Q & A on Fire and Fire Prevention of Rigid
Polyurethane Foam

1st Edition
May 2009

Translation into English by JUII Fire Safety Committee from revised
Japanese text
(December 2011)

Japan Urethane Industry Institute (JUII)Preface
Rigid polyurethane foam has been widely used as an indispensable material for andenergy conservation and improving livability in buildings on account of numerous excellent
characteristics such as processability, cost effectiveness, and insulation properties. On
the other hand, polyurethane foam fires still occur despite various countermeasures being
adopted such as flame retardation because after all the material is based on organic
polymers that have in common the characteristic of combustible properties. Therefore,
Japan Urethane Industries Institute (JUII) has carried out further activities directed at ahigher level of fire safety.
The technical safety committee of JUII has collected literature regarding polyurethane
foam fires and combustion from combustion toxicology and fire safety specialists andproceedings have been offered, while fire-prevention activities have also been promoted
in cooperation with related industries. As part of this activity, the view was that an easierexplanation of newer findings was necessary and here, a Q&A collection concerning a fireand fire prevention chiefly for rigid polyurethane foam has been compiled.
Rigid polyurethane foam insulation is usually foamed onsite onto plasterboard or withsteel sheet as the surface material in composite materials. It is a problem when the fire
relates to exposed foam.
This Q&A collects focuses on the combustibility of polyurethane foam as materials, andaims to arouse attention to risk management of flames coming into contact withpolyurethane foam directly in when new buildings are built, or existing ones are repaired
or demolished work, etc. and a fire the occurs.
It would be greatly appreciated if this document is helpful and useful for a various people
concerned with polyurethane foam to further deepen the understanding of fire and fire
prevention and contribute to as industry development.

2

Contents

I. Fire cases studies
Q1. Please introduce cases of fires involving rigid polyurethane foam.

5

Q2. What types of fires are common?

5

Q3. What types of fires have occurred abroad?

6

II. Phenomena of compartment fires
Q4. What is flashover? Does it occur in fires with polyurethane foam?

6

Q5. What is “Deflagration phenomenon”?

7

Q6. Why do flames spread faster after they reach the ceiling?

7Q7. In what situation does polyurethane foam catch fire from welding/cutting-torch
sparks?

8

Q8. To what level does the temperature rise in fires with polyurethane foam?

8

III. Combustibility and smoke evolution
Q9. What are the flash point, ignition point and oxygen index of rigid polyurethane
foam?

9

Q10. Does polyurethane foam ignite spontaneously?

10Q11. Is the combustion rate of polyurethane foam faster than those of other materials?
10
Q12. Does polyurethane foam evolve much smoke in fires like other plastic materials?
12
Q13. Is it possible to produce fire retardant polyurethane foam?

13

Q14. What is the difference between polyurethane foam and polyisocyanurate foam?
14
Q15. Is there any difference in combustion behavior between rigid polyurethane foam
and other commercial plastic foams?

315

IV. Combustion gas and its toxicity
Q16. What gases are generally evolved in building fires and what are their properties?
18
Q17. What gases are evolved in fires with rigid polyurethane foam?

18

Q18. What are the toxic effects of fire gases from rigid polyurethane foam?

21

V. Fire test methods
Q19. What are the fire test methods for rigid polyurethane foam?

23

Q20. Are there some simplified test methods for evaluating the combustibility ofpolyurethane foam?

24

Q21. Have grades such as “JIS A 1321 flame retardant class 3” or “MOC Notice 1231
flame retardant material” acquired certification?

25

Q22. What is meant by flame retardant or semi-noncombustible materials prescribedunder tests in the Building Standard Law Notification?

25

Q23. What is the difference between JIS A1321 and ISO 5660 in the fire prevention
26

material combustion test method？

VI. Fire prevention activities
Q24. What are the necessary precautions and practices to prevent fires withpolyurethane foam?

27

Q25. What activities are you performing in order to prevent fires with polyurethane
foam?

28

VII. Supplement; Dust explosion

28

Figures and tables

30

References

354

I. Fire case studies
Q1. Please introduce cases of fires involving rigid polyurethane foam.
A: In fires involving rigid urethane form, rather than occurring while the polyurethane
foam is being processed, most occur when the welding or cutting-touch work is carriedout after foam installation. When use of flames is unavoidable, thorough measures
must be implemented such as covering polyurethane foam with a nonflammabletarpaulin so that it does not come into contact with sparks or cutting away exposed
foam. Fire, however, results when these measures are neglected.
Typical examples of recent fires are introduced below.

Table 1.1. Recent cases of fires

Q2. What types of fires are common?
A: In new construction work, welding for ducts and air conditioners, etc. is carried out
after

processing of polyurethane foam, and there are numerous examples ofpolyurethane igniting due sparks from welding. In particular, if sprayed polyurethane
foam in the celling is ignited by welding work for duct construction above the ceiling,
combustion is rapid and can lead to major accidents.
5

On the other hand, in almost all case of fire in dismantling and renovation work are due
to welding and cutting-torch work being carried out without verifying the existence ofpolyurethane foam. In particular, when warehouse doors are repaired, for example,
welding work might carried out and the polyurethane foam on the back wall may be
ignited out of sight of the worker, causing a fire.

Q3. What types of fires have occurred abroad?
A: Similar cases as those seen in Japan.

A recent example was at a refrigerated

warehouse under construction in Incheon in South Korea on January 7, 2008.
Welders were welding in the machine room and sparks came into contact with oilvapors that saturated the basement floor, which had no ventilation or mobile
ventilating fan. These vapors were ignited, and the polyurethane spray foam on thewall also ignited, causing a fire that killed 40 peoples.

II. Phenomena of compartment fire
Q4. What is flashover? Does it occur in fires with polyurethane foam?
A: Flashover is a phenomenon that spreads combustion rapidly as the heat generated bya fire is accumulated in a building, inflammables such as the ceiling, sidewalls, andfurniture are heated and reach a condition where they easily combust, and the wholeroom begins to combust simultaneously at a time. (See Q8. Fig 1)
If combustibles such as indoor furniture are easily combusted, the fire spreads at theearly stage and the flashover phenomenon readily occurs.

For this reason, thecombustibility of inflammable interior materials such as walls and ceilings also greatly
influences flashover.
Flashover occurs when a fire spreads in the presence of polyurethane foam, as is thecase with general combustible materials.
The photograph below is an example of a real large scale test.

6

Photo 4.1 Flashover at room corner test ISO 9705

Q5. What is “Deflagration Phenomenon”?
A: A combustible gas is generated from imperfect combustion due to air shortage in abuilding fire.

Deflagration phenomenon is explosive combustion that occurs when air

is rapidly supplied to such a combustible gas by opening of an opening due to thetemperature rise brought about by indoor combustion.

In particular, in a firedeveloped stage in a building fire, it is easy to have flashover when air flows in fromthe openings because indoor oxygen density lowers and an incomplete combustion
state is reached.

Q6. Why do flames spread faster after they reach the ceiling?
A: When flames reach the ceiling, they spread along it in a crawling motion due tobuoyancy.

At this time, the fire spread speed quickens rapidly if there are

combustibles on the exposed side of the ceiling.

Even when the exposed ceiling is

made from nonflammable materials, the radiation heat source expands andcombustion is expanded easily as thermal radiation emitted toward the floor andcombustible furniture increases.

Thus, it is important to take refuge immediately

because it is a very hazardous situation which results when a fire grows and reaches
the ceiling.
7

Therefore, when polyurethane foam is applied to the ceiling, it is generally effective tocover it with a material that is at least semi-noncombustible or with a fire prevention
coating in order to prevent combustion spread.

Q7. In what situation does polyurethane foam catch fire from welding/cutting-torch
sparks?
A: The energy of welding sparks is significant and on this account, polyurethane foam
ignites when sparks contact with it.

Combustible gas is generated if a specific area

comes into contact with welding sparks and is heated, and it is likely that this gas willbe ignited.

Moreover, falling molten material will pierce polyurethane foam and ignite

it.
When use of flames is unavoidable, thorough measures must be implemented such as
covering polyurethane foam with a nonflammable tarpaulin so that it does not comeinto contact with sparks or cutting away exposed foam.

Q8. To what level does the temperature rise in fires with polyurethane foam?
A: The processes in a building fire are generally breakout, early stage, fire growth stage,
fully developed fire, and end stage fire as shown in Figure 8.1.

The indoor

temperature starts to rise rapidly during the growth stage, reaching a fully developed
fire stage via flashover when the entire room burns.

At this point the indoor

temperature rises most, and reaches as much as 1000°C.
There are some cases where fire relates to the polyurethane foam.

8

Figure 8.1. Temperature and concentration profiles in room fire1)

1)

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

III. Combustibility and smoke evolution
Q9. What are the flash point, ignition point and oxygen index of rigid polyurethane
foam?
A: The combustion characteristic values of combustible materials are flash point, ignition
point, and oxygen index.
The data of various materials are shown below.

Table 9.1.

Ignitability of materials

9

According to these data, neither the flash point nor the ignition point of plastics
material including rigid polyurethane foam is low compared with wood.
1)

Fire Engineering Handbook, 3rd Ed. p.800, 802 (1997)

2-a)

E.K. Moss, Journal of Cellular Plastics, Nov./Dec. 332-336 (1976)

2-b)

M.M. Hirschler, Journal of Fire Sciences, 5, 289-307 (1987)

Q10. Does polyurethane foam ignite spontaneously?
A: Polyurethane foam products do not ignite spontaneously.

Moreover, polyurethane

never ignites spontaneously under a usual foam manufacturing conditions where it ismade from mixing two components: the polyol component and the isocyanate
component.

However, the foaming process generates heat and it is possible thatspontaneous ignition may occur due to foaming excessive amounts of foam.
Therefore, making a larger block of foam than that required should be avoided, andthe application manual should be followed in order to avoid heat accumulation in thepolyurethane foam block.

Q11. Is the combustion rate of polyurethane foam faster than those of othermaterials?
A: As criteria for the combustibility of materials, the standard method for measuring the
combustion rate had been based on mass decrease when that material is combusted.
Judgment is now also possible based on the calorific value generated during
combustion. Both groups of data are compared in the table below.
Table 11.1 Materials for combustion rate test 1)

10

Table 11.2. Combustion rate test results 1)

The results show that the combustion rate of rigid polyurethane foam in terms of massdecrease and calorific value is not faster than other materials.
On the other hand, foam plastic has a large surface area, it exhibits good insulation
efficiency and it does not diffuse heats and for these reasons, it possesses the generalcharacterization that it combusts relatively easily.

Because flames might spread

rapidly if polyurethane foam ignites, sufficient measures for ignition and fire prevention
are necessary for a exposed foam.
1)

F. Saito, M. Yoshida, Annual Report, Construction Research Institute, 131-133 (1982)

2）

G.E． Hartzel, Toxicology, 115, 7-23 (1996)

11

Q12. Does polyurethane foam evolve much smoke in fires like other plastic
materials ?
A: Though smoke evolution varies according to combustion conditions such astemperature and the amount of air supplied, polyurethane foam does not necessarily
generated more smoke than other foams. The table shows data comparing smoke
evolution from various materials.

Table12. 1. Emitting smoke factor1)*1. Smoke quantity emitted per mass of sample pyrolyzed.

12

Table 12. 2.

Various smoke test results

1)

T.G. Cleary, PB 92-123033, 85-88 (1991)

2)

T. Morikawa, E. Yanai, Journal of Fire Sciences, 7, 131-141 (1989)

3)

W.D. Woolley, Journal of Cellular Polymers, 4, 99 (1985)

4)

C.J. Hilado, R.M. Murphy, Journal of Thermal Insulation 3, 276 (1980)

Q13. Is it possible to produce fire retardant polyurethane foam?
A: While rigid polyurethane foam can be made fire retardant (harder to combust) byincreasing the amount of phosphoric acid ester flame retardant or increasing theisocyanate index, it will not become fully fire retardant as long as it is an organic
material.
Flame retardance of polyurethane foam aims to increase the time available for
persons to evacuate before a fire spreads by delaying spread at the early stage of afire. The following data exists for flame retardation of polyurethane foam.

Figure 13.1. Oxygen index of flame retardant PU foams1)

1)

J.E. Kresta, Journal of Cellular Plastics 11 (2), 71 (1975)

2)

G.E. Hartzell, Journal of Cellular Plastics, 28, 330-358 (1992)
13

The oxygen index of air is 21% and combustion becomes more difficult the higher theoxygen index becomes, as shown in the oxygen indices in the above figure. However,there are limitations to flame retardation and use of isocyanurate is necessary in orderto further increase the difficulty of combustion for polyurethane foam. (see Q14)

Q14. What is the difference between polyurethane foam and polyisocyanurate
foam ?
A: Polyisocyanurate foam features improved flame and thermal resistance by using an
excessive amount of isocyanate and a special catalyst to introduce an isocyanurate
ring structure.
Though it becomes difficult to combust if a lot of these ring structures are incorporated,
it’s fault is it also easily becomes brittle and thus cannot endure practical use. Then,urethane-modified polyisocyanurate foam that makes the best use of the advantagesof polyurethane is actually used. In general, this is called polyisocyanurate
polyurethane foam.

It is clear that there is the difference in the combustibilities of polyurethane foam andpolyisocyanurate foam from test data below.

Polyisocyanurate foam does not burneasily, and the calorific value and the combustion speed are low compared withpolyurethane foam.

14

Table 14.1.

Heat release and rate of heat release1)

T.G. Cleary, J.G. Quintiere, PB Report 92-123033, p.88 (1991)

2)

A. Deleon, Journal of Thermal Insulation, 6, 169 (1983)

Q15. Is there any difference in combustion behavior between rigid polyurethane
foam and other commercial plastic foams?
A: There are two kinds of plastics foam used as construction materials.

One isthermoplastic resin such as polyethylene foam and polystyrene foam, which is meltedby heat.

Another is thermoset resin which is not melted by heat, such as

polyurethane foam, polyisocyanurate foam or phenolic resin foam.
The combustibility of a material tends to be seen in its heat release rate and grosscalorific value.

Material comparison data is shown in Table 15.1.

Because thecharacteristic of combustibility is different, these materials cannot indiscriminately be
judged to be combustible.
15

Table 15.1 Cone calorimeter: Heat release and rate of heat release 1)*1.

With external heat flux of 50kW/m2, *2. During melting, distance from regressing sample surface
to cone heater is maintained to be same as initial.

1)

T.G. Cleary, J.G. Quintiere, PB Report 92-123033, p.85-88 (1991)

IV. Combustion gas and its toxicity
Q16. What gases are generally evolved in building fires and what are theirproperties?
A: Fires and the situation regarding generation gas are classified from the standpoints ofthe gas composition and toxicity as shown in Table 16.1, although the composition
and the toxicity of the gas generated vary according to the progress of the fire.

16

Table16.1. Fire development and combustion gas evolution

HCN: Hydrogen cyanide, HCl: Hydrogen chloride, CO2: carbon dioxide,
CO: Carbon monoxide, H2O: Water, O2: Oxygen

Table16.2 shows the toxicity of the gas generated in a fire. The toxicities of theconstituent gases combine as the overall gas generated.

Table 16.2. Toxicity of major fire gases***1.

LC50： Concentration statistically calculated to cause the death of one half of the animals
exposed to a toxic substance for a specified time (e.g.10, 30 min.).

*2.

RD50： Statistically calculated concentration of a sensory irritant required to reduce the breathing
rate of laboratory rodents by 50%.

** Details in Table 16A (page-XX )Harmful gas generated in a fire and an outline of its toxicity are displayed in Table 16A.
17

On the other hand, the hazards of a fire always include heat and smoke in addition to
the gas toxicity generated from the combustion materials, and the toxicity of thegeneration gas is a part of the overall hazard of fire.
Smoke and heat negatively affect evacuation in the second stage (from early stage to
growth stage) in Table 16.1, and humans find it extremely difficult to survive in a hightemperature fire of the third stage (from fully developed stage to end stage) due to skinburns, and inhalation and heatstroke of high temperature gas, etc.

Literature references
1) ISO/TR 9122-5 (1993)
2) D.A. Purser, SFPE Handbook of Fire Protection Engineering Section 2/ Chapter 8 (1995)
3) G.E. Hartzell, Toxicology, 115, 7-23 (1996)
4) ISO/TR 9122-1(1989)

Q17. What gases are evolved in fires with rigid polyurethane foam?
A: A fire involving rigid polyurethane foam is in general the same as a normal fire.
Carbon monoxide and carbon dioxide are the main components of the gas generated,
as is the case with other organic materials. (See Q16)
Tables 17.1, 17.2 and 17.3 show the example of the combustion gas measurementfindings of various materials obtained from a small-scale experiment device.
Table 17.3 compares generation of hydrogen cyanide (HCN) from nitrogen-containing
organic materials but besides the concentration of hydrogen cyanide from flexible
polyurethane foam being relatively low, a marked difference with other materials could
not be recognized
Figure 17.1 shows an experiment example where the pyrolysis products ofnitrogen-containing material convert to HCN under high temperature, and it is foundthat the HCN conversion rate (weight ratio (%) of generated HCN to original weight ofthe material) of a material with a high nitrogen content is high18

Table 17.1.

*1

Cellulose,*2

Polyester,*3*6

Polymethylmethacrylate,*7

Combustion test products (mg/g) 1)

Polyacrylonitrile,
Polyvinylchloride,*4

olyethylene, *5.Polypropylene,*8.Methymethacrylate

Decomposition temperature；500°C, O 2 concentration: 21%, Air flow: 0.22 ml/min.
Decomposition time: 4 min. Sample weight: 100 mg

19

Table 17.2. Combustion products of organic materials 2)

Combustion parameters: temperature 700°C, air flow 100l/hr*1

Polyurethane foam made from TDI and polyester polyol

Table 17.3. Generation of HCN through combustion of N-containing materials3)20Figure 17.1.

Conversion rate to HCN for pyrolysis*1

On one hand, it is said that the gas composition of a single, small-scale experiment will
not represent the entire generation gas of a real fire because the composition of thegeneration gas is different according to the progress of a fire.
On the other hand, small-scale experiment results are used in methods for correcting
concentrations to use as input data for combustion gas models. (See Q18)
1)

T. Saito, E. Yanai, Technical Report, Fire Research Institute, No.10 5-60（1977）

2)

T. Morimoto, Highpolymers, Vol. 22, No.253, 190-195 (1973)

3)

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

4)

W.D. Woolley, et al., Fire Safety Journal, 5, 29-48 (1982)

Q18. What are the toxic effects of fire gases from rigid polyurethane foam ?
A: The combustion gas toxicity of various materials is evaluated by the LC50 value.

LC50

means that when laboratory animals are exposed to gases for 30 minutes, this is astatistical calculation value of the concentration of the combustion gas whereby 50%of the laboratory animals die. Such values lie within the range of about 5-60 mg/L for
many plastic materials and natural materials.
It can be seen from Table 18.1 that the combustion gas toxicity value of rigid
polyurethane foam is on a par with those of other plastics materials.

21

Table 18.1. Toxicity of thermal decomposition products of various plastic materials 1）*1. F; Flaming, NF; Non-flaming, M; Mixed mode
*2. Exposure time *3. Post-exposure time
* Biological data are usually distributed widely and are not judged to be significantly different
unless the differences exceed one order.

However, when the hazards of combustible gases is evaluated from the findings ofcombustion gas toxicity examinations, it is necessary to consider the difference with areal fire. (See Q17)
Table 18.2 shows a comparison between a simulation of a real fire scale andsmall-scale experiments. The data of two small-scale experiments are corrected to thelevel of a high concentration of carbon monoxide of a real fire after‐flashover.

As forthese data that simulate a real fire, it is understood that rigid polyurethane foam
exhibits no special combustion gas toxicity compared with the other two materials.

22

Table 18.2. Fire gas toxicity test of various materials 2)*1 CO values are adjusted to reflect CO evolution at real scale fire.
*2. Combustion room (2.4 x 3.7 m), Corridor (2.4 × 4.6 m), Test room (2.4 x 3.7 m)
1)

B.C. Levin, Fire & Materials, 11, 143-157 (1987).

2)

V. Babrauskas et al., Journal of Fire Sciences, 9, 125-148 (1991).

V. Fire test methods
Q19. What are the fire test methods of rigid polyurethane foam?
A: Combustibility parameters such as ignitability, flame spread, heat release, andsmoking, and harmfulness parameters such as the smoke and gases generated areelements of fire resistance performance for building materials and interior materials
that relate to rigid polyurethane foam used for building insulation.

The maincombustibility tests used in Japan are based on JIS standards, the Ministry ofConstruction notification, and ISO standards.
When speaking of combustibility testing, the test method applied is different
depending on the combustion phenomenon to be evaluated. Moreover, test methods
themselves are classified as ones to understand the basic performance of material
and ones to understand the performance of a material in a real fire. The main test
methods used to evaluate polyurethane foam are shown below.
Further, various test methods, test items, and outlines of test devices are summarized
in reference at the end of this document. ( See Q19-A,B)

23

Table 19.1. Rigid polyurethane insulation foam fire tests* *MOC; Ministry of Construction, current Ministry of Land, Infrastructure, Transport & Tourism (MLIT)** Details of main test methods, test items, and apparatus in Table 19A, (page 34-35)

Q20. Are there some simplified test methods for evaluating the combustibility ofpolyurethane foam?
A: While in some cases JIS A9511 can be used to determine the extent of low
combustibility by using a flame from a lighter or match to heat a sample, it is thoughthat comparison of flame retardant products under JIS A 1321 and suitability to eachstandard cannot necessarily be understood. This is because when comparing using
flame from a lighter, the same combustion tendency is not necessarily shown with the
JIS A 1321 test that uses a high calorie heat source (heating wire.)
Moreover,when

speakingofcombustibility,
24

there

are

severalevaluation

characteristics such as ignitability, smoking, calorific value, and combustion rate, andthe current situation is that there is no technique to adequately evaluate each of theseby a simple and easy method.

Q21. Have grades such as “JIS A 1321 flame retardant class 3” or “MOC Notice 1231
flame retardant material” acquired certification?
A: Certification is not necessarily acquired. For instance, certification is not awarded in
the case of onsite foaming.

This is because the manufacturing conditions are not

managed easily at a construction site. In a word, in the case of onsite foaming, strictly
speaking, “Grade 3 incombustibility” and “Flame resistant materials in the notificationof Ministry of Construction” are those that met relevant standards and regulations
when samples were tested by independent testing organizations, and it does not meanthat certification has been acquired.

However, in the case of onsite foaming, thecombustion performance of foams is classified by a decision of “the Building
Contractors Society” as “Grade 3 flame retardant products with pink coloring”.
Certification can be acquired from JIS standards and the Ministry of Land,
Infrastructure, Transport & Tourism (MLIT, old Ministry of Construction MOC) for
so-called factory production products such as laminate boards and insulated panels if
the flame retardant and fireproof properties of the products satisfy management items
prescribed in manufacturing.

Q22. What is meant by flame retardant or semi-noncombustible materials
prescribed under tests in the Building Standard Law Notification?
A: Generally, materials that can be used for exterior structures and interior finishingmaterials for rooms and passages are restricted by ordinances based on the usage
and structure of the building.

The objective is to suppress the danger at a fire as

much as possible by prescribing the use of materials with high fire preventions
properties for exterior and interior materials.
For example the fire preventions properties required of materials differ depending on
the usage, structure, and floor area of the building.
25

There are interior finishingrestrictions mandated as “Flame resistant material”, more than “Semi-noncombustible
material”, and “Noncombustible material” based on notification tests.

Construction iscarried out using materials certified by MLIT.

Q23. What is the difference between JIS A1321 and ISO 5660 in the fire prevention
material combustion test method?
A: The evaluation method for fire protection materials was changed along with therevision of the Building Standard Law of Japan in 1998, and the heat release test
method (ISO 5660) was adopted in place of the conventional surface combustion test
method (JIS A1321).

Then the evaluation method changed to the performance

evaluation method in June 2000.
This is because in characterizing the combustibility of materials for building
construction, heat release property is the key factor and heat release from interiormaterials is an important fire property which influences propagation and expansion ofroom fires.

Both test methods differ greatly in the heating method and evaluation

method.
The surface combustion test method is a method of evaluating heat release, smoke
generation, and residual flame.

The surface combustion test method does not

sufficiently evaluate characteristics as a fire protection material and incombustibility.
On the other hand, the heat release cone calorie meter method is a global standard
method for evaluation of the combustibility of a material. The heat generation rate
and gross calorific value are calculated by the oxygen consumption method. The test
utilizes the fact that regardless of the type of substance, an almost constant numericalvalue is obtained for the calorific value from combustion (13.1MJ per oxygen kg).
Various, engineering data related to combustion such as heat release rate, smoke
density, change with passage of time of the amount of the CO and CO2 generation,and gross calorific value, etc., are obtained upon ignition.

26

Table 23.1

Japan regulation and test methods for building construction

VI. Fire prevention activities
Q24. What are the necessary precautions and practices to prevent fire accidents
with polyurethane foam?
A: The main cause of polyurethane foam fires is welding or gas-torch work after onsite
spraying of rigid polyurethane foam. In the case of construction of new buildings, thisis because process control by site managers is insufficient and the understanding of
the combustibility of polyurethane foam on the part of welding workers is insufficient.
Moreover, in repair and demolition work, welding work is carried out without
understanding the locations of polyurethane foam in the building
The Ministry of Health Labor & Welfare (MHLW), which manages welding qualificationlectures, is urging that qualifying examinations and safety course texts for
welding-cutting torch workers should include instruction on polyurethane fire
prevention measures but it seems as though these measures have not yet beenthoroughly implemented.

On the other hand, the Building Contractors Society has

issued the booklet “Prevention of Polyurethane Foam Fires” for site supervisor andworkers at construction sites, and attention has been aroused by a hazard
27

assessment sheet that refers to past examples of incidents. Therefore, in order toprevent fires, the site supervisor should first direct safety confirmation.

Next, if thepresence of polyurethane foam is confirmed, it should be covered with anonflammable tarpaulin or removed from all sides for a distance of one meter. Then,welding-cutting torch work should be carried out in the presence of the supervisor

Q25. What activities are you performing in order to prevent fires involving
polyurethane foam?
A: The Rigid Polyurethane Safety Advisory Council was established by the Japan
Urethane Industries Institute (JUII), Japan Urethane Foam Association (JUFA) and theJapan Urethane Insulation Association in order to promote various activities regarding
safety for onsite construction by member companies. The following activities arecarried out by the council.

1. Advice to make full use of authorized safety manuals for welding.

A leaflet was

published under the supervision by Tokyo Metropolitan Fire Defense Agency
2. Safety campaigns at Japan Welding Association through trade (industry)
newspapers and journals
3. Periodical meeting with Construction Industries Association (Zenken)
4. Campaign on polyurethane fire prevention at onsite construction bodies throughthree trade newspapers.
5. Cooperation with MHLW and MLIT: advice at meeting organized by MLIT, and at
seminar for licenses by MITL.

VII Supplement Q&A Dust explosion
Q What is “Dust explosion”
A; Dust explosion is the phenomena that flammable dust floated in atmosphere withenough oxygen (dust cloud) is ignited by a source like spark and oxidized suddenly
resulted in a explosion. Because dust size is very fine, dust have a very large surface
area compared to their mass which is resulted in contact with enough oxygen, dust is28

very sensitive for oxidization and ignition.

Coal mining explosion is very famous due

to coal dust, but many otherwise mundane materials can also lead to a dust explosion
such as metal powder like aluminum, iron, and magnesium, and such as sugar andflour.

Minimum ignition energy means the minimum energy for source of ignition.

Electrostatic discharge can also become a source of ignition energy.

Q. Can polyurethane foam generate a dust explosion?
A: Because plastics are organic compounds and combustible, plastics may generate adust explosion if plastic dust is floating in atmosphere.

Polyurethane foam itself

never generate a dust explosion, but if polyurethane is powdered into fine dust, it cangenerate a dust explosion same as other plastic dust.

Because minimum ignitionenergy or explosion limit of polyurethane dust is not larger than that of other plastic
dust, the risk of dust explosion of polyurethane is not so large.
Polyurethane dust can arise from cutting, crashing and grinding polyurethane products.
Furthermore dust can arise during compounding of thermoplastic polyurethane (TPU).
In order to avoid dust explosion, following countermeasures are required; enoughventilation not to generate dust cloud, keeping ignition source away.
or high humidity is also effective as a countermeasure.

29

Nitrogen purge

Figures and tables
APPENDIX
Table 16-A. Major combustion gases and their toxic effects*1.

LC50： Concentration statistically calculated to cause the death of one half of the animals exposed to a toxic
substance for a specified time (e.g.10, 30 min.).

*2.

RD50： Statistically calculated concentration of a sensory irritant required to reduce the breathing rate of laboratoryrodents by 50%.

1)

ISO/TR 9122-5 (1993)

2)

D.A. Purser, SFPE Handbook of Fire Protection Engineering Section 2/ Chapter 8 (1995)

3)

G.E. Hartzell, Toxicology, 115, 7-23 (1996)30

Table Q19-A

Fire Test Methods

31

Table 19-B. Fire test apparatuses 1)
Surface Combustion Test

Gas Hazard Toxic test32Model Box Test

Cone Colorimeter Test

33

Fire Spread Test

Full Scale Room Test

Y. Hasemi, Seminar text on revision of Building Standard Law, July 1998
34

6. References
1)

Fire Engineering Handbook, 3rd Ed. (1997)

2)

E. K. Moss, Journal of Cellular Plastics, Nov./Dec. 332-336 (1976)

3)

M. M. Hirschler, Journal of Fire Sciences, 5, 289-307 (1987)

4)

F. Saito, M. Yoshida, Annual Report, Construction Research Institute, 131-133 (1982)

5)

G..E. Hartzell, Toxicology, 115, 7-23 (1996)

6)

T. G. Cleary,, PB 92-123033, 85-88 (1991)

7)

T. Morikawa, E. Yanai, Journal of Fire Sciences, 7, 131-141 (1989)

8)

W. D. Woolley, Journal of Cellular Polymers, 4, 99 (1985)

9)

C .J. Hilado, R.M. Murphy, Journal of Thermal Insulation 3, 276 (1980)

10) J. E. Kresta, Journal of Cellular Plastics 11 (2), 71 (1975)
11) G. E. Hartzell, Journal of Cellular Plastics, 28, 330-358 (1992)
12) A. Deleon, Journal of Thermal Insulation, 6, 169 (1983)
13) ISO/TR 9122-5 (1993)
14) D .A. Purser, SFPE Handbook of Fire Protection Engineering Section 2/ Chapter 8 (1995)
15) ISO/TR 9122-1 (1989)16) T. Saito, E. Yanai, Technical Report, Fire Research Institute, No.10 5-60（1977）
17) T. Morimoto, Highpolymers, Vol. 22, No.253, 190-195 (1973)
18) F. M. Esposito et al., Journal of Fire Sciences, 6, 195-242 (1988)
19) W. D. Woolley, et al., Fire Safety Journal, 5, 29-48 (1982)
20) B. C. Levin, Fire & Materials, 11, 143-157 (1987)21) V. Babrauskas et al., Journal of Fire Sciences, 9, 125-148 (1991)
22) Y. Hasemi, Seminar text on revision of Building Standard Law, July 1998

35

Compilation
Japan Urethane Industry Institute (JUII)
Fire Safety Committee
Kiyoshi Moriya (Nippon Polyurethane Industry Co., Ltd), Chairman
Toshiaki Monma (Achilles Co., Ltd), Vice Chairman
Hajime Nonomura (BASF INOAC Polyurethane Co., Ltd)Noriyuki Yamaguchi (Bridgestone Co., Ltd)
Hiroshi Inoue (Mitsui Chemicals, Inc.)
Koichi Wada (Sumika Bayer Urethane Co., Ltd)Jun Akai (Soflan Wiz CO., Ltd )Japan Urethane Industries Institute (JUII) was established by the Japan Urethane
Foam Association (JUFA) and Japan Urethane Raw Materials Association (JURA)
and consults on programs to maintain and improve safety and health, works onenvironmental issues, works to spread high quality products, consults on energy
conservation, and carries out public relations.
Website: www.urethane-jp.org

Japan Urethane Foam Association
2-17-1, Nishishinbashi, Minato-ku, Tokyo, 105-0003, Japan
Telephone: +81-3-6402-1252
Japan Urethane Raw Materials Association
2-23-2, Nishishinbashi, Minato-ku, Tokyo, 105-0003, Japan
Telephone: +81-3-6809-1081© Japan Urethane Industries InstituteOriginal Japanese Compiled in May. 200936