of the interior is measured.

Q6．
A:

What phenomenon do you call smoldering?
Smoldering means flameless combustion accompanied by smoke emission. An example is a burningcigarette or incense stick. Another is a ‘futon’ burning without emitting flame for a while after a lit
cigarette is dropped on it.
If combustible gases evolved by thermal decomposition do not form a combustible gas mixture due
to low ambient oxygen concentration or any other reason, flaming will not occur and just carbonaceous
residue will burn. Such combustion is called smoldering. During smoldering, combustible gases evolvedby thermal decomposition may be cooled to emit whitish smoke. It is known that, when ambient oxygen
concentration becomes higher, the phenomenon of smoldering may turn to flaming and, when oxygen

concentration becomes lower, flaming turns to smoldering.
In case of fire of polyurethane foams, even if flame disappears and is believed to have been put out, thefoams may be smoldering. The fire must be extinguished to the bottom.

8

Fig6 Flow of heat and materials on the smoldering
smoke

nt
rre
Cu

i
of a

r

Carbon monoxide
Carbon dioxide

oxygen

ash
heat

heat

Solid residue

Sp
rea

din
g

Thermaldecomposition

Source： fire VOL.39(5) , JAFSE

Q7． Why does flame spread faster after it reaches the ceiling?
A: After reaching the ceiling by upward propagation, flame is promoted to spread over the ceiling surface
by buoyancy. If the ceiling is made of combustibles, the speed of flame spread will increase rapidly.
Even if the ceiling is made of incombustibles, the radiant heat source will expand, and intensified
radiation of heat toward the furniture and other combustibles and further toward the floor will tend to
propagate combustion. People in the room will get into a dangerous situation when flame grows andreaches the ceiling, and should escape from the place immediately. So as to provide an effective measureagainst spread of flame, it is generally recommended that ceilings made of combustibles should becovered with incombustible or quasi-incombustible materials or be coated with fire protection
coatings.
The interior finish restriction clauses of the Building Standard Law set restrictions on the use offinishing materials on the ceiling, wall, etc. of the room in terms of incombustible or flame retardant
property for the purpose of preventing spread of fire in the room and assuring time for people to escapefrom the place.
Fig7‐1 example of an assumption of heat release rate for theinterior finishings in room corner test

Heat release rate (kw)

Stop of test

Fig7‐2fire growth in a confined space

Hot gasgas layer
Hot
layer

Radiation

Time (sec.)

9Q8． In a fire involving polyurethane foams, to what degree will the room temperature rise?
A: As shown in Fig. 8.2, a fire of the building usually goes through the process of igniting →early firestage , fire growth →fully developed fire → ending stages. The room temperature rapidly rises in thefire grow stage, and, after the flashover, reaches as high as 1,0000C in fully developed fire in which thewhole room burns all over. The same is true with a fire involving polyurethane foams.

Fig8‐1 Change of temperature and gas concentrationin fire test of hotel room
FO(140sec.)

Figure8-2 Temperature, concentration profiles at a room firedark smoke filled in corridor

FlashoverInitial /developing stage

Fully developing stage

Delay

CO2 conc.

COconc.

Concentration (%)

Room temp.

O2 conc.

Room temperature （℃）

Ignition toceiling(146sec.)

Gas concentration (%)

Temperature（℃)

Emission of white smoke into corridor Fire fighting start( 378sec.)
Emission of dark smoke into corridor

TimeTime (min.)

Source: Fire Engineering Handbook, 3rd Ed. p.8 (1997)

Source： experiment report of hotel fire Osaka fire defense agency Feb. 1992

Q9． What should be done when flexible polyurethane foams catch fire?
A:

Water is most effective, so immediately pour plenty of water on fire of polyurethane foams. Of course

it is effective at an early stage of fire to use a home fire extinguisher (powder type) etc. Be sure, however,to add plenty of water on the extinguished fire to ensure complete extinction of any smoldering portion
that may be left inside. If you handle a large quantity of flexible polyurethane foams, immediately callthe Fire Department.

Q10． Will you give the ignitability of flexible polyurethane foams?
A:

The self ignition point of flexible polyurethane foam is about 4100C, which is nearly on a level withthat of cotton, newspaper, pine and other natural timbers, acryl, nylon and other synthetic fibers, andpolyethylene, polyvinyl chloride, polystyrene and other plastic materials. Flexible polyurethane products
will not undergo spontaneous combustion, and will have no hazard of becoming an ignition source. They
may be ignited, however, if exposed to high temperature of a lit cigarette, for example. There are
instances of welding sparks sticking to and spreading over flexible foams. Owing to the recently
advanced flame proofing technology, difficult-to-burn products are now available, but such products are
not perfectly free from burning if they are placed close to an ignition source.
From the viewpoint of safety design of buildings, the temperature at which a certain thing is threatenedwith catching fire from a fire source commonly present in ordinary architectural space is called its
ignition temperature. The ignition temperature is used to evaluate the ease of combustion of materials.

10

The higher are the critical heat flux for ignition and the thermal inertia of a material, rather than its
ignition temperature itself, the lower would its fire risk be. Foams generally have a lower thermal inertia
than solid resins, and, once ignited, tend to burn faster. Polyurethane foams, which do not haveparticularly short time to ignition compared with other materials, will be promoted to burn, due to low
inside cooling effect attributable to low thermal inertia, possibly up to deflagration. It is required tokeep ignition sources off polyurethane foams.
The thermal inertia : It contributes to thermal conductivity ×bulk density ×specific heat

Table10 ignition point and flash point of the variousorganic materials
Material

Ignition point（℃）

Flash point （℃）

Acryl textileー560

Nitrate cellulose

141

141

260

Acetic cellulose

305

475

200

ー

Nylon 6421

424

341-357

349

Nylon 66

ー

540

570

PC

467

580

Ignition point

Flash point

（℃）

（℃）

230-260

254

230

230

Pine

228-264

Wool
PE

CottonNewspaperPP（fiber）

Material

PP

ー

570

Phenol resin/glass
laminating board

520-540571-580

PTFE

ー

530

Melamine resin/ glass
laminating board

475-500

623-645346-399483-488

PVC

391

454

FRP

PS

345-360488-496

ABS

346

491

Rigid PU foam（ether
type）

310

416

280-300

450-462

Silicone resin/glass
laminating board

490-527550-564PS（foam beads
board）
PMMA

366

Test method ：ASTM D1929
Source: C,J.Hilado；Flammability Handbook for plastics,1969(Technolic Pub)

Fig10-1 Ignition temperature of the various plastic materials

11

Fig10-2 Ignition time of Polyurethane foam

Fig10-3 Ignition characteristics of the various materials
Higher ignition temperature○ Wood type material◆ Plastic material△ Plaster board○ Carpet

Urethane
foam

Steep＝

Acryl sheet

Incidence heat quantity

PC

PIR

Ignition limit heat flux

Ignition time

Square root of the reciprocalof ignition time

Steep＝

PUR
foam

PUF◆
foam

PU
foam
Not easy to get warm

Product of thermal inertia and risingvalue of ignition limit heat flux

Source：mechanism of building fire and fire safety design BCJ

Source：mechanism of building fire and fire safety design BCJ

Q11． Will you give the flash point, ignition point and oxygen index of flexible polyurethane foams?
A:

All of them vary with the constituent materials and the test methods used. Table 11 shows

measurements of the ignition point and the oxygen index of flexible polyurethane foams. JUII
determines the ignition point of flexible polyurethane foams pursuant to ASTM D1929, and haveobtained measurements of 350-3900C. Materials with the oxygen index of 21 or less are generallyclassified as combustibles.

Fig 11

Ignition temperature of various materials

Source：ISOPA “performance of polyurethane building products in fires

Table 11 Material Ignition Temperaturematerial

LOI

Min. piloted
ignition tem.(℃）

Min. non-piloted
ignition tem.(℃Melamine paper laminate
standard

29.5

398

433

Natural rubber latex
adhesive

19.8

289

330

Epoxy resin

20.9

315

429

Flexible PVC foam

25.6

441

441

Natural rubber latex foam

17.3

274

310

Flexible polyurethane foam

18.1

335

335

Polypropylene

17.5

342

364

ANSI/ASTM D1929
Department of diffence materials research laboratories 、 commonwealth of Australia

12Q12． Will flexible polyurethane foam products combust spontaneously?
A: Polyurethane foam products will not undergo spontaneous combustion.
However, it should be noted that the sun’s rays focused with a lens or any other thing exerting a lenseffect may ignite them. Since flexible polyurethane foam is a heat accumulative material, it may begin
to burn if continuously exposed to a focused beam of light for a long time. The self ignition point of aflexible foam (an example cited here is an ordinary flex-foam not treated with flame retardant ) is
4560C.

Q13． Is the combustion rate of flexible polyurethane foams faster than other materials?
A: The ease of combustion of a material used to be generally determined by measuring its combustion
rate based on its mass reduction, but now it is getting to be determined by the heat release from theburning object. The total heat release from burning flexible polyurethane foams in terms of the mass
reduction and the heat release is not high compared with other materials, but the heat release rate isdifferent with different constituents.
Adding flame retardant to the foam or covering the foam with cover material is an effective means toslow the mass reduction or heat release, but cannot stop its combustion. Sufficient ignition prevention
and fire fighting measures are required.
In the United States the fire growth rate of combustibles is classified as ‘ultra fast’ (α＝0.2ｋｗ/S2 ), ‘fast’(0.05), ‘medium’(0.015) and ‘slow’(0.00313). According to this classification, large cushioned furnituresuch as sofa falls under ‘ultra fast’; ordinary furniture ‘fast’; and goods or products covered withincombustible material ‘medium’ or ‘slow’.
Taｂle13-1 Burning rate of the mattress made of theflexible polyurethane foamMaterial

M aximumBurning rate
max
（ｇ/sec)Burningmass
By load cell（g）

Peak heatrelease value(K J/g)Total heatrelease value(KJ/g)

Mattress１

7．03

1744

25．3

27．3

Mattress３

5．25

1833

23．1

24．7

Mattress４

13．52

1572

21．9

23．3

Mattress５

4．52

1735

20．3

20．2

Mattress６

4．87

1500

23．2

23．3

Source:Lecture m eeting paper of Architectural Ｉnstitute of Japan ｐ13－ 14 Aug. 200713

Heat release rate of the various storage combustibles (closed space)

Total heat release valueof mattress by lengthwise

heat release valueof mattress by lateral

Heat release rate of sofa

Heat release rateof mattress by lateral

Total heat release
rate of TV
Total heat release
rate of sofa
Heat release
rate of TV

Time （min.)Time （min.)Fig13-2 Standard Fire Growth Rate Curves.
(with some examples of fire test fuels)

Time from ignition (sec)
Source：National Fire Protection Association、National Fire codes, NFPA92B,Figure C.2 ( c )Table13-2 ”t-squired” Fire Growth Rates
Classification of
Growth Rate

Heat release rateof sideboard

Ultra Fast

Time to reach 1050kw(seconds)
75

Fast

150

Medium

300

Slow

600

14

Total heat release
rate of sideboard

Total heat release value( MJ）

Burning endpoint

Heat release rate （kW）

Heat release rateof mattress by lengthwise

Total heat release value( MJ）

Heat release rate （kW）

Fig 13-1

Table 13-3

Result of measurement of heat release rate for each materials（full size test）

Test method according to ASTM E1354

Foil only

Steel Frame

Insulatd

SpecimenFrame
Tig (s)Q” pk

Tig (s)Q” 1802(KW/m )

2Q” 180

Q” pk
2(KW/m )

(KW/m )

Tig (s)2

Q” pk

Q” 1802(KW/m )

(KW/m )

(KW/
m2)

PMMA

23

827

630

24

920

524

24

994

637

25

304

176

25

239

144

24

288

171

25

248

154

27

198

126

21

233

159

35

579

179

45

388

188

39

475

188

6

83

54

34

67

27

9

74

34

3

801

193

2

453

191

5

675

192

16

323

235

19

258

192

18

302

232

47

552

443

58

414

316

56

531

427

Density=1160 (kg/m3)
T=25mmParticle board
3

Density=640 (kg/m )T=12-13mm
Oak wood blocks
3

Density=735 (kg/m )T=32mmExtruded PS foam
3

Density=50 (kg/m )T=26mmPolyisocyanurate foam
3

Density=28 (kg/m )T=45mmFlexible polyurethanefoam
Density=23 (kg/m3)
T=50mmPVC
3

Density=1340(kg/m )
T=6mm
PE
3

Density=1090 (kg/m )T=6mm
Source: Journal of Material,

Vol 17, No 2, p51-63, Apr. 1993

15

Fig13-3 Flexible polyurethane foam

Fig13-5

Polystyrene

Fig13-4 Rigid polyurethane foam

foam

Fig13-6

Oak wood blocks

Source: Vinyl Institute, a Division OF the society of the plastics Industry, Inc.
* Refer to CPI and PFA documents

Q14． It is told that plastic materials emit much smoke when burned. How about polyurethane foams?
A:

The quantity of smoke differs considerably with the constituents and shape of the material on fire, andthe temperature, oxygen concentration and other ambient conditions. Measurement results do notindicate that the polyurethane foam emits more smoke than other materials (measured at 550 and 8500C).
Table1 4

S m oke density of th e v arious plastics

Combustion
temperature

550℃

850℃

Smoke
concentration

Smoke
coefficient

Smoke
concentration

Smoke
coefficient

Plastic typem3

C･ m 3 /gm3

C･ m 3 /g

Polyurethane
foam

0.284

0.710

0.182

0.173

PVC

2.025

0.854

2.062

0.793

PC

0.746

0.386

1.362

0.605

PS foam

0.131

0.815

0.450

0.461

ABS resin

1.640

0.811

1.225

0.569

PE

0.607

0.331

0.550

0.289

PP

0.595

0.457

0.532

0.360

Source: M odern Plastics 119, July 1983

16

Q15． Do flexible polyurethane foams catch fire easily?
A: The ignition point of organic materials generally ranges from 230 to 3900C and the self ignition point
ranges from 230 to 5300C. The flash ignition point and the self ignition point of flexible polyurethane
foam (the specimens used here are ordinary flex-foams not treated with flame retardant ) are 2880 and
4560C, respectively, which are nearly commensurate with those of cotton, newspaper, pine and othernatural timbers, acryl, nylon and other synthetic fibers, and polyethylene, polyvinyl chloride, polystyrene
foams and other plastic materials. Like all these materials, flexible polyurethane foams are immune tospontaneous combustion.
Foams generally have a lower thermal inertia than solid resins, and, once ignited, tend to burn faster.
Polyurethane foams, which do not have particularly short time to ignition compared with other materials,
will be promoted to burn, due to low inside cooling effect attributable to low thermal inertia, possibly up
to a phenomenon of deflagration. It is required to keep ignition sources off polyurethane foams.

Q16． What is the degree of the heat resistance of flexible polyurethane foams?
A:

The heat resistance of flexible polyurethane foams varies with the type of foams. The foams cangenerally be used in a temperature range up to 800C. The strength of foams is reduced to half duringcontinuous use of 500-700 days at 800C. There will be no heat resistance problems in ordinary use.
Q17． Won’t flexible polyurethane foams ignite by sparks of static charges built up in them?
A: Static charges generate anywhere in any place including production facilities, construction sites anddwelling houses.
Flexible polyurethane foams, which have a low electric conductivity, easily build up static charges byfriction, but such static charges will have a low probability of igniting polyurethane foams because ofvery low discharge energy, that is, ignition energy.
However, when polyurethane foams are being bonded using an adhesive that contains a flammablesolvent, or if polyurethane foams containing flammable liquid are present at the job site, it should be
noted that flammable vapors may be set to fire by spark discharge, which in turn may ignite the foams.
In cutting foams, proper measures should be taken to prevent static ignition risk of foam dust.

E x a m p l e o f e l e c t r ic a l c h a r g e t h e v a r io u s m a t e r ia ls
各 物 質 の 帯 電 例

17

オ
｜
ロ
ン

サ
ラ
ン

ポ
リ
ウ
レ
タ
ン

ポ
リ
エ
チ
レ
ン

ポ
リ
プ
ロ
ピ
レ
ン

塩
化
ビ
ニ
｜
ル

シ
リ
コ
ン

テ
フ
ロ
ン

Teflon

セ
ル
ロ
イ
ド

PVC

ポ
リ
エ
ス
テ
ル

Silicon

ア
セ
テ
｜
ト
・
レ
｜
ヨ
ン

Polyethylene

真
鍮
・
銀

Polypropylene

ニ
ッ
ケ
ル
・
銅

Saran

硬
質
ラ
バ
｜

Polyurethane

ス
チ
｜
ル

Celluloid
Orlon

紙

Polyester

ア
ル
ミ
ニ
ウ
ム

Brass・silver

ウ
｜
ル

Eマ
a s イy ナ
t o スb eに e帯
le c電t rしi fyや nすe gいa t iv e ly
Acetate・rayon

ナ
イ
ロ
ン

Nickel・Copper

雲
母

Wool
Aluminum
Paper
Steel
Rigid rubber

ガ
ラ
ス

Nylon

Asbestos

ア
ス
ベ
ス
ト

Glass
Mica

プ aラs yス tにす いp o s it i v e lyEo b帯e 電e leしcやt r ify

Q18． Can flexible polyurethane foams be made fire retardant?
A: Flexible polyurethane foams can be made fire retardant by selection of the structure of the product andthe type of constituents used, and by addition of fire retardant. Foams having the following fire retardant
characteristics per application are commercially available:
・Hard to ignite,
・Ignitable; after ignition, fire is slow in spreading (that is, the combustion rate is low), and・Ignitable; after ignition, fire goes out spontaneously when the fire source (a match or the like) isremoved.
The fire retardancy of flexible polyurethane foams is generally evaluated by igniting a specimen using asmall fire source such as cigarette, match or methenamine and measuring how soon the fire goes out
spontaneously when it is removed. With respect to furniture, bedding and other products composed of aflexible polyurethane core covered with other materials, the fire retardancy of the product differs with thematerials of the cover used. In Europe and the US, the fire retardancy of furniture and bedding isevaluated in full size test.（See Q33 andQ34）

Q19． Do flexible polyurethane foams differ in combustibility from plastic foams used as building
interior materials?
A:

Rigid polyurethane foams used as building materials are fire retardant, and isocyanurate foams which

exhibit higher fire retardancy are also used. Rigid polyurethane foams are composed of closed cells
which contribute to thermal insulation performance. In contrast, the cells of flexible polyurethane foams
are so structured as to allow air ingress, and this makes a difference in combustibility of the materials.

Q20． Do flexible polyurethane foams for upholstery application differ in combustibility from otherplastic foams?
A: Flexible polyurethane foams for upholstery applications are used in mattresses, pillows, carpet
backing, sofa padding, backrests, chair cushions, ‘kotatsu’ mats, floor cushions, dishwashing sponges,
doll stuffing, diapers, bath mats, ironing board covers, clothes brushes and other products. The
combustibility of these flexible foams is quite similar to that of other plastic foams.
Ref: ISO 871：2006--Flash and Fire Points of Plastics

Q21． When flexible polyurethane foams burn, what gases will be emitted?
A:

The fire of polyurethane foams is basically not different from ordinary fires. Just like other organic

materials, burning polyurethane foams emit mainly carbon dioxide, carbon monoxide and moisture vapor.
Other trace gases vary with the combustion conditions such as temperature and air supply during thecourse of fire. Shown in the following are combustion gases emitted by various materials measured in18small experiment equipment, but it is generally considered that gas components found in a small
experiment would not represent all the gases emitted in actual fires. Literature lists varying
measurements of gas components in varying combustion conditions (temperature and air supply), andmentions carbon dioxide and carbon monoxide as main combustion gas components, together withcombustible hydrocarbons and nitrogen compounds produced by thermal decomposition.

Table21-1 combustion products of polyurethane foamCombustion gas mg/sample 1g
LiteratureA

Literature
B

Literature
C *1

Literature D

700

500

800

350

Combustion
condition℃

Air supply

L/hr

100

13.2

L/min

(1.7)

0.22

4.0

4.0

4.0

CO2

666

88

320

264

644

1236

CO

173

57

970

26

138

353

HCN

3.3

<2

8

1

6

8

Methane21

4.6

Ethylene43

3.9

Acetylene

14

Combustion
gas

750

120

Ethane1.3

Propylene

29

Butene0.38

Acetaldehyde

32

Acetone13*1: in 5l flask

Source: Fire Engineering Handbook, 3rd Ed. (1997)

Table21-2

500

Combustion gases from polyurethane foam

TesterMorimoto １）

combustion
condition

700℃

Kishiya 、Nakamura3）

Sumi、Tsuchiya 2）

350℃ 500℃

800℃ in 5l flask

700℃

1.7
L/min

0.8
L/min

0.4ｇ

0.6ｇ

1.2ｇ

1.6ｇ

2.0ｇ

2.4ｇ

4 L/min

CO2

0.666

0.625

1.4

0.7

0.47

0.43

0.32

0.28

0.264

0.644

1.236

CO

0.173

0.16

0.2

0.23

0.157

0.142

0.97

0.092 0.026

0.138

0.353

HCN

0.0033 0.001

0.008

0.008

0.008

0.008

0.008

0.008 0.001

0.006

0.008

CH4

0.021

0.017

C2H4

0.043

0.037

C2H2

0.014

0.0064

0.12

0.13

0.12

0.12

0.12

0.10

Source ： 1） High polymer Vol 22, No253, p190-195 , 1973
2) J.fire and flamm, 4, p15-, 1973
3） Plastic 25(11) 1974

19

Table 21-3 Combustion test products (mg/g)
Fire Product

CEL*1

PES*2

Silk

Wool

Nylon

PAN*3

PU
foam

PE*4

PP*5

PMMA*6

PVC*7

CO2

202

290

170

69

35

73

88

120

21

99

<8

CO

88

85

13

21

13

12

57

120

25

61

7.0

HCl

-

-

-

-

-

-

-

-

-

-

230

NH3

-

-

21

12

6

2.6

-

-

-

-

-

HCN

-

-

1.3

1.8

-

6.6

<2

-

-

-

-

COS

-

-

-

1.8

-

-

-

-

-

-

-

CH4

2.4

1.7

1.7

1.9

0.84

3.4

4.6

2.5

1.5

0.56

1.7

C2H4,C2H2

2.8

2.7

0.57

1.6

3.6

0.6

3.9

18

2.1

0.51

0.98

C2H6

0.52

0.14

0.62

0.91

0.92

0.79

1.3

1.6

3.1

0.08

1.7

C3H6

0.88

0.18

0.6

2.0

2.6

0.27

29

12

27

1.23

0.73

C3H8

0.11

-

-

1.3

0.7

1.4

-

2.5

-

-

0.83

C4H8

-

-

-

1.1

2.9

-

0.38

-

4.8

-

-

C6H6

-

2.7

-

-

-

-

-

-

-

-

11

C6H5CH3

-

0.23

-

-

-

-

-

-

-

-

-

CH3OH

-

-

-

-

0.68

2.0

-

6.2

5.6

-

-

CH3CHO

2.5

14

-

-

0.81

-

32

10

7.9

-

0.3

CH2=CHCHO

2.1

-

-

-

-

-

-

8.4

3.9

-

-

CH3COCH3

-

-

-

-

-

-

13

-

-

-

-

CH3CN

-

-

5.7

1.6

1.2

3.0

-

-

-

-

-

CH2=CHCN

-

-

-

0.83

-

5.6

-

-

-

-

-

MMA*8

-

-

-

-

-

-

-

-

-

89

-

Residue

4.1

9.1

19.3

12.7

4.3

19.5

4.3

32.3

4.0

0

15.5

*1.Cellulose *2.Polyester *3.Polyacrylonitrile*6.Polymethylmethacrylate*4.Polyethylene *5.Polypropylene*7.Polyvinylchloride *8.Methymethacrylate

Decomposition temperature；500℃, O2 concentration；21%, Air flow；0.22ml/min.
Decomposition time；4min. Sample weight；100 mg

20

Table21-4 Combustion gases from high polymers
Specimen（0.1g）

Air
supply（L/h)

PE

Combustion gas （mg/ specimen1ｇ）
HCL

CH4

C2H4

C2H2

Gas
rate
％

210
195

72
65

185
187

34
9.5

６２．５
51.2

619
590

178
207

6.5
6.5

18
16

13
6.4

３０
29.7

657
594

177
207

6.5

2.3

11
6.4

69.3
６８．８

CO2

CO

100
50

738
502

PS

100
50

PVC

100
50

286
279

COS

SO2

N2０

NH3

HCN

Nylon66

100
50

590
563

206
194

9.8
3.5

31
26

40
39

94
82

15
7.4

60.7
55.7

Polyacrylic
amide

100
50

796
738

157
173

17
32

18
21

16
20

10
13

8.5
4.2

63.3
６２．１

Polyacryliro
nitril （PAN)

100
50

556
630

108
132

56
59

5.9
7.8

7.4
4.2

37.7
42.7

Polyurethane（PES/TDI type）

100
50

666
625

173
160

3.3
1.1

21
17

14
6.4

51.4
44.5

PPS

100
50

1796
1892

161
219

2.1
1.1

85.1
92.7

Epoxy resin

100
50

1136
961

153
228

2.2
3.3

7.4
6.4

52.9
52.7

Urea resin

100
50

1193
980

80

22

96.7
92.5

100
50

576
702

194
190

96
59

81.8
86.8

Melamine resin

2.5
2.5

43
37

423
451

34
27

84
136

16
33

2.3
4.6

Q22． If gas or smoke emitted by flexible polyurethane foams on fire is inhaled, what influences will
occur to the body of the inhaler and what measures should be taken?
Gas or smoke inhaled first irritates the throat. If inhaled in abundance, it is generally assumedA:

that it causes headache and some symptoms that resemble those of carbon monoxide intoxicationsuch as difficulty of moving, and disturbances of perception and thinking. The first thing to dowhen gas or smoke is inhaled is to breathe in fresh air and lie quietly. If the symptoms are grave,
consult a doctor promptly.
Much remains unknown as to how such disturbances develop when a person breathes gases
emitted by fire, as well as how such poisonous gases are produced and in what conditions suchgases are exposed to human bodies.

*

The subjective symptom appears to become 10% or more, and the lethal concentration is assumed to be
60～70% when depending on the CO-Hb concentration in blood in principle, though the poisoning
symptom is controlled by the inhalation concentration of the carbon monoxide, the exposure time, andthebreathing state, the amount of circulating blood, and the hemoglobin content in blood etc. whenbloody mesne of breath.

21

Table22 Symptoms associated with a given
concentration of COHb
Carboxyhemoglobin(COHb)

Symptoms～10％

No symptoms

10～20 %

Mild headache、expansion of skin blood vessel

20～30%Headache, nausea, vomiting, and trouble making decisions

30～40％

Dizziness, muscle weakness, vision problems, confusion, and increased
heart rate and breathing rate

40～50％

Dizziness, muscle weakness, vision problems, confusion, and increased
heart rate and breathing rate

50 ～60％Loss of consciousness、coma, cheyne-stokes breathing, sometime death60～70％

Loss of consciousness、coma, cheyne-stokes breathing, breath weakening, sometime death70％～

Breathing stop, circulation lethargy, death

http://biology.about.com/od/molecularbiology/a/carbon_monoxide.htm

Q23． When flexible polyurethane foams are set on fire, what is the amount of smoke emission
compared with other plastic materials?
A:

The amount of smoke emission differs considerably with the constituents and shape of the material onfire, and the temperature, oxygen concentration and other ambient conditions. Polyurethane foams will
not emit more smoke compared with other plastics.
Safety measures against smoke are said to be one of the most important items in fires of organic
materials. Exposure to smoke is a great menace to the safety of people.
The Fire Service White Paper mentions that failure to escape in fires occupies a high rank in the list of
the causes of death. Smoke emission will induce loss of visual field, smoke inhalation, impaired
judgment, reduced ability to take action and psychological impact, possibly leading to failure to escapeand death. Firefighting in the earliest stage is badly needed.

Table23‐1

Smoke density of the various plastics

Combustion
temperature

550℃

850℃

Smoke
concentration

Smoke
coefficient

Smoke
concentration

Smoke
coefficient

Plastic typem3

C･ m3/gm3

C･ m3/g

Polyurethane
foam

0.284

0.710

0.182

0.173

PVC

2.025

0.854

2.062

0.793

PC

0.746

0.386

1.362

0.605

PS foam

0.131

0.815

0.450

0.461

ABS resin

1.640

0.811

1.225

0.569

PE

0.607

0.331

0.550

0.289

PP

0.595

0.457

0.532

0.360

Source: Modern Plastics 119, July 1983

22

Q24． What sort of products are ‘low-combustibility’ polyurethane foams?
A:

Flexible polyurethane foams, which are organic materials just like other plastics, are subject to

combustion (classified as combustibles in the Fire Service Law).
Low-combustibility foams are such products as have been made flame resistant by various means, andgenerally have the following characteristics:
・Hard to ignite,
・Ignitable; after ignition, fire is slow in spreading (that is, the combustion rate is low), or
・Ignitable; after ignition, fire goes out spontaneously when the fire source (a match or the like) isremoved.
What are called low-combustibility polyurethane foams are those products that are judged to havesufficiently low combustibility in tests made per application, and may have different ratings for different
applications
The fire retardancy (also called combustion resistance or flame resistance) of polyurethane foams andother plastic materials, which are organic compounds, is quite different from the fire resistance ofconcrete and steel. Polyurethane foams are threatened with burning if exposed to flame for a long time.
‘Low combustibility’ indicates the degree of flame intensity and the extent of exposure time that thefoams can withstand.

Q25． Do combustion gases of flexible polyurethane foams contain toxic constituents?
A:

All combustibles, whether they are natural materials or synthetic materials, will, while burning, emit

toxic gases of some kind. Main toxic gases that have been identified are carbon dioxide (CO2), carbon
monoxide (CO), and nitrogen compounds such as hydrogen cyanide (HCN) and nitrogen oxides (NOx).
Polyurethanes will produce trace amounts of some additional compounds.
There is misunderstanding that smoke emitted in a fire that involves polyurethane goods implicitly has
a higher health hazard than in a fire of other synthetic resin materials or natural materials because theformer contains hydrogen cyanide gas. Hydrogen cyanide gas is produced in fires involving any
nitrogen-compound-containing materials (wool, acryl, nylon and ABS, for example).
Flexible polyurethane foams, which contain nitrogen compounds, emit cyanide gas, depending on the
combustion conditions, but it is not on the high side, as shown in the following tables. It is reported
that carbon monoxide is the most hazardous gas, in terms of toxicity, in every combustion condition of
fire.

23

Table 25‐１ Combustion products of organic materials＊１(mg/sample1g)
Material

NH3

CO2

CO

HCN

PU foam＊2

666

173

3.3

Polyethylene

738

210

291

Polystyrene

619

178

37.5

Polyvinylchloride

657

177

Nylone 66

590

205

31

9.8

149

Polyacrylamide

796

157

18

17

34.5

Polyacrylnitri

556

108

56

13.3

Epoxy resin

1138

153

2.2

25.7

Cedar

1573

16

HCL

Other
hydro-carbons
78

286

11

＊１ Combustion parameters： temperature 700℃、air flow 100l/hr＊2. Polyester polyurethane (from TDI)

Table 25‐2 Generation of HCN at combustion of N-containing
materials
HCN peak conc. ppm

Peak temp. ℃

Nylon

328 – 520

485 – 429

Wool

368

567

Polyacrylonitrile

445

381

Urea formaldehyde
resin
Rigid PU foam

458

321

321 －467

587 － 549

Flexible PU foam

181

388

Material

F.M. Esposito et al., Journal of Fire Sciences, 6, 195-242 (1988)

Q26． What gases will be emitted during smoldering?
A:

Main gases emitted during smoldering (for example, when a ‘futon’ ignited by a lit cigarette issmoldering), are carbon dioxide and carbon monoxide, and they are produced in abundance. Thus carbon
monoxide is generally the greatest cause of danger. Depending on the constituents of smoldering
materials, a variety of slight amounts of thermal decompositions will also be produced, such as low
molecular hydrocarbons, hydrogen chloride, nitrogen oxides and a trace amount of hydrogen cyanide(HCN).
It is said that organic substances containing nitrogen would hardly emit acrolein or formaldehyde.
The temperature at the incipient and growing stages of fire is 400-7000C, and, when the materials areflamed, gases emitted by oxidizing flame at such temperature are mostly carbon dioxide and water vapor.
The amount of carbon monoxide and irritant gases are relatively small, but as the fire grows, emission of24

toxic gases including carbon monoxide will increase. The temperature at the blazing and ending stages offire exceeds 8000C. As oxygen concentration is low at such high temperature, thermal decomposition
products will be low molecular and form carbon monoxide and other toxic gases. As the concentrationsof these gases increase, they will be more dangerous.
Fig26‐1 Toxicity of smoke during Chair smoldering tests for
Polyurethane foam

Source: Fundamental and Applied

Toxicology 3 :619-626 (1983)

Fig26-3

Fig26-2 VOC concentrations ｖersus time at the ceiling

Concentrations of inorganic gases Vs time at theceiling

Source: 12th International Conference on Fire and Materials, San Francisco， CA January 26-28,2009 p12
Source: 12th

International Conference on Fire and Materials, San Francisco， CA January 26-28,2009 p12

Source: 12th International Conference on Fire and Materials, San Francisco， CA January 26-28, 2009p12

Q27． What are typical combustion tests of flexible polyurethane foams?
A:

There are combustion tests specified for automobiles, railroad cars, aircraft seats, furniture and otherapplications. The following table lists the specification numbers and designations of such tests.

25

Table27-1 combustion test for flexible polyurethane foam
Regulation No

Title

Category

FMVSS
No302

United States car safety standard

Lower
combustibility

Remar
k

Flame resistive standard of the Ministryof Transport for car interior material
UL-94

Standard by which combustibility degreeof material is recognizedLower
combustibility

A-A standard

Material combustion examination for
railway vehicle

Lower
combustibility

Flame retardant performance test
standard for bedding such as mattress

Lower
combustibility

FAR25.853

air-proof examination points

Lower
combustibility

UL900 class2

National Fire Protection Association
No.90A and No.90B

Lower
combustibility

California law 117

Lower
combustibility

HF etc.

Reference
Flexible foam

BS4735(UK), ＵＬ94‐HF1 (USA), CSE-RF4(Italy), BS5852 crib5,
consumer safety law in 1988, California law 117

Foam for car

FMVSS-302

Rigid foam

Performance required in BS476 part6, 7 , NFP92-501(France),
DIN-4102(Germany)

Q28． Can we find the combustibility of polyurethane foams by simple means?
A:

There may be cases in which the combustibility of foam materials under MVSS or UL Standards isroughly estimated by heating pieces of foam with a lighter or match, but such a simple means will not begood enough as a method for determining whether such foams conform to such standards or for making
comparisons of fire retardant foams conforming to MVSS or UL Standards with each other.
The reason is that, if a small fire source like a lighter is used, polyurethane foams will not always exhibit
the same burning behavior as under UL or other standards in which a heat source of high calorific value(gas burner) is used.
In addition, there are presently no simple means to properly evaluate a number of combustibility
characteristics such as ignitability, smoke emission, heat release and combustion rate.
Understanding the burning behavior of combustibles in the incipient stage of fire is important in
preparing fire safety design.
The combustion of polyurethane matting is divided into the melting of the material occurring

26

immediately after ignition and the burning of vapors arising simultaneously. There is an example ofsimplified
modeling that is proposed to predict, by use of small cubic specimens, the heat release rate of urethane
foam based on such data as the growth rate of the radius of melting, the rate of the growth of residue andthe rate of heat release in terms of oxygen consumption.

Heat release rate Q(kw）

Fig28 Model vs Experiment in comparison

Time t （sec)
Source:Lecture meeting paper of Architectural Ｉnstitute of Japan、 Aug. 2002
“simple forecating method of heat release rate for urethane mat”

Q29． What materials fall within the interior finishing certified by test under the Building Standard
Law?
A: Commonly used interior finishes are wood, plastic, wall covering and gypsum board materials.
Buildings subject to the regulations and restrictions on interior finishes are designated buildings andlarge wooden buildings, and portions of those buildings subject to such restrictions are walls and ceilings(or roofs, if the building has no ceilings). Incombustible, quasi-incombustible or fire retardant materials
must be used as interior finishes in such portions of such buildings. Presently no flexible polyurethane
foams fall within this category.
Note: Buildings free from such restrictions are “houses that meet the prescribed conditions of building
structure and total floor space.”
Depending on the use and the construction, buildings are generally subject to legally prescribed
restrictions on the structure and the room and corridor interior finishes. The purpose of such restrictions
is to hold back the danger in fire by using fireproof materials. Required fireproofness of interior finishingdiffers with the use, the structure and the floor space of the building, and is certified by tests
conducted under the law so that the interior will be finished with “fire retardant or better,”“quasi-incombustible or better,” or “incombustible” materials. These interior finishing materials areapproved by the Ministry of Land, Infrastructure ,Transport and Tourism.

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Q30． What does ‘interior finish restriction’ signify?
A:

There are restrictions on materials used for interior finishing, depending on the use and the scale ofthe building (Ref. Table 31). Such restrictions are prescribed by the Building Standard Law so as toprevent fierce combustion of interior materials leading to fast growth of fire, emission of toxic gases andjeopardizing escape of people.
The danger of indoor fire comes from a flashover in particular, which is a phenomenon of

instantaneous combustion of the whole room by heat accumulated in it. The purpose of the restrictions
on interior finishes is to hold back ignition of the interior finishes and control occurrence of a dangerous
flashover so that people inside may have an escape.
The Building Standard Law imposes interior finishing restrictions on houses, designated buildingssuch as theaters, clubhouses, hospitals, hotels and other public buildings, buildings of three or morestories or with a total area exceeding 1,000m2, buildings that have a room without windows or similar
openings, and buildings equipped with a kitchen or other equipment that uses fire. It is required toconstruct these buildings so that the standards of interior finish restrictions (Article 35-2 of the BuildingStandard Law and from Article 128-3, Paragraph 2 to Article 129 of the Enforcement Ordinance of the
Building Standard Law) will be met by using such heat insulating materials as are designated asincombustibles or quasi-incombustibles or by covering the surface of heat insulating materials withlegally approved incombustibles.
・Applicable laws and regulations: Article 35-2 of the Building Standard Law, and from Article
128-3, Paragraph 2 to Article 129 of the Enforcement Ordinance of the Building Standard Law

Article 35-2 (Interior Finishes of Designated Buildings, Etc.) of the Building Standard Law prescribes
restriction of interior finishing materials per use and scale of the building so that the growth of fire
may be held back and escape and firefighting activities may be facilitated. As prescribed by theprovision, the restriction applies to the portions of walls and ceilings facing the rooms.
Reference: Article 35-2 (Interior Finishing of Designated Buildings, Etc.) of the Building Standard
Law: “Except as prescribed by government ordinance, buildings for uses designated in Column A of
Exhibit 1, buildings of three or more stories, buildings that have a room without windows or similar
openings designated by government ordinance, buildings with a total area exceeding 1,000m2 , andbuildings with a kitchen, bathroom or other rooms equipped with a stove, cooking range or otherequipment that uses fire shall have the portions of walls and ceilings (or roofs, if the building has no
ceiling) that face any room finished as per the technical standards prescribed by government ordinanceso that hindrance or obstruction to the prevention and control of fire will not arise.”28

Q31． Are flexible polyurethane foams regulated by the interior finishing restriction?
A: Since flexible polyurethane foams are not used as interior finishing, they are usually not subject to theinterior finishing restriction under the Building Standard Law. However, furniture and other things
placed in buildings are regulated by the flame retardant standards stipulated under the Fire Service Law.
Commonly used are flame retardant products certified by the Flame Retardant Products Certification
Committee as per the performance test standards authorized by the Japan Flame Retardant Association.
For example, the fire retardancy of flexible polyurethane foams used in bedding is evaluated by 450
methenamine method
Ref: Q31A Table 31: Tabulated List of Interior Finish Restriction

Q32． Does the Fire Service Law regulate the interior materials?
A: The Fire Service Law prescribes measures for prevention and control of fire of interior goods andproducts. The intention of the Law is to ensure prevention of fire, firefighting at the earliest stage,
rescue of people and extinction of fire, and to provide full fire protection by making proper use of
firefighting equipment under good fire control practice. With the aim of protecting people from fire
exposure, the Law specifies objects of fire retardancy regulation and prescribes restriction of fire
retardant goods and products for use for such objects.
In particular, definite fire safety measures are required for public buildings provided for use by many
unspecified persons.
The laws governing the matters regarding the fire prevention of interior materials, products and goods
are the Building Standard Law and the Fire Service Law. The Building Standard Law prescribes
restriction on interior finishing with intent to ensure safety and escape of people. The Fire Service Law
requires fire safety measures which will work synergistically with the relevant provisions of the
Building Standard Law for the achievement of safety of people and protection of property up to acertain level.

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Table32 Interior finishing restriction of Building Standard Law and Fire
Service Law
Name of material

Fire prevention material

Flame retardant product

Performancestandard･Noncombustible materials･Quasi noncombustible
materials･Fire retardant materials

Flame retardant performance (Numericalvalues of after flame, after glow, charring
length,and the area, etc. by each plywood ,athin cloth, thick cloths, and the carpets etc,
have been decided).

Object building ofmaterial

Special building etc( See the list of Interior
finishing restriction)

Fire prevention object (See fire prevention
object given flame retardation regulation)

ObjectPart that faces room of walland ceiling

Carpet such as rug , curtains, black
curtains, blind made of cloth, plywood usedon stage setting at the scene, plywood for
exhibitions or sheet for construction

Law, Cabinet
order･Building standard law･Order for enforcement ofbuilding standard law･Regulation for enforcement ofbuilding standard law･Fire service law･Order for enforcement of fire service law

Ministry of Land,
Infrastructure、Transport andTourism･Ministry of internal Affairs andcommunications (MIC)
・Fire and Disaster Management Agency

Department
concerned･Regulation for enforcement of building
standard law

Q33． Are there any differences in the combustion test of interior materials in Japan and in foreigncountries?
A: Yes. Different concepts of expected fires make differences in the combustion tests in Japan and in
America and Europe. Test and evaluation methods of interior products and goods for use in houses differ
accordingly, and the test of bedding in particular is conducted by different methods in different countries.
In Japan the flame retardancy performance of household interior products and goods is evaluated insmall tests using small fire sources in accordance with the pertinent provisions of the Fire Service Law
and the pertinent clauses of the standard of Japan flame Retardant Association. In the UK the flame
retardancy test is conducted as per BS5852 using different fire sources (seven kinds of fire sources) withdifferent uses of the products. In the US a number of test standards for furniture including Cal TB117,
TB129, TB133, ASTM1590 and CFR1663 are used, depending on the required fire retardancy
performance, the use of the products and the scale of the tests conducted.

Q34． What care is required to prevent fire?
A: There are a number of instances of fire in houses and vehicles in which flexible polyurethane foams
used in sofas, mattresses and seats burned, but polyurethane foams have scarcely been the cause of fire.
Most common cause of house fire except arson is careless handling of lit cigarettes. Never smoke
while lying on sofa, mattress, bed or ‘futon,’ and keep naked flame off these things.
Use of flame retardant mattresses, curtains and other goods that satisfy the requirements of the30

Qualification Guideline of the Japan Fire Retardant Association is recommended. The surface ofvehicle seats is covered with materials that provide MVSS conforming products.

Fig34-1 Death toll of housing fire by Ignition material in 2008
( except arson/suicide）
cigarette
20%

unknown, other46%

Death of housing fire
1148 persons

stove
12%

cooking stove8%
kotatsu
1%
candle,lamp
3%match, lighter
5%electricalappliance
5%

Source： fire white paper in 200831

Q35. What educational activities for fire prevention is JUII engaged in?
A:

In ordinary houses flexible polyurethane foams scarcely become the cause of fire, but arson or wrong

use of fire may lead to fire of the building. For the purpose of preventing such fire, we publish and utilize
fire prevention booklets and contribute educational articles to trade journals.

Table35

Documents for fire prevention and fire safety

Reference

Title

1

Publisher

Guidance of safety handling of rigid

・Japan urethane insulation instituteurethane foam July, 1995

・Guidance : Tokyo Fire Department
Multilingual

2

Let’s prevent a urethane fire.

・Building Contractors Society Construction
departmental Meeting urethane measures task
force

3

Guidance of the fire prevention in

・Japan Construction Occupational Safety andconstruction site with plastic foam

Health Association

thermal insulation

4

Flame resistive grade 3 simplified

・Japan Urethane Industry Instituteconfirmation test method of rigid sprayurethane foam

5

Guidance of polyurethane raw material

・Japan Urethane Raw Materials Association

safety handling

6Fire safety on polyurethane foam

・Japan Urethane Industry InstituteMarch,2008

7

Guidance on fire safety assessment of・Japan Urethane Industry Institutepolyurethane foam March,2008

8

Q&A concerning flexible urethane foam

・Japan Urethane Foam Association2009 edition

9

Q&A on fire and fire prevention of rigid

・Japan Urethane Industry Institutepolyurethane foam May, 2009

Q36． What other points require attention in handling flexible polyurethane foams?
A: The following matters should be kept in mind:(1) Measures against static charges
Flexible polyurethane foams, which have a low electric conductivity, easily build up static charges
by friction, but such static charges will have a low probability of igniting polyurethane foams
because of very low discharge energy. Attention is required, however, during bonding operations of32

polyurethane foams using an adhesive that contains flammable solvents, because solvent vapors are
apt to ignite by static sparks and the foams may catch fire.
Measures for ignition prevention are required such as using an aqueous adhesive or an adhesive
containing fire retardant solvents, preventing penetration of the foams with liquid or vaporizedthinner, gasoline, benzine, alcohol or other low flash point solvents, keeping the foams off such
solvents, reducing the concentration of vaporized flammable solvents in the workshop, removing or
suppressing (by humidification, etc.) static charges from the environment.
(2) Goods impregnated with oils
Flexible polyurethane foams impregnated with oils may generate smoke or fire in relatively low
temperature. Pour water, and take care that such foams will not be heated. This is a phenomenon
found not only in polyurethane foams but in cotton and fabrics in general. It is reported that oils
that have permeated into these materials exposed to air are subject to autoxidation, which will leadto increased inner temperature, possibly causing emission of smoke and production of fire from theoils first and then from the impregnated materials, just like garbage getting burned by hot cooking
oil. There are instances of fire breaking out of welding or cutting sparks sticking to polyurethane
foams. Ensuring absence of foams in the neighborhood before setting to work is strongly
recommended.

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APPENDIX
Q25A Table 25-3 Major fire gases and their toxic effectFire gas

Toxic effects

Toxicity *Narcotic gas

Combining with hemoglobin in blood to form carboxy -hemoglobin, CO

LC50 ＝5000~6600

1) Carbon monoxide

reduces oxygen supply to brain tissue, resulting in loss of consciousness andppm(v/v) 1)(CO)incapacitation.

2) Hydrogen cyanide Traces of HCN can generate in fires of nitrogen containing materials. It is(HCN)

LC50 ＝110~200
ppm(v/v) 1)

carried rapidly to body (brain) and inhibits the utilization of O2 at cells.
HCN, like CO, finally depresses cerebral function, and its intoxication takes
effects rapidly.

3) Carbon dioxide

CO2 is present always in fires. It is not toxic up to 5%, but it stimulates(CO2)

breathing and increases uptake of other toxicant gases. It is a narcotic at
about 5% and subjects become intolerable within 20 min. at approximately 6%.

4) Hypoxia(low O2)

O2 concentration decreases in a compartment fire.
Low concentration below 18% is dangerous for humans. Their motor
coordination is impaired at about 14% and they may exercise faulty
judgement at about10%.2) 3)

Irritant gas

HCl generates at fires of chlorine containing materials. Irritating extremely

LC50＝1600~6000

1) Hydrogen chloride

eyes and upper respiratory tracts (as low as 100ppm), it impairs activities

ppm 2)

such as escape from fires.

RD50＝309 ppm 2)2) Acrolein

Many organic irritant materials are formed in pyrolysis and/or incomplete

LC50＝140~170

and other

combustion of organic materials. Acrolein, which irritates eyes and upper

ppm 2)

organics

respiratory tracts strongly at a few ppm, is found to be present in many fire(HCl)

RD50＝1.7 ppm 2)

atmospheres.
3) Ammonia(NH3)

NH3 irritates eyes and upper respiratory tracts.

LC50＝1400~8000
ppm 2)

It may cause pulmonary edema.

RD50 ＝303 ppm 2)4) Nitrogen oxides

NOｘ is primarily a pulmonary irritant.

NO2 : LC50＝60~ 250 ppm 2)(NOｘ)

RD50＝349 ppm 2)* LC50： Concentration statistically calculated to cause the deathof one half of the animals exposed to a toxicant for a specified time(e.g.10, 30 min.).
taken for 30 min.
* RD50： Statistically calculated concentration of a sensory irritantrequired to reduce the breathing rate of laboratory rodents by 50%.
1)ISO/TR 9122-5 (1993)
2)D.A. Purser, SFPE Handbook of Fire Protection Engineering3)G.E. Hartzell, Toxicology, 115, 7-23 (1996)

34

Section 2/ Chapter 8 (1995)

Above data arePostscript
In line with people’s growing interest in polyurethane products, there is in recent years a lot of interest in
fires involving polyurethane materials among consumers in general as well as manufacturers and suppliers.
As for rigid polyurethane foams used mainly as building materials, Japan Urethane Industry Institute(JUII) previously published Q&As concerning hazards and prevention of fire, which we believe haveprovided people with a great help to understand. Many flexible polyurethane foams are used in furniture,
mattresses and other products placed in the dwelling space, and full consideration should be paid to thesematerials in case fire should break out. We would be delighted if these Q&As published this time would
be a contribution to reducing occurrences of fire involving flexible polyurethane foams and provide anotherhelp to people to understand hazards and prevention of such fire.

Editors
Fire Safety Working Group of JUII composed of:Chairman:Kiyoshi Moriya , Nippon Polyurethane Industry Co, Ltd.

Vice-Chairman:

Toshiaki Momma , Achilles Corporation

Members (in no particular order):Hajime Nonomura, BASF INOAC Polyurethanes Ltd.
Hideya Kinoshita , Bridgestone Co.,Ltd , ( predecessor: Noriyuki Yamaguchi)
Jun Akai , Co., Ltd Soflan Wiz
Koichi Wada, Sumika Bayer Urethane Co, Ltd.
Hiroshi Inoue, Mitsui Chemicals, Inc.

Japan Urethane Industries InstituteHome page: http://www.urethane-jp.org/
Japan Urethane Foam Association
Yagumo building

Japan Urethane Raw Materials Association
Toyokaiji building

2-17-1, Nishishinbashi, Minato-ku, Tokyo

2-8-11, Nishishinbashi, Minato-ku, Tokyo

105－0003、Japan

105－0003、Japan

Phone +81- 3-6402-1252

Phone +81- 3-3591-1855© Japan Urethane Industries Institute Compiled in March, 2010.

All Rights Reserved. Except in particular cases, any reproduction, duplication, computer input ortranslation of this publication without prior permission violates the rights of the publisher and the authors.

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