Reference NBS

PUBLICATIONS

NBSIR 85-3224

AlllDti DHmTD

A Review of the Literature on the

Gaseous Products and Toxicity

Generated From the Pyrolysis and

Combustion of Rigid Polyurethane

Foams

Maya Paabo

BartMra C Levin

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MO 20899

December 1986

QC

100

.056

85-3224

1985

'hJ in part by:

msumar Product Safety Commission

la. MD 20207

NBSIR 85-3224

#• « A REVIEW OF THE LITERATURE ON THE

GASEOUS PRODUCTS AND TOXICITY

GENERATED FROM THE PYROLYSIS AND

COMBUSTION OF RIGID POLYURETHANE

FOAMS

EESE<^CH

C£I\!TEH AfEt

D.C I'oc

, ttC_ r -

Maya Paabo

Barbara C. Levin

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MO 20899

December 1985

Sponsored in part by:

U.S. Consumer Product Safety Commission

Bethesda, MD 20207

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Dirmctor
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TABLE OF CONTENTS

Page

LIST OF TABLES iv

Abstract 1

1. INTRODUCTION 2

2. THERMAL DECOMPOSITION 5

2.1 Degradation In Inert Atmospheres 7 2.1.1 General Decomposition Studies 7 2.1.2 Volatile Products 11

2.1.3 HCN and CO Generation 13

2.2 Degradation In Oxidative Atmospheres 14

2.2.1 Volatile Combustion Products 15

2.2. 1.1 Common Toxicants 13

2. 2. 1.2 Detailed Chemical Profiles 20

2. 2. 1.3 Effects of Blowing Agents 21

2. 2. 1.4 Fire Retardants 22

2.2.2 Particulate Combustion Products 24

3. TOXICOLOGY 24

3.1 National Bureau of Standards (NBS) Toxicity Test Method 26

3.2 University of Utah Toxicity Test Method 31

3.3 University of Pittsburgh Toxicity Test Method 34

3.4 DIN Toxicity Test Method 41

3.5 Japanese Combustion Toxicity Tests 49

3.6 University of San Francisco (USF) Toxicity Test Method 53

3.7 Miscellaneous Studies 59

3.7.1 University of Michigan Tests 59

3.7.2 Mechanistic Studies of HCN and CO Toxicity 60

3.7.3 Production of Unusual Toxicity 62

4. SUMMARY 67

5. ACKNOWLEDGMENTS 70

6. REFERENCES 70

-ill-
LIST OF TABLES

Page

Table 1. Thermal degradation products produced from rigid

polyurethane foam 77

Table 2. Products for pyrolysis of a sample of a rigid urethane

foam 80

Table 3. Major combustion products from rigid polyurethane foams

decomposed in a nitrogen atmosphere 81

Table 4. Major nitrogen-containing thermal products from flexible

and rigid polyurethane foams decomposed in a nitrogen

atmosphere 82

Table 5. Temperature dependent yield of HCN from rigid polyurethane

foams decomposed in inert atmospheres 83

Table 6 . HCN generation from rigid polyurethane foams decomposed

in air at 500*’C 84

Table 7. Combustion products from rigid polyurethane foam under

flaming conditions 85

Table 8 . Release rate data for rigid boardstock polyurethane 86

Table 9. Rigid polyurethane foam (CM 30) toxicity measurements

using the NBS toxicity test method 87

Table 10. Atmospheric gas concentrations and percent carboxyhemoglobin

calculated at the LC 5 Q (30 min) values for GM 30 decomposed

by the NBS toxicity test method 88

Table 11. Toxic effects of the combustion products of rigid polyurethane

foam using the University of Utah test method 89

Table 12. Calculated CO and HCN mean concentrations generated at the

incapacitating and lethal smoke concentrations produced

during the flaming decomposition of rigid polyurethane foam

in the University of Utah studies 90

Table 13. RD50 values calculated for different rigid polyurethane foams

decomposed by the University of Pittsburgh test method 91

Table 14. Sensory irritation (RD50 ), stress index (SI 100), acute

mortality (LC 5 Q) values, and asphyxiation concentrations

from rigid polyurethane foams examined by the University of

Pittsburgh test procedure 92

Table 15. Toxicity of the pyrolysis products of rigid urethane foams

decomposed on a volume basis or a weight basis 93

-iv-
LIST OF TABLES (continued)

Page

Table 16. Toxicological effects on rats exposed to combustion products

from polyurethane foams evaluated according to the DIN

toxicity test method 94

Table 17. Toxicological effects on mice exposed to combustion

products from rigid polyurethane foam 95

Table 18. Mean time to collapse after exposure of mice to the thermal

decomposition products from a rigid polyurethane heated at

850®C 96

Table 19. Comparison of toxicity results from fire retarded vs non-fire

retarded rigid polyurethane foams decomposed according to the

University of San Francisco toxicity test method 97-

Table 20. Toxicity results for rigid polyurethane foams decomposed

according to the University of San Francisco method using

different temperature modes 98

Table 21. Effect of aging on toxicity of rigid polyurethane foams as determined according to the University of San Francisco

method 99

Table 22. Char yield and toxicity of pyrolysis gases from rigid

polyurethane foams as determined according to the University

of San Francisco toxicity test method 100

Table 23. Comparison of toxic effects from a rigid pol3narethane foam

decomposed at either fixed temperatures (300 to 800°C) or with a rising temperature program according to the University

of San Francisco toxicity test method 101

Table 24. Gas generation and time-to-incapacitation results following

exposure of rats to the combustion products from rigid

polyurethane foams decomposed according to the University

of Michigan test procedure 102

Table 25. Toxicological effects produced in rats following a 20-mlnute

exposure to CO, smoke from the combustion of Douglas fir,

rigid polyurethane foam, or a fire-retarded rigid polyurethane foam 103

Table 26. Summary of behavioral assessments of rats following 20

minute exposures to smoke from the non-flaming combustion

of fire retarded rigid polyurethane foams 104

Table 27. Acute toxicity of smoke from trimethylol propane-based

rigid polyurethane foams containing various phosphorus

additives 105

-V-
LIST OF TABLES (continued)

Page

Table 28. Toxicological effects based on 30 minute exposures to

rigid polyurethane foams thermally decomposed by different

test methods 106

Table 29. Incapacitation effects from exposure to rigid polyurethane

foams decomposed by different test methods 107

-vi-
A REVIEW OF THE LITERATURE ON THE GASEOUS PRODUCTS AND TOXICITY

GENERATED FROM THE PYROLYSIS AND COMBUSTION OF RIGID POLYURETHANE FOAMS

Maya Paabo and Barbara C. Levin

Abstract

The literature on rigid polyurethane foam has been reviewed with an

emphasis on the gaseous products generated under various thermal decomposition

conditions and the toxicity of those products. This review is limited to

publications in English through 1984. Carbon monoxide (CO) and hydrogen

cyanide (HCN) were the predominant toxicants found among more than 100 other

gaseous products. The generation of CO and HCN was found to increase with

increasing combustion temperatures. Many test methods were used to assess the

acute inhalation toxicity of combustion products from various rigid polyurethane foams. Lethality, incapacitation, physiological, and biochemical

parameters were employed as biological end points. In general, the combustion

products generated from rigid polyurethane foam in the flaming mode appear to

be more toxic than those produced in the non-flaming mode. The LC^q values

for 30 minute exposures ranged from 10 to 17 mg/1 in the flaming mode and were

greater than 34 mg/1 in the non-flaming mode. With the exception of one case

in which a reactive type phosphorus containing fire retardant was used, the

addition of fire retardants to rigid polyurethane foams does not appear to

generate unusual toxic combustion products.

Key words; carbon monoxide, combustion products, fire retardants,

hydrogen cyanide, literature reviews, polyurethane foams, rigid foams, thermal

decomposition, toxicity.

- 1 -
1 . INTRODUCTION

Rigid poljmrethane foams have been in commercial production for about

thirty years. In 1983, about 255,000 metric tons of rigid polyurethane were

produced. Of this, the largest portion, 140,000 metric tons, was used for

building insulation; the second greatest use, about 50,000 metric tons, was

for thermal Insulation in domestic and commercial refrigeration [1]^. Rigid

polyurethane also is used for structural portions of furniture and decorative

paneling.

This report reviews the literature on rigid polyurethane foams with

special emphasis on the gaseous products generated under various thermal

decomposition conditions and the toxicity of those products. Only those

papers which were published in English through 1984 and which specifically

identified the foam studied as rigid polyurethane were used for this review.

The generic term polyurethane has been employed in the scientific and

commercial literature to refer to those polymeric materials in which the

repeated structural units are urethane linkages (see equation 1). The

complete formulations, however, of these polyurethanes (both rigid and

flexible) are proprietary and therefore unknown. When these materials are

thermally decomposed under various conditions, specific gaseous products may

be measured and the toxicity of the resultant atmospheres can be assessed.

However, since the exact formulations of the foams are unknown, conclusions as

to the toxicity of the gaseous thermal degradation products from a particular,

different polyurethane can only be estimated.

^ Numbers in brackets refer to the literature references listed at the end of

this review.

-2-
Rigid polyurethane foams are prepared primarily by the reaction of

polyisocyanates with polyol compounds as follows:

H O

nR-N=C=0 + nHO-R'-OH —£r-N-C-0R'0}„ (1)

isocyanate polyol polyurethane

Further reaction of the urethane groups with Isocyanates may take place to

form allophanates. Common Isocyanates shown below Include 4, 4 ’-diphenylmethane dllsocyanate (MDI), Its polymeric form - polymethylene polypheny11 socyanate (as typified by PAFI ), and to a lesser extent mixtures of 2,4 and 2,6

Isomers of toluene dllsocyanate (TDl).

o=c=n-o-ch2-0“N=c=o

N = C = 0

I

CH3

’ -N=C=0

CH3

0=C = N-|i^-N = C = 0

N=C=0

2,4 Isomer 2,6 Isomer

MDI

PAPI

TDl

Certain commercial materials are identified in this review in order to

adequately specify the experimental procedure. In no case does such

Identification liq>ly recommendation or endorsement by the National Bureau of

Standards, nor does it Imply that the material Identified Is necessarily the

best available for the purpose.

-3 -
The primary bloving agents for rigid polyurethane foams are (Inert) chloro"

fluorocarbons. In addition, the Isocyanates will also react In the presence

of vater to form carbon dioxide (CO2

) and amines (equation 2). The CO2

performs as a bloving agent and the amines may react further vlth the

Isocyanates to form dlsubstltuted ureas (equation 3).

H O

R-N = C = 0 + H 2 O —[R-N-C-OH]—^R“NH2 + CO 2 (2)

isocyanate water amine carbon

dioxide

H O H

I II I R-NH 2 + R-N = C = 0 —^ R-N-C-N-R (3)

amine isocyanate disubstituted

urea

In the presence of excess Isocyanate, the above products undergo

additional reactions yielding allophanate and biuret structures (see belov)

that may produce further crosslinking.

o

II -N-C-OI C-NII I O H

allophanate

O H

II I -N-C-NI C-NII I O H

biuret

The source of the hydroxyl groups are polyols containing ether or ester

linkages. The most common polyols are based on propoxylated sucrose, aromatic

polyamines, pentaerythrltol, and sorbitol. The numerous formulations of rigid

polyurethane foam may also Include surfactants, fire retardants, fillers, and

catalysts, such as tertiary amines or organo-tln compounds [la].

-4—
2. THERMAL DECOMPOSITION

The combustion of rigid polyurethane foams can produce numerous gaseous

products. Many of the analytical studies to Identify these volatile products

have been performed under various controlled atmospheres ranging from

completely inert to oxidative. Although real fires normally occur under

oxidative environments, examination of the thermal decomposition products

generated under controlled atmospheres provides information about the

molecular mechanisms of degradation. This information is also important in

understanding the thermal effects on materials which are decomposed in real

fires under vitiated conditions. Table 1 presents a compilation of all the

combustion products identified in the scientific papers reviewed for this

report. The composition of the combustion products depends largely upon the

formulation of the foam as well as the conditions of thermal degradation,

l.e., temperature, oxygen availability, and ventilation. It should be noted

that many of these products are the same regardless of whether the atmosphere

was inert or oxidative. Complete combustion yields carbon dioxide (CO 2

) and

water (H2O). However, during incomplete combustion in either a flaming or

non-flaming mode, many other compounds, such as carbon monoxide (CO), oxides

of nitrogen (NO^), hydrogen cyanide (HCN), hydrocarbons, oxygenated organic

compounds, and nitrogen-containing organic compounds, are produced.

Thermal decomposition of polyurethanes can be represented by the

following general types of reactions:

-5-
A Dissociation to Isocyanate and alcohol

H O

R-N-C-O-R' —R-N=C = 0 + R'-OH (4)

urethane isocyanate alcohol

B. Formation of a primary amine and an olefin

H O

R-N-C-O-CH 2“CH 2-R'

urethane

HO H

[R-N-C-OH] + H2C=C-R'

1 olefin

R-NH2 + CO2

primary amine

C. Formation of a secondary amine

(5)

HO H

R-N-C-O-R' —R-N-R' + CO 2

urethane secondary

amine

( 6)

Much of the early work to identify these Initial degradation steps has

been reviewed by Saunders et al. [2,3]. Many of these papers Involved differential thermal analysis (DTA) and thermogravlmetrlc analysis (TGA) along with

the Identification of functional groups to Indicate those reactions that may

have occurred. One of these studies Includes the work by Backus et al. [A],

the results of which agree, in general, with degradation reactions 4, 5, and 6

sho%rn above. Backus et al. , using TGA, degraded several formulations of rigid

polyurethane foam in helium and air and identified the functional groups in

the residual chars and the volatile gases by infrared spectroscopy. The

—6—
volatile products detected included CO2

, CO, alkenes, mixtures of organic

compounds characterized by —NH, -OH, —COC—, and monosubs tituted phenyl groups.

Although further work has been published on several mechanistic aspects, the

detailed degradation reactions have not yet been fully elucidated [5,6,7].

The following sections of this review cover the more recent experimental

studies and are separated according to the atmospheric conditions under which

the experiments were performed.

2.1 Degradation in Inert Atmospheres

2.1.1 General Decomposition Studies

When rigid polyurethane foam is exposed to elevated temperatures under

real fire conditions, even more extensive degradation occurs than indicated by

the reactions in equations 4 to 6 . In an attempt to determine the detailed

mechanism of degradation and to identify the further breakdown products which

may be of toxicological concern, several studies have been performed in helium

or nitrogen atmospheres under pyrolytic conditions at controlled temperatures.

Bott et al. [ 8 ] found that small quantities of CO, HCN, and ammonia (NH3

) were

generated when a sample of a highly crosslinked polyurethane (formulated from

diphenyl diisocyanate and polyethylene oxide alcohol) was decomposed under

either nitrogen or air atmospheres in a tube furnace over a temperature range

of 300 to 750‘*C. The volatile gases were analyzed by Draeger tubes , infrared

(IR), and mass spectrometric (MS) techniques. The generation of CO, HCN, and

—

It should be noted that the use of colorimetric tubes, such as Draeger

tubes, provides unreliable and, at best, semiquantitative results, primarily

because other combustion gases may interfere in the analysis. The

temperature of the gas being sampled also has been noted to have an effect

on the results [9].

-7 -
NH^ was shown to be temperature dependent. In nitrogen atmospheres, rapid

evolution of CO was detected at the lowest temperature (400 “C), followed by

HCN at 550 "C and NH3 at 600 ®C. At 500 ®C, the relative concentrations of GO,

NH^, and HCN were 500, 250, and 20 ppm, respectively. When the foam was

heated at high enough temperatures (>500“C) to ensure complete decomposition,

the yield of HCN was 14 mg/g of foam. Since HCN was detected before NH2

, Bott

et al. postulated that HCN Is not produced as a secondary reaction from NH^

and carbon, but Is produced from the relatively stable carbon-nitrogen groups

In the foam.

Napier and Wong [10] evaluated the generation of phosphorus-containing

compounds from fire retarded polyurethanes thermally decomposed in atmospheres

of different oxygen concentrations or in nitrogen. Two rigid polyester polyurethane foams treated with FYROL 6^ or trichloroethyl phosphate^ were

decomposed in a glass reaction vessel over a temperature range of 220 to

400“C. The degradation products were analyzed by elemental analysis, wet

chemical techniques, and infrared spectroscopy. In experiments with both fire

retarded foams, CO2 and alkenes were produced and the infrared spectra indicated the presence of functional groups corresponding to C-F and C-Cl in the

gaseous products and to -OH, C-0-, “NH2

, -NCO, and urea in the liquid

products. The type of fire retardant appeared to influence the degradation

The chemical name for FYROL 6 is 0 ,0-diethyl-N,N-bis(2-hydroxyethyl)-

aminomethyl phosphonate. FYROL 6 is a reactive fire retardant, l.e., it is

chemically incorporated into the foam by reacting like a polyol and

replacing a portion of the polyether in the formulation.

^ Trichloroethyl phosphate is the fire retardant name that was used in the

paper being reviewed. It is highly probable that the authors were referring

to tris( 2-chloroethyl) phosphate, a commonly used fire retardant.

Tris(2-chloroethyl) phosphate is an additive fire retardant, i.e., it is

physically added to the foam during formulation.

-8-
mechanism. For example, the foam containing FYROL 6 produced compounds which

corresponded to equations 4 and 5; whereas, in the case of the foam containing

trichloroethyl phosphate^, depolymerization according to equation 4 seemed to

constitute the main reaction. Phosphorus-containing compounds were observed

when the foam treated with trichloroethyl phosphate^ was decomposed at each

tested temperature or when the foam with FYROL 6 was thermally degraded at

temperatures greater than 320“C. In addition to the phosphorus compounds,

chlorine was also generated from the foam containing trichloroethyl

phosphate^.

Woolley et al. [5,11,12,13] have conducted a major Investigation of the

general mechanism of thermal degradation of polyurethane foams and identified

the nitrogen-containing combustion products. They suggested that flexible and

rigid polyurethane foams decompose by different mechanisms. Using elemental

ultramlcroanalysis, Woolley et al. monitored the nitrogen content of the

residues of several flexible and rigid foam samples decomposed under inert

(nitrogen) pyrolytic conditions in a tube furnace. The flexible foams

exhibited a rapid loss of most of their nitrogen at low temperatures (about

300"C) while losing only aproximately one third of their mass; whereas with

the rigid foams, the higher the temperature (200 to 500®C), the greater the

nitrogen and weight loss. This suggests that in rigid foams the nature of the

fragmentation process is temperature dependent [11].

Other studies showed that at relatively low temperatures (300“C) the

flexible foams decompose by the depolymerization reaction (equation 4) into a

"yellow smoke" (mainly polymeric isocyanates) and a residue (mainly polyol).

When subsequently heated at elevated temperatures (over SOO^C), the "yellow

-9-
smoke” condensates form HCN and various other nitrogen-containing compounds.

When the yellow smoke or the foam was heated at 1000 “C, about 70% of the

nitrogen in the original foam was converted to HCN [12].

In contrast, rigid polyurethane foams release some polyol at low temperatures (ZOO-SOO^C) and then, as the temperature increases, undergo uniform

fragmentation and produce both isocyanate and polyol in about equal proportions [5,13]. In these studies, four MDI/polyester and polyether type rigid

foams (two of which contained phosphorous fire retardants) as well as samples

of the component compounds , polyols and isocyanate , were thermally decomposed

at degradation temperatures up to 1000"C. Volatile decomposition products

were collected in traps and analyzed by gas chromatographic (GC) and gas

chromotographic/mass spectrometric (GC/MS) techniques. These studies also

showed that most of the volatile phosphorus compounds were generated below

200 ®C and the majority of the gaseous products from the polyol were produced

between 300 and 600 ®C. In addition, they found that the particulates in the

smoke were primarily fragmented polyurethanes [13].

Chambers et al. [7] also studied the mechanism of both flexible and rigid

polyurethane decomposition. By using an array of model compounds and

analyzing the residues and volatiles by various analytical techniques [IR,

nuclear magnetic resonance (NMR), GC, and MS], they showed that, at 300“C, the

degradation mechanism involves o-acyl fission of the urethane linkage with the

formation of volatile polyureas (TDI-type flexible foam) or non-volatile

polycarbodiimides (MDI-type rigid foam). Above 600 ®C, both the polyureas and

polycarbodlimides decompose further to yield nitriles and olefinic and

1

3

aromatic compounds. With a C labelling technique, HCN and nitriles were

shown to originate from the breakdown of the aromatic ring of MDI.

- 10-
Another major investigation to establish the decomposition mechanism as

well as to Identify toxic products formed during thermal degradation of rigid

polyurethane in an inert atmosphere was conducted by Voorhees et al. [6].

They studied the thermal decomposition of a laboratory formulated rigid foam

based on polymethylene polyphenyl isocyanate (PAPI) and propoxylated

trimethylol propane (TMP). The pyrolysis of the samples was performed with a

commercial pyrolysis probe or in a glass reaction tube at 500, 750, and

1000“C. The volatile products were identified by GC/MS, gas chromatography

with chemical ionization mass spectrometry (GC/CIMS), and IR analytical techniques. The finding of thermal degradation products, such as low molecular

weight alkenes, aldehydes, methanol, and aniline, supports the dissociation

steps depicted in equations 4 and 5. In contrast, the secondary amines

suggested in equation 6 were not detected in either the volatile products or

in the non-volatile particulate matter. The results of Voorhees et al.

suggest that the two pathways (equations 4 and 5) proceed through common

Intermediates involving allyl ether and methyl substituted vinyl ether. In

addition, they found that the polyol fraction decomposes by a systematic

sequence rather than a random breakdown [6,14].

2.1.2 Volatile Products

The number and type of volatile compounds detected as decomposition

products of rigid polyurethane foam in inert atmospheres depend on the degradation conditions and the analytical techniques employed. Voorhees decomposed

a rigid polyurethane foam at 500, 750, and 1000®C and identified 51 compounds

by GC/MS including saturated and unsaturated hydrocarbons, oxygenated

compounds, aromatics, nitrogen-containing compounds, CO, CO

2

, and water. Of

-11 -
these, 18 GC peaks were ascribed to propoxylated trlmethylol propanes . In

addition to the 51 compounds mentioned above, seven peaks were not identified.

The major volatile decomposition products that were identified and their

concentrations are listed in Table 2. Decomposition at 1000®C produced three

times more volatiles than at 500“C [6,14]. However, no HCN was detected under

these experimental conditions.

Mumford et al. [15] pjnrolyzed samples of an unknown rigid polyurethane

foam with a commercial pyrolysis probe and analyzed the volatile products by

GC/MS. In addition to detecting 20 compounds similar to those listed in

Table 2, they also identified aromatic amines, an indication that the unknown

foam was probably an MDI-based polyurethane.

With GC/MS and IR techniques, Woolley and his co-workers identified low

molecular weight hydrocarbons, aromatic compounds, HCN, and aliphatic and

aromatic nitriles as the combustion products of several rigid polyurethane

foams that were thermally decomposed above 700®C [13]. The results of a

quantitative analysis of eight major combustion products obtained from four

different types of rigid foams, two of which were flame retarded, are shown in

Table 3.

Even though the degradation mechanisms at low temperatures are different

for rigid and flexible foams [5,11,12,13,16], both types of foams yield

similar products at elevated temperatures. For example, all of the major

products listed in Table 3, except naphthalene, were also found among the

degradation products of TDI formulated polyester and polyether type flexible

foams which were decomposed at 800“C [12]. Similarity of the high temperature

- 12 -
degradation products between rigid and flexible foams was also observed by

Chambers and Reese [16]. Specially formulated foams based on 2,4- and 2,6-TDI

were degraded over a temperature range of 800 to 1000®C (these temperatures

are higher than those typically found in fires). The volatiles from the

decomposition of the smoke were analyzed by GC. The yields of the major

nitrogen-containing products, namely HCN, acrylonitrile, acetonitrile, benzonltrile, and pyridine from the rigid foams were very close to those found when

the flexible foams were decomposed under similar conditions (Table 4) [16].

2.1.3 HCN and CO Generation

HCN appears to be the predominant nitrogen-containing compound produced

when rigid polyurethane foam is decomposed at high temperatures [13,16]. At

1000®C, the yield of HCN from four rigid foams varied between 38 and 73 mg/g

which indicated that 27.8 to 42,8% of the nitrogen was recovered as HCN [13].

The Increase in evolution of HCN with increasing temperature was also observed

by Michal when he degraded nitrogen-containing polymers in a tube furnace

[17]. An ultraviolet spectrophotometric method was used for measuring the HCN

in the volatile products of a commercial polyurethane insulation foam. HCN

increased from 0.5 to 60.7 mg/g as the temperature increased from 600 to

1200 ®C. These results and those of several other studies which indicate the

temperature dependence of HCN generation are summarized in Table 5.

CO is produced under inert conditions from polyurethane foam since it

contains oxygen in its molecular structure. Voorhees et al. [6] in a study on

a flame retarded rigid foam showed that the production of CO increases with

increasing temperature. The evolution of CO from the rigid polyurethane foam

-13-
increased from 0.29 mg/g at 500®C to 2.8 mg/g at 750®C to 26.5 mg/g at 1000“C.

Therefore, the generation of both CO and HCN from rigid pol3mrethane increases

with increasing temperature.

2.2 Degradation in Oxidative Atmospheres

In order to evaluate the toxic atmosphere produced by rigid polyurethane

foams under flaming or smoldering conditions similar to those found in real

fire situations, the evolution of combustion products has been studied under

oxidative conditions. Most of the studies have been performed in small-scale

laboratory experiments, although large-scale burns would probably simulate

real fire atmospheres more accurately.

Small-scale tests performed under non-flaming oxidative pyrolysis are

representative of the early stages of a fire in which oxygen levels are relatively high (>16%) and the heat flux is relatively low. Under such conditions, volatile product profiles are very complex and may contain many different types of chemical species, such as hydrocarbons, aldehydes, ketones, and

nitrogen-containing compounds. Flaming tests represent fires close to or

following flashover during which the oxygen levels would drop rapidly and the

heat flux would be high. In these tests, the profile of combustion products

is relatively less complex consisting of more thermally stable compounds, such

as aromatics. In both the flaming and non-flaming oxidative cases, CO and CO

2 are the predominant products produced, but HCN has also been found in toxicologically significant quantities under these conditions.

-14-
Many of the papers surveyed in this section did not distinguish between

oxidative pyrolysis and flaming combustion. In many cases, the sample size

was limited and the emphasis was on the temperature of decomposition rather

than on the occurrence of flaming. Whenever possible, this distinction will

be made in this review.

2.2.1 Volatile Combustion Products

2. 2. 1.1 Common Toxicants

Although the production of volatile combustion products from rigid polyurethane foam in air has been studied over a wide range of temperature and

ventilation conditions, few detailed analyses of the products have been done.

In most cases, interest has centered on the common toxicants, such as HCN and

CO. However, in many flaming experiments, NO^ generation has also been

measured.

Michal [18] evaluated the generation of CO from a number of polymeric

materials, including rigid polyurethane foam, under different oxygen (O2

)

concentrations in order to simulate real-fire conditions in which the O

2

concentration in the atmosphere can vary widely. Using GC, he determined the

amount of CO generated from rigid polyurethane foam decomposed in the flaming

mode under limited O

2 conditions in a combustion chamber (CAB 4.2) set at

temperatures between 500 and 800 **C. The CO concentration varied from 121 to

154 mg/g with an average of 141 mg/g. The CO content in the combustion

products of the polymeric materials studied, including rigid polyurethane, was

shown to increase with increasing temperature.

-15-
Evolution of CO, HCN, and NH2 from a highly crosslinked isocyanate-based

rigid polyurethane foam decomposed in nitrogen and in air was studied by Bott

et al. [ 8 ]. At 500“C, the relative concentrations of CO, HCN, and NH3 generated from one gram samples in air were 5000, 200, and 500 ppm, respectively.

When samples of the foam were completely degraded at temperatures greater than

500 “C, 13.5 mg/g of the foam was recovered as HCN. Comparison of the results

obtained in air and in nitrogen (see Section 2.1.1) shows that CO, HCN, and

NH

3 evolve at lower temperatures in air than in nitrogen. That is, CO, HCN,

and NH3 start to evolve rapidly in air at 300, 400, and 450 "C and in nitrogen

at 400, 550, and 600“C, respectively. CO, however, evolves at a slightly

lower temperature than HCN in both atmospheres. As the calculated apparent

activation energies for HCN and CO production were not found to be greatly

different in air and in nitrogen (95 vs 73 kJ/mole for HCN and 76 vs

74 kJ/mole for CO), Bott et al. concluded that the presence of oxygen does not

affect the mechanism of HCN and CO generation.

The generation of HCN from polyurethane foams also appears to be

dependent on the specific chemical formulation [19]. Specially prepared

polyurethane (rigid and flexible) and isocyanurate foams based on TDI and PAPI

formulations (some with phosphorus-containing fire retardants) were pyrolyzed

in both air and nitrogen atmospheres in a tube furnace at 500“C, the temperature at which maximum evolution of HCN was found to occur in air. The evolved

HCN was measured by a colorimetric technique using a spectrophotometer.

Amounts of HCN generated from ten different rigid foams decomposed in air are

listed in Table 6.

-16-
With the PAPI-based foams, the quantity of HCN evolved during decomposition in air appeared to be related to the nitrogen content of the foam. This

was not found in the TDI-based foams, which produced much less HCN than the

PAPI type foams except in the case of the foam prepared with crude,

undistilled TDI. The presence of a phosphorus-containing fire retardant

(FYROL 6) was found to reduce the HCN evolution [19].

After comparison of HCN generation data from rigid polyurethane foam

decomposed in air and in nitrogen, Ashida concluded that oxygen may be necessary for the generation of HCN [19]. The effect of oxygen on the amount of

HCN generated was demonstrated with a modified isocyanurate foam which

produced about thirty times more HCN in air than in nitrogen and with one of

the PAPI based foams which produced 11.5 mg/g HCN when decomposed in air and

only 0.23 mg/g HCN when decomposed in nitrogen. TDI-based foams, however, did

not follow this pattern, i.e., about the same amount of HCN (0.5 mg/g) was

generated in air and in nitrogen [19].

The dependence of HCN generation on the chemical formulation of the foam

is also suggested by the results of Gaskill [20], who evaluated smoke development from four rigid polyurethanes decomposed under flaming (2.5 W/cm ), nonventilated conditions in the NBS Smoke Chamber. Colorimetric tubes^ were used

to determine the approximate quantities of HCN and CO produced (Table 7 ) . The

highest levels of HCN, 100 ppm, were generated from the non-fire retarded

PAPI-ester based foam and the fire retarded MDI-sucrose based foam. Similar

to the results of Ashida, Gaskill observed that two other fire retarded PAPI

foams produced considerably less HCN (10 and 32 ppm) than the non-fire

retarded PAPI foam. The production of CO followed the general pattern of HCN

- 17-
evolution. In one case, involving the fire retarded PAPI-ether/fluorocarbon

foam, HCl was detected, an indication that the blowing agent and possibly the

fire retardant was halogenated [20].

Evolution of HCN does not only depend on the atmosphere and the chemical

formulation but also on the temperature of decomposition. Michal [17]

conducted a systematic study of HCN concentrations generated from commercial

polymeric materials (including a rigid polyurethane insulation foam) which

were pyrolyzed under oxidative conditions at controlled temperatures ranging

from 600 to 1200®C. The results in nitrogen atmospheres were described in

Section 2.1.3. In air, the yields of HCN were as follows: 15.8 mg/g at

600‘*C, 7.4 mg/g at 800*C, 33.9 mg/g at lOOO^C, and 48.1 mg/g at 1200“C. With

the exception of 800 “C, it appears that increasing temperatures produce

increasing amounts of HCN. However, when compared to the results in nitrogen

atmospheres, more HCN is generated in air at 600 ®C, about the same amount is

produced at 800 “C, and less is found at the higher temperatures. These

results at 600 “C showing an increased evolution of HCN in air than in nitrogen

agree with results of Ashida et al. at 500“C [19].

Michal 's results [17] indicate that the HCN evolution in air increases as

the temperature Increases from 800 to 1200"C, whereas Ashida found that the

HCN evolution in air peaked at 500®C. However, since the highest decomposition temperature examined by Ashida et al. was 700 ®C, they would not have

observed the increase in HCN evolution shown by Michal at the higher

temperatures.

- 18-
NO^, In addition to HCN, CO, and CO2 , has been detected in experiments

Involving the flaming combustion of rigid polyurethane foam. The change from

pyrolysis to flaming combustion may convert the nitrogen-containing decomposition products to nitrogen oxides. This reaction, which occurs especially

under high O

2 conditions, has been demonstrated in combustion studies on HCN,

acetonitrile, and acrylonitrile using a hydrogen diffusion flame [23]. To

evaluate the thermal performance of rigid polyurethane foam, Herrington [24]

used the Ohio State University heat release rate apparatus, (this instrument

was not designed to simulate a real fire but rather to generate data for

illustration and comparison purposes only). The generation rates of NO^, HCN,

CO, and total hydrocarbons and the times to the maximum generation rate were

measured when a rigid polyurethane boardstock was exposed to a heat flux of

1 W/cm and a 0.18 kW ignition source (Table 8). During these experiments,

this foam ignited about 9 seconds after exposure. This was approximately the

time of the maximum generation rate of the volatile organic compounds. The

maximum rate of generation of the CO and CO2 came later during the flaming

combustion. The maximum generation rate for NO^ was about three times more

than that for HCN, both of which occurred during flaming mode about 12 to 13

seconds into the test.

Ball et al. [25,26] compared the production of the toxicants, NO^, CO,

and HCN, in both room and building tests in which an isocyanate based rigid

foam was thermally decomposed. The room tests were conducted by burning

paper—covered foam slabs in a 25 m^ room. Volatile gases were measured with

Draeger tubes . The average gas concentrations found in the room after 20

minutes were 225 ppm for CO, 20 ppm for HCN, and 5 ppm for NO^. These concentrations were similar to those measured during large-scale tests conducted in

-19-
buildings constructed with panels in which rigid polyurethane foam was sandwiched between steel facings. In these tests, the average concentrations were

100 ppm for CO, 7 ppm for HCN, and 8 ppm for NO^. Ball et al. compared these

results to concentrations designated by Sax [27] as dangerous to man in 30 to

60 minutes (00:1000-1200 ppm, HCN:100-200 ppm, N0^:100-150 ppm) and concluded,

in spite of the fact that none of these gases reached dangerous levels, that

CO is probably the only toxic combustion product of concern from rigid polyurethane foam.

2. 2. 1.2 Detailed Chemical Profiles

The thermal degradation of rigid polyurethane generates a great variety

of compounds, in addition to the commonly recognized toxicants HCN, CO, and

NO^. Because of the known complexity of these other combustion products, the

analytical techniques and sampling procedures are more sophisticated than the

required routine instrumentation used to collect the information on the more

common toxic combustion products.

A flame-retarded rigid polyurethane foam was burned under flaming conditlons in a 23 m room and the combustion products were analyzed by MS and IR

[26]. The following organic compounds were detected: aniline, toluidine,

dichlorobenzene, trichlorofluoromethane, carbon tetrachloride, ethanol,

acetamide, and ammonia. The presence of toluene, benzene, methane, and

acetone was also suggested by these analytical techniques. The concentration

of the primary amines in the combustion atmosphere was estimated to be 4 ppm;

the amounts of the other gases were not quantified.

-20-
During their studies of hazards generated in underground mines, Paciorek

et al. [28] and Hartstein and Forshey [29] analyzed the toxic products

produced when synthetic materials overheat or bum. In their first series of

experiments, commercial samples of rigid polyurethane were decomposed in a

"stagnation” burner arrangement through which preheated air was passed. These

conditions were designed to simulate oxidative pyrolysis and combustion. Gas

samples were collected and analyzed by GC, MS, and IR. Because of condensation in the ampoules during sampling, only a few volatiles, such as C02> CO,

HCl, trichlorofluoromethane, ethylene, propylene, propane, and acetylene were

detected [28,29].

In a second series of experiments, Hartstein and Forshey decomposed two

MDI type rigid polyurethane samples under static conditions in a glass

reaction vessel at 365 to 370“C [30]. The sampling technique was improved to

include analyses of condensible compounds. In addition to GC, MS, and IR

techniques, wet chemical procedures were used for measuring Cl”, CN” and

With these sampling techniques, no CO and only traces of HCN were

detected. The major fractions of the detected volatiles were oxygenated and

halogenated compounds. The main toxic component was aniline. Also found were

the toxic compounds chloroethanol and chloroisopropanol. The other products

identified in these experiments are listed in Table 1 in conjunction with

reference 30.

2. 2. 1.3 Effects of Blowing Agents

Evidence of the blowing agent used in the formulation of the foam is

usually observed in the degradation products [6,14,15,26,28,29,30]. In some

-21 -
studies, the blowing agent, such as trlchlorofluoromethane (FREON 11), was

detected unchanged. In other cases, thermal degradation products of the

blowing agent Itself, such as -CF and HCl have also been detected [10,20,30].

In the course of evaluating the fire performance of structural foam

materials, Lee et al. decomposed a specially fabricated rigid polyurethane

foam In which 1 ,2-dlbromote trafluoroe thane (HALON 2402) was used as the

blowing agent [31]. In the NBS smoke chamber, the rigid polyurethane foam was

subjected to a heat flux of 2.5 W/cm with and without a pilot flame for

3 flaming and non-flaming degradation, respectively. Colorimetric tubes were

used for measuring the primary toxic combustion products - CO, HCN, NO^^, HBr,

and HF. The average concentration of all the products was higher In the

flaming mode than In the non-flaming mode. For example. In one case, the

average concentrations of HBr and HF were 40 ppm and 30 ppm In the flaming

mode and 22 ppm and 3 ppm In the non-flaming mode. As HBr and HF are

compounds of toxicological concern, the contribution of the blowing agent to

the toxicity of the fire atmosphere generated by the thermal degradation of

rigid polyurethane foam must be considered.

2.2. 1.4 Fire Retardants

The addition of fire retardants to the polyurethane formulations will

also Influence the composition of the thermal degradation products. An

untreated foam produced more HCN than a PAPI foam treated with either a

reactive fire retardant (FYROL 6^) or an additive fire retardant [trls-(2-

chloroethyl)phosphate ] when thermally decomposed [19]. Phosphorus compounds

were detected In the combustion products of fire retarded rigid polyurethane

-22-
foams decomposed in air or In nitrogen [10]. The additive type fire

retardant, trichloroethyl phosphate^, evolved unchanged from the foam when

heated at low temperatures (160 to 180°C) [10].

The research which is probably most responsible for the Inception of the

field of fire toxicology as known today concerned the acute inhalation

toxicity of the nonflaming combustion products from a laboratory-formulated

PAPI/propoxylated trimethylolpropane rigid foam containing the reactive fire

retardant 0,0-diethyl-N,N-bis-(2-hydroxyethyl)aminomethyl phosphonate [32].

Convulsions were observed in rats exposed to these combustion products. After

extensive analytical studies using GC, NMR, and CIMS techniques, a highly

toxic bicycllc phosphate ester was detected and identified as 4-ethyl-lphospha-2,6,7-trioxabicyclo[2.2.2] octane-l-oxide. It was postulated that

this bicycllc phosphate ester was formed by the reaction of the fire retardant

and trimethylolpropane, one of the thermal degradation products [33]. The

formation of this bicycllc phosphate ester was also observed by Woolley and

Fardell in the combustion products from flexible and rigid polyurethane foams

and from isocyanurates commercially produced in England until 1974/75 [34].

They found that decomposition of the foams in a tube furnace at 500“C produced

up to 0.03 mg of the highly toxic bicycllc phosphate ester per gram of foam.

Foams of this composition are no longer manufactured in England. (For

additional details on the toxicity of this fire retarded foam, see section

3.7.3.)

-23 -
2.2o2 Particulate Combustion Products

Some of the complex organic compounds generated during flaming or nonflaming combustion do not remain as gaseous products In the fire atmosphere

but condense onto smoke particulates. Because of their potential toxic

nature, the Identity of these compounds Is also Important. However, only one

study has been performed on smoke particulates from a rigid polyurethane foam

[35]. Joseph and Browner thermally decomposed a foam under smoldering conditions and Identified many compounds In the particulate fraction of the smoke.

They used a complex scheme of chemical extractions and washes of the smoke

particulates, separations by liquid chromatography, and analysis by GC/MS.

They found many compounds not usually observed In the volatile fraction, e.g.,

aromatic amines and urethanes (expected from the basic decomposition steps

shown In equations 4 and 5), 4 ,4-dlamlnodlphenylmethane compounds and benzoqulnollnes, polycyclic hydrocarbons, nitrogen-containing f Ive-membered ring

compounds. Including Indoles, Isoxazole, Indazole and carbazoles, dlphenylamlne and Its alkyl derivatives, phthalate esters, glycol homologues, and

trlmethyllndole (Table 1). This study indicates the importance of the particulate fraction of the smoke in the examination of the thermal decomposition

products from materials and points out the extremely complex nature of those

products.

3. TOXICOLOGY

Bloassay methods, which expose animals to smoke and toxic gases from the

thermal decomposition of materials, have been used most frequently for

assessing the acute toxicity of fire atmospheres. In most of these tests,

-24-
lethality or incapacitation serve as the biological endpoints; however, more

elaborate methods involving various physiological and biochemical parameters

have also been used. Most procedures include the chemical analyses of

specific toxicants of interest in addition to the animal exposures. Some

early approaches have suggested the use of only the results from the chemical

analyses of specific toxicants. For example, Tsuchiya and Sumi have proposed

a '‘maximum toxicity index" (T^j^) to evaluate the potential danger from toxic

gases produced by combustion of materials [22]. The mathematical model

Ce

proposed is T = 2 — where T =* toxicity index, C ® experimental concentration

Cf

O from a 1 g sample in a 1 m volume, and * concentration dangerous or fatal

to humans in 30 minutes. is the maximum value of T (toxicity index)

obtained from experimental data. When samples of rigid polyurethane foam were

burned at 800 ®C in a glass flask, the production of HCN was found to be

constant (8 mg/g) for sample sizes ranging from 0.4 to 2.4 g, whereas CO and

CO2 concentrations decreased with increasing sample size from 210 to 90 mg/g

and 1400 to 280 mg/g, respectively [21]. Using their toxicity index model,

Sumi and Tsuchiya found that the maximum toxicity indexes were 0.05 for HCN

and CO, and < 0.01 for CO2 at 800°C. Based on these calculations, they estimated that when rigid polyurethane was burned, the same level of toxicity

resulted from HCN and CO. Toxicity due to CO2 was considered negligible. By

Sumi's model, rigid polyurethane has a total toxicity index of 0.10, which is

several times smaller than that of other nitrogen-containing materials such as

acrylic, nylon, wool, and urea-formaldehyde, but is very close to that of

polystyrene and white pine. Such an approach has been considered less reliable than animal data because of the potential additive or synergistic effects

of the toxicants and/or the possibility that unusual toxic products could be

generated and would not be measured with routine chemical analyses.

-25-
The various toxicity test methods have been reviewed in detail by Kaplan

et al. [36]. The main approaches employed to evaluate the acute Inhalation

toxicity of combustion products generated from rigid polyurethane foam are

summarized below.

Biological Endpoints

Method

Lethality Incapacitation Physiological

and Biochemical

Parameters

LC50 No. Animals

Affected

Time to

Death

EC 50 Time to

Incapacitation

NBS** X X

UTAH^ X X

PITtC X X X X X

DIN^ X X X X

JAPAN® X X

uspf X X

^National Bureau of Standards

University of Utah

•^University of Pittsburgh

‘^Method developed in response to the German Commission of Standards

^Methods used by Japanese workers

^University of San Francisco

3.1 National Bureau of Standards (NBS) Toxicity Test Method

The toxlcltles of the thermal degradation products from polymeric

materials, including rigid polyurethane foams, have been evaluated by a number

of laboratories using the NBS toxicity test method [37, 38]. This test method

consists of three components: a combustion system, a chemical analytical

system, and an animal exposure system. The material in question is thermally

decomposed in a 1000 ml cup furnace which is preheated to a temperature either

-26-
25 ®C below the material's autoignition temperature (non-flaming decompostion)

or 25 ®C above the material's autoignition temperature (flaming combustion).

These two conditions, the non-flaming and flaming modes at temperatures close

to the autoignition temperature, are considered worst cases but still

realistic fire conditions. Testing materials under worst case conditions

prevents false negative data. In this case, a false negative result would be

one where the conditions are not optimized to produce the maximum quantity of

toxic materials.

All of the combustion products generated in the cup furnace go directly

into the 200 liter rectangular exposure chamber and remain there (static

exposure) for the duration of the exposure. Carbon monoxide, carbon dioxide,

and oxygen concentrations are monitored continuously, as are the furnace and

chamber temperatures. If the material contains nitrogen, hydrogen cyanide may

also be measured.

Six rats are exposed head-only to the combustion atmospheres in each

experiment. Blood samples are taken from two of the six animals to monitor

the amount of carbon monoxide adsorbed in the blood. Animals are exposed to

the combustion atmospheres for 30 minutes and then observed during a 14 day

post-exposure period. The biological endpoint is the determination of the

LC5 Q - the concentration of material in mg/ 2. that causes 50% of the animals to

die in the 30 minute exposure and 14 day post-exposure observation period. In

this case, concentration is defined as the mass of material (grams) placed in

the cup furnace divided by the volume of the exposure chamber (liters). The

LC50 niay also be calculated based on mass consumed per chamber volume. The

amount of material consumed is obtained simply by weighing the cup before and

-27-
after the 30 minute exposure. The post-exposure observation period is a very

important feature of the NBS toxicity test method since the combustion

products from many of the tested materials have been found to cause extensive

animal weight loss and death during this post-exposure period.

The toxicity of the combustion products from the rigid polyurethane foam

designated GM 29 or 30 obtained from the Products Research Committee (PRC)

[39] has been studied by NBS and two other laboratories which participated in

an interlaboratory evaluation (ILE) of the NBS toxicity test method (Table 9)

[38]. GM 30 is based on a polymeric isocyanate formulation and differs from

29 (samples of which were used by Alarie et al. [45,49,50] and Farrar et

al. [43] in their toxicological studies. Section 3.2 and 3.3) only in the

sample sizes distributed for testing.

Q1 30 appears to be more toxic in the flaming mode with LC^q (30 min + 14

day) values averaging about 12 mg/i compared to more than 34 mg/i found in the

non-flaming mode. (The results of the flaming experiments by Lab 4 shown in

Table 9 did not agree with those of the other laboratories.) In the nonflaming mode, no deaths were observed at the highest sample loadings tested

(more than 39 mg/i).

When compared to Douglas fir and flexible polyurethane foam tested by the

NBS test method (see table below), flaming rigid polyurethane foam GM 30 was

the most toxic [i.e., the LC^q (30 min + 14 day) value of rigid polyurethane

is 13.3 mg/i, whereas, the LC^q of Douglas fir is 40 mg/i and that of flexible

polyurethane foam GM 21 is greater than 40 mg/i]. In the non-flaming mode,

the pyrolysis products of rigid polyurethane foam are less, toxic than those of

-28-
Douglas fir or flexible polyurethane foam whose LC^q (30 min + 14 day) values

are 23 and 27 mg/1, respectively. These values are, however, less than an

order of magnitude different which is not considered toxicologically

significant.

LC50 (30 min + 14 days)

Flaming Non-Flaming

(mg/Z) (mg/Z)

GM 30 13.3 >39.6

Douglas Fir 39.8 22.8

GM 21 >39.6 26.6

One of the ILE participating laboratories (No. 8 ) also used the hind-leg

flexion behavioral avoidance response model [37,40] to monitor incapacitation

and determined EC^q values (the concentration necessary to incapacitate 50% of

the rats during the 30 minute exposures). The results shown in Table 9

indicate that this form of incapacitation occurs at only slightly lower sample

loadings of GM 30 than that necessary to cause lethality [37,38].

Table 10 shows that the percent carboxyhemoglobin (COHb) from exposures

to 30 minute concentrations of flaming GM 30 was 64% and the average

concentrations of CO and HCN in the exposure chamber atmosphere were 1800 ppm

and 140 ppm, respectively. In the non-flaming mode, the value was

greater than 40 mg/Z (l.e., no animals died at concentrations ^ 40 mg/2.) and

therefore, the LC^q gas concentrations are listed as greater than 1700 ppm and

44 ppm for CO and HCN, respectively. Experiments at NBS on the toxicity of CO

in air have shown that 4600 ppm of CO are necessary to kill 50% of the rats in

-29-
30 minutes [41]. This atmospheric CO concentration results In an average

blood concentration of 84% COHb. In the case of rigid polyurethane foam GM 30

in the flaming mode, deaths were observed during the exposure at less than

lethal levels of CO (i.e., the CO concentration was only 1800 ppm and the COHb

was 64%). These results suggest that CO was not the sole cause of death.

Levin et al. have observed that a mixture of CO and HCN act in an addi-

[CO] ^ [HCN] tive fashion, such that if

LC^q CO LC^q HCN

> 1 , the animals will die

[41]. This formula indicates that the CO and HCN concentrations generated at the

^ , , , ,, 1800 ppm CO 140 ppm HCN^

LCjo value of flaming rigid polyurethane (I.e., 4600 ppm CO * 160 ppm HCN ^’

would be sufficient to account for the deaths. Therefore, these results

strongly suggest that the deaths that occurred from flaming rigid polyurethane

GM 30 were due to the combination of CO and HCN.

The toxicity of combustion products generated in the flaming mode from a

sample of rigid polyurethane foam of unknown composition originating from a

jail fire in which 27 people died of smoke inhalation has been tested by Levin

et al. [42]. The LC^q (30 min + 14 days) value for this material decomposed

under flaming conditions was 11 mg/i with 95% confidence limits of 10 to

12 mg/i. This LC^q value is comparable to Chat found for rigid polyurethane

foam GM 30 (14.3 mg/i) exposed to the same conditions [37]. When a sample

loading of the jail material equivalent to a concentration of 11 mg/i was

tested, the average concentrations of CO and HCN were 1160 ppm and 115 ppm,

respectively. The concentrations of these two toxicants are similar to those

found in the GM 30 experiments [37]. According to the NBS studies quoted

above [41] on the interaction of CO and HCN, these two gases were produced in

concentrations sufficient to account for the lethalities observed in the jail

fire.

-30-
3.2 University of Utah Toxicity Test Method

During the development of a protocol to assess the toxicity of combustion

products, Farrar et al. evaluated a series of cellular plastics including the

rigid polyurethane foams Q1 29, (^31, GM 35, 37, and GM 39 from the PRC

collection [43]. This toxicity test method and apparatus upon which the NBS

method was largely based differed from that of NBS in that the University of

Utah test utilized a 60 liter instead of the 200 liter NBS exposure chamber

and used an aluminum cone coated with polytetrafluoroethylene above the cup

furnace to aid in the mixing of gases in the exposure chamber.

The toxicological endpoints were death and incapacitation (determined by

monitoring the hind-leg flexion behavioral avoidance response [37, 40]). EC^q

values were calculated for the 30 minute exposures and LC 5 Q values were calculated from the deaths that occurred during the 30 minute exposures and 14 day

post-exposure periods (Table 11).

Most of these rigid polyurethane foams were more toxic in the flaming

mode [LC 5 Q (30 min + 14 day values) ranged from 10.9 to 16.6 mg/i] than in the

non-flaming mode [LC^q (30 min + 14 day values) were greater than 36.7 mg/Jl in

all cases except for the rigid spray foam formulation (34 39 which had an LC^q

value of 10.9 mg/i]. The presence of an unspecified fire retardant (GM 31)

did not affect the LC^q values. Total mortality, which Included the 14 day

post-exposure deaths, was very close to the exposure lethality for the rigid

polyurethanes studied.

-31 -
According to the data of Farrar et al« , incapacitation (EC^q) occurred at

about the same mass loading per chamber volume (mg/i) for all the tested rigid

polyurethane foams regardless of the combustion mode (flaming or non-flaming)

(Table 11). However, in the interlaboratory evaluation of the NBS toxicity

test method in which seven laboratories examined twelve materials, the EC5 Q

results from the University of Utah were always lower than those found by the

other laboratories who examined the same materials [38]. This may indicate

that another factor in addition to the toxic insult was affecting the incapacitation data. One possible explanation is that the intensity of the shock to

which the animals would respond was set too low. When the animals became

stressed by low concentrations of toxic atmospheres, they would fail to

respond to the electrical shock and appeared incapacitated when, in actuality,

they were not.

Comparison of the LC^q values of these rigid polyurethanes with the

corresponding values found by Farrar et al. for Douglas fir reveals that the

rigid polyurethanes are about twice as toxic in the flaming mode and less

toxic in the non-flaming mode than Douglas fir [43] (see below). In the same

study, LC^q (30 min and 14 day) values for various flexible polyurethane foams

indicate that they were similar or less toxic than the Douglas fir.

-32-
LC50 (30 min + 14 days)

Material

Flaming

(mg/i)

Non-Flaming

(mg/i)

Rigid Polyurethane

CM 21 11,2 >40

CM 31/FR 14,2 >40

CM 35 12,1 >36.7

CM 37 10,9 >36.7

CM 39* 16.6 10.9

Douglas Fir 24.6 14.6

Flexible Polyurethane

CM 21 43.2 13.4

CM 23/FR 34,5 12.6

CM 25 >37.5 36.9

GM 27/FR 33.1 30.5

*foam spray on asbestos cement board

FR: fire retardant

To evaluate the extent to which the CO and HCN concentrations in the

combustion atmospheres generated from the rigid polyurethane foams contributed

to the toxicity of the combustion products, the calculated levels of CO and

HCN at the EC5 Q and LC^q (30 min +14 days) concentrations in the flaming mode

(the most toxic conditions) are shown in Table 12, Based on the studies at

NBS on the toxic interactions of CO and HCN, the LC^q's observed with all the

foams can be attributed to the toxic interaction of CO and HCN [41],

At the University of Utah, Hartzell et al, showed that exposure of rats

to CO alone at concentrations greater than 1500 ppm for 30 minutes caused

incapacitation as indicated by the loss of the hind—leg flexion behavioral

avoidance response [44], Corresponding studies have shown that HCN alone at

concentrations greater than 60 ppm for 30 minutes will also produce incapacitation, The CO and HCN levels in Table 12 range from 610 to 910 ppm and 40 to

-33-
70 ppm, respectively, at the EC^q concentrations. With three of the five

rigid polyurethane foams, GM 29, 31 and 35, the HCN levels alone were sufficient to explain the incapacitation. In the other two cases, the CO probably

played a contributory role.

At the EC^q concentrations, the CO and HCN levels in the non-flaming mode

(690 to 850 ppm and 40 to 75 ppm, respectively) are similar to the levels in

the flaming mode (Table 12) [43]. This is reflected in the closeness of the

EC5 Q values in the two modes of combustion.

3.3 University of Pittsburgh Toxicity Test Method

The toxicity of the thermal degradation products from eight different

rigid polyurethane foams have been evaluated with the University of Pittsburgh

test method [45,47,48,49]. This method is described in detail by both Alarie

et al. [45] and Kaplan et al. [36]. Briefly, this method uses a dynamic flow

system in which materials are decomposed at a steadily increasing temperature

of 20“C/min in a Lindberg furnace. The material is allowed to decompose

initially in a non-flaming mode and to flame when the ignition temperature is

reached. The decomposition products are fed into a glass exposure chamber

(2.3 1) in which four mice are exposed in the head-only mode. An airflow of

11 i/min which is maintained through the furnace is further diluted with cold

air resulting in a 20 i/min air flow through the exposure chamber. Whole body

plethysmographs are used to measure the respiration rate of the mice. For

determination of sensory irritation, 10-minute exposures are used; for all

other biological endpoint determinations, 10 or 30-minute exposures are used.

-34-
This method proposes the use of any of three biological endpoints, all of

which are based on the amount of material placed into the furnace:

(1) Sensory irritation from which an RD5 Q is calculated. The

corresponds to the concentration of smoke which produces a 50%

decrease in the respiration rate of the animals.

(2) Lethality from which the LC

5 Q (the concentration of smoke which

causes 50% of the animals to die during the 30 minute exposure and a

10 minute post-exposure period) is calculated.

(3) Physiological stress from which a "Sensory Irritation Stress Index"

(SI) is calculated [46]. SI values are calculated by a mathematical

approximation which represents the onset, recovery, and degree of

depression of the respiratory rate and includes the corresponding

physiological adjustments, e.g. blood pressure and heart rate. The

SI 100 corresponds to a sample size which produces a 50% decrease in

the stress index (maximum value for SI in these experiments was found

to be about 200 ).

The sensory irritation produced by the combustion products from two rigid

polyurethane foams, based on polymeric isocyanate and polyether polyol (from

sucrose) formulations was examined by Alarie et al. [47]. One of the two

samples contained the fire retardant tris (beta chloroethyl) phosphate. In

this early version of the University of Pittsburgh test method, the furnace

was heated at 25“C/min and the combustion products generated in the furnace

-35-
were pumped through the exposure chamber with an air flow rate that could be

varied from 2 to 100 1/mln. The concentration of the decomposition products

was changed by varying the amount of dilution air. The respiratory rates of

the mice were monitored during the exposures which lasted five minutes beyond

the time that the visible smoke from degradation of the samples disappeared.

The calculated values for the two rigid polyurethane foams were 408 mg

(not fire retarded) and 588 mg (fire retarded). These two RO

5 Q values were

not considered statistically different at a 0.05 level of significance.

However, when compared to the the values found In the same study for a

flexible polyurethane foam with and without a fire retardant, the rigid polyurethane foams were found to be significantly higher and, therefore, consider

ably less Irritating than the flexible foams (data shown below).

RD50 (mg)

Polyurethane FR^ nfr’

Rigid 588 408

Flexible 17 27

^Flre retarded.

^Non-fire retarded.

The combustion atmospheres from both of these rigid foams were examined

by GC and MS and the following volatile compounds were Identified:

acetaldehyde, HCN, ethane, propylene, toluene monoisocyanate , propane,

ethylene oxide, propylene oxide, acetone, and formamlde. The fire-retarded

foam also produced butyraldehyde. These decomposition products represent

chemical asphyxiants and sensory Irritants. Toluene monoisocyanate was

believed to be one of the major Irritants [47].

-36-
The effect of another type of additive, zinc ferrocyanide , on the

toxicity of a rigid polyurethane foam was studied using the version of the

University of Pittsburgh test method described on p. 34 [48]. LC^q values

were determined for a 10 minute exposure plus a 5 minute post-exposure period.

Two samples of rigid polyurethane foam ("PU", untreated; ”PU-A” , 5% zinc

ferrocyanide) were examined. The LC5Q values (10 min + 5 min post-exposure)

were found to be greater than 64 grams (> 320 mg/Z)^ for the "PU” sample and

26.2 grams (131 mg/i) with 95% confidence limits of 22.1 to 31.1 grams for

sample "PU-A". These LC5Q values suggest that the foam treated with zinc

ferrocyanide was more than twice as toxic as the untreated foam. When

compared to other materials tested under these experimental conditions , the

rigid polyurethane foams were significantly more toxic than Douglas fir, which

had a 10 minute LC^q value greater than 460 g (> 2300 mg/il), and less toxic by

at least an order of magnitude than a polychloroprene containing 5% zinc

ferrocyanide, which had a 10 minute value of 2.5 grams (12.5 mg/i). A

flexible polyurethane foam tested under the same conditions was found to have

a 10 minute LC^q value of greater than 100 grams (> 500 mg/Z) indicating a

lower toxicity than the untreated rigid polyurethane.

Using the University of Pittsburgh test method, Anderson et al. also

evaluated the sensory irritant properties and the stress index of four rigid

polyurethane foam samples from the PRC collection (GM 29, GM 31, GM 35, and

GM 37) [49]. All these foams were based on polymeric Isocyanate formulations.

Alarie reports his toxicological results in grams of material. For

comparison purposes the gram units have been converted to mg/2, units by the

following equation:

wt (g)

chamber air flow rate (2,/min) x exposure time (min)

1000 mg/g

-37-
Fluorocarbons were used as blowing agents except for GM 37, in which the

blowing agent was C02» CM 31 contained an unspecified fire retardant.

In these experiments, the air flow through the furnace was 7.5 il/min

through the furnace. Dilution air was added at a rate of 12.5 il/min to

maintain an overall air flow of 20 A/mln through the exposure chamber.

values were based on the respiratory rates of mice exposed for 10 minutes and

followed by a 5 minute recovery period. Stress index determinations were

based on mice exposed for 30 minutes followed by a 10 minute recovery period.

The RO^q values, summarized in Table 13, show no difference in the rigid

polyurethane foams studied. The sensory irritant quality of these foams based

on their RD^q values is comparable to that of Douglas fir (RD^q, 0.14 mg/i).

However, the RD^q values of four flexible polyurethane foams decomposed under

the same conditions were in the range of 0.018 to 0.044 mg/ A, an order of

magnitude more toxic and a difference of considerable Importance. Evaluation

of the materials based on the stress index measure placed the four rigid foams

into a high stress index category, whereas Douglas fir was considered moderate

and the flexible polyurethanes were considered low [49].

Further experimental work on the same rigid polyurethane foams, GM 29, GM

31, GM 35, and GM 37, used a slightly higher ventilating condition (an air

flow of 11 i/min through the furnace) although the total air flow through the

system was still the same (20 i/min) [45]. In addition to sensory Irritation

and evaluation of the stress index, acute mortality (as determined by LC5Q

values for 30 minute exposures followed by 10 minute recovery times), asphyxiation, and histopathology were also examined. Under these experimental conditions, the rigid polyurethane foams started to decompose at about 200“C.

-38-
Foams GM 29, GM 31, and GM 35 never flamed, whereas foam 37 ignited for a

short duration in the 450 to 500®C range. The CO and HCN were released monophasically with peaks occurring about 500 to 525'*C.

The RD5 Q values for the four rigid foams ranged between 0.085 and 0.124

grams (0.42 - 0.62 mg/i) (Table 14) [45]. When compared to the corresponding

RD 5 Q values obtained by Anderson et al. [49] (Table 13), it appears that all

the foams are about half as Irritating (based on respiratory rate depression)

when thermally decomposed with increased ventilation. The RD

5 Q value for

Douglas fir under the same conditions of increased ventilation was 0.034 g or

0.17 mg/il which was 2.5 to 3.5 times more toxic than those observed for the

four rigid foams [45]. The values for flexible polyurethane foams were

an order of magnitude lower than the rigid foams. However, the sensory

irritating effects occurred faster for rigid polyurethane foams than for

Douglas fir and the flexible polyurethane foams. The resulting stress index

values in rigid foams were in the SI 100 = 0.5 to 0.9 grams or 0.83 to

1.5 mg/ i range, which indicates more stress than that found for Douglas fir

(SI 100 = 4.0 g or 6.7 mg/ 2, or for flexible polyurethane foams (SI 100 = 1.3

to 2 g or 2.16 mg/ 2. to 3.3 mg/ 2.) [45].

The LCgQ values calculated from the lethality results following a 30

minute exposure to the combustion products from these rigid polyurethane foams

and a 10 minute recovery period ranged from 7.5 to 10.4 grams (12.5 to 17.3

mg/2,) (Table 14). These LC^q values were comparable to those found for

flexible polyurethane foams [LC^q = 8.3 to 14.4 g (13.8 to 24.0 mg/ 2 )] [45].

Douglas fir, in comparison, was considerably less toxic with an LC 5 Q value of

63.8 grams (106.3 mg/2) [45]. Asphyxiation due to rigid polyurethane foams

occurred at concentrations which ranged from 2 to 8 g ( 3.3 to 13.3 mg/ 2 ).

-39-
Hlstopathologlcal studies, conducted on the animals 24 hours after the 30

minute exposures to the thermal decomposition products of these rigid polyurethane foams showed various degrees of tissue damage In the noses , corneas

,

lungs, and hearts.

In summary, the results of these University of Pittsburgh studies showed

that the thermal decomposition products from the rigid polyurethane foams, GM

29, GM 31, GM 35, and GM 37, were more toxic than wood on the basis of acute

mortality (LC^q values) and physiological stress (SI 100), and less toxic than

wood on the basis of sensory Irritation (RD^q).

Alarle [45] has also attempted to address the acute lethal hazard (ALH)

of materials by taking Into consideration LC^q values, physical properties,

such as the thermal conductivity and density, and the temperature at which the

materials lose 1% of their weight. Although through this mathematical

approach Alarle recognizes that the evaluation of the fire safety of any

material must consider other factors In addition to acute toxicity, this

approach does not address many of the other chemical and environmental factors

which are necessary to consider In a hazard assessment. Using his simple ALH,

Alarle compared rigid polyurethane foams to a glass fiber used for Insulation

purposes. Rigid foams GM 35 and GM 37 were classified as more hazardous than

the glass fiber and foams (M 29 and GM 31 as similar to this glass fiber [45].

Alarle has also proposed a classification of materials based on timeresponse and concentration-response relationships. The calculated LT5 Q values

(the time at which 50% of the animals die after being exposed to concentrations equivalent to the LC^q value for 30 minutes) for the four rigid polyure-

-40-
thane foams were as follows: 28 minutes (GM 29), 23 minutes (GM 31), 17

minutes (GM 35), and 15 minutes (GM 37) [50]. Using this combination of

concentration- and time-response (LCT^q), Alarie et al. showed that all four

of these rigid foams fall into the "more toxic than wood" category [50].

3.4 DIN Toxicity Test Method

The toxicity of combustion products from many materials, including rigid

polyurethane foams, has been evaluated by a number of investigators using

several variations of the DIN method. This toxicity test method (designated

as DIN-Draft 53436) is based on dynamic exposure of rats to decomposition

products generated in the pyrolysis mode in a quartz tube which is heated by

an externally moving (10 mm/min) electric oven. Samples of equal volume or

equal weight per unit length are heated at constant temperatures between 200 °C

and 600*0 in an air stream, which flows countercurrent to the movement of the

oven. The decomposition products are diluted with air and introduced into the

animal exposure chamber (of various designs) to permit head-only or whole body

exposures. Rats usually are exposed for 30 minutes. Toxicity is expressed as

mortality (number of animals affected) which in turn can be related to temperature, airflow, and mass loss, which either fail to produce lethal concentrations or produce an animal mortality of 50 percent (LC^q). The endpoints used

to interpret mortality data under the stated test conditions are:

T^(*C): the temperature which just fails to produce lethalities

(critical temperature)

-41 -
C^(g/A): the decomposition gas concentration which just fails to

be lethal (critical concentration)

the air dilution factor which just fails to provide a

lethal concentration (critical dilution)

T(LC5 q)(‘*C); the temperature at which 50 percent mortality occurs

decomposition product dilution which produces 50

^600(^^50)^S/^)* decomposition product concentration which produces

A detailed description of the apparatus and the application of various endpoints has been summarized by Kaplan et al. [36].

Kimmerle has evaluated the results from toxicity studies of various

materials including rigid polyurethanes using the DIN toxicity test method -

Draft 53436 version [51]. In one of these studies, Effenberg measured the

acute toxicity of the thermal degradation products of a fire retarded rigid

polyurethane foam which was decomposed at 500**C in a specified tube furnace

supplied with air at a rate of 300 i/h. The biological endpoints used to

assess the toxicity of the combustion products were death of the rats, which

were exposed for 30 minutes in a whole body mode, the COHb at death, and the

amount of time that the rats were able to swim before drowning. The pyrolysis

gases from the thermal decomposition of a rigid polyurethane (sample size:

percent mortality at 600 *C

50 percent mortality at 600®C

-42-
100 X 15 X 2 mm) contained 650 ppm CO and 48 ppm HCN. Ten percent (5/50) of

the rats died during the exposure. The COHb level was found to be 24.3%. The

swimming time corresponded to 47 minutes for the rats that survived the

exposure as compared to 93 minutes for the control rats. In similar tests

with spruce wood which produced 5125 ppm CO and no HCN, 69/75 of the animals

died during the exposure, average COHb levels were 47%, and the average time

to drown was 4.2 minutes. The fire retarded polyurethane tested appeared to

be less toxic than the spruce wood [51].

The toxicity of pyrolysis products from two fire retarded (reactive and

additive type fire retardants) and one non-fire retarded commercial rigid MDI

polyurethane foams were evaluated by Kimmerle [51] using the DIN Draft 53436

apparatus. The rigid foam samples were decomposed at temperatures from 300 to

600 "C, a temperature range in which mortalities of animals could be expected.

Strips of foam, either 300 x 10 x 5 mm In size or 1.2 g per 100 mm In weight,

were pyrolyzed in the tube furnace which had an air flow of 100 Jl/h. The

pyrolysis products were further diluted with a 100 Jl/h air supply. Rats were

exposed in a head-only mode for 30 minutes.

Table 15 shows that when standard size strips were pyrolyzed, no

mortalities occurred, except in one experiment with sample 3 at 600“C In which

2/20 rats died. In the series of tests in which samples of equal weight were

pyrolyzed, deaths were not observed below 400 “C. In experiments which

produced lethalities, the CO concentrations ranged from 1900 to 4400 ppm and

HCN concentrations ranged from 75 to 100 ppm. The lethalities were attributed

by Kimmerle mainly to concentrations of CO or HCN or both.

-43-
The toxicity produced by the thermal degradation of rigid polyurethane

foams was compared to that from a conventional material (spruce wood) tested

under equal surface area conditions. The lowest decomposition temperatures at

which deaths were observed were 600“C and 350®C for standard size strips of

rigid polyurethane (No. 3) and spruce wood, respectively. Based on these

results, Kimmerle concluded that the pyrolysis products from these rigid

polyurethane foams were less toxic than those of wood [51].

The extent to which rigid polyurethane foams can pose a toxic threat in

real fires was further examined by Kimmerle and Prager [52]. In this second

study, the effects of variable characteristics of a fire were estimated by

varying the concentration of decomposition gases with different air dilutions

as well as varying the pyrolysis temperature between 300 and 600 **0. Two MDI

type polyurethanes ("PUR 1” - non-fire retarded and "PUR 2” - treated with a

reactive flame retardant) were used. For "PUR 1", the following toxicological

values were determined:

T^ = 400-450“C

c T (LC50) = 425“C

^600 (LC50) = 1100 t/h

LC5Q (600“C) =» 6.6 mg/t

LC5Q (500“C) - 7.5 mg/i

LC50 (400“C) =« 29 tng/il

A comparison of these T^ and 1(10^0 ) values to those of spruce wood

[Tj. =» 350-400"C; T(LC5q) = 375“C] suggests that the relative toxicity of

decomposition products from "PUR 1" is less than that of wood. However, the

-44-
DsooCLCsq) and LC5o(600“C) values show that "PUR-1” products produce greater

toxicity than those of wood [ 0500 ^^^50 ^ “ ^/h; LC5 q( 600 ‘*C) =

29 mg/i). The limited amount of toxicity data for the fire retarded polyurethane sample, "PUR-2", did not show conclusively whether the toxicity was

influenced by the presence of the fire retardants.

By comparing the toxicological results of rigid polyurethane to those of

other nitrogen-containing materials under the same test conditions, Kimmerle

and Prager also demonstrated that toxicity is not necessarily dependent on the

nitrogen content of the material. For example, both flexible and rigid polyurethane contain about the same amount of nitrogen in the formulations (3 to

6 Z), but the T (LC^q) and D^qqCLC^q) values for flexible polyurethanes were

found to be about 600 and 100-300 A/h, respectively, which makes them appear

slightly less toxic than rigid pol3nirethanes. Whereas nylon and wool, which

contain about twice as much nitrogen as polyurethanes (11 to 12% and 13 to

14%, respectively) have T (LC^q) and DgQQ(LC5o) values of 500 to 600“C and

100-200 i/h (nylon) and 450 to 500“C and 900 l/h. (wool). Thus the hazard

based on toxicity of combustion products cannot be evaluated on the basis of

chemical composition alone.

Herpol used the DIN method to evaluate the toxicity of the combustion

products from fire retarded and non-fire retarded materials, including rigid

polyurethane foams [53,55]. These studies were designed to estimate the

contribution of toxicity to total fire hazard. In one study, samples of a

self—extinguishing rigid polyurethane foam (K14), coated with asbestos on both

sides, were degraded at three different temperatures, 400, 600, and 800 °C

[53]. An air flow of 200 Z/h was maintained through the furnace and the

-45-
combustion products in the exposure chamber were further diluted with an

additional air flow of 200 il/h. Rats were exposed in a whole body mode for 30

minutes and lethality (as measured by the cessation of respiration) was the

biological endpoint. In the second study, a pair of polyether type polyurethane foams (K5 - not fire retarded and K6 - structurally selfextinguishing) were decomposed at 500, 600, and 700®C [55].

The results from both studies are shown in Table 16. The only

lethalities noted for sample K14 occurred at 600°C. For sample K5, deaths

occurred at 500 and 700 **0, and for sample K6, deaths occurred at all three

temperatures. For sample K14, the CO and CO2 indexes (i.e., integrated

concentrations for the test period) at 600®C were 143,430 ppm-min and 30.8

percent-mln, respectively. (These values correspond to average concentrations

of 4780 ppm CO and 1.03% CO2 [53].) These results are in agreement with

earlier work [54] on mixtures of CO and CO2 in which Herpol et al. noted that

deaths first occurred at a CO index of 120,000 ppm-min and 100% mortality

occurred at 210,000 ppm-min. They also found that at a CO2 index of 75

percent-min, respiration rate increased and reached a maximum at 150

percent-min; at 300 percent-min, inhibition of respiration occurred.

For samples K5 and K6, the CO and CO2 Indexes in experiments causing

deaths ranged from 27,300 to 124,800 ppm-min and 57.0 to 162.0 percent-min,

respectively. The wide scatter in the production of CO and CO2 was thought to

be caused by the heterogeneous flaming behavior of these materials.

According to Herpol , COHb levels in the blood of the dead animals exposed

to the decomposition products from these samples of rigid polyurethane foam

-46-
appear to be Insufficient (42 to 64%) to be the sole cause of the deaths

[53,55]. Other toxicants are also contributing to these deaths. Although

CO

2

, at the levels produced in these experiments, generally acts to increase

respiration rates, the effect seen in these studies was an inhibition of

respiration, an additional indication of the presence of other toxicants.

To estimate the hazard to life of a material, Herpol proposed the use of

the "toxicity index" (TX) , which is derived by the mathematical expression:

TX

I k

where m^ = observed mortality at time i and = "penalization" factor. A

good correlation was shown to exist between TX and LT^q values (the time

necessary to cause 50% mortality). The TX value for the self-extinguishing

rigid polyurethane foam (K14) was 18.00 at bOO^C, which places it in the lower

50% of the range of values found for the materials studied [53]. The maximum

TX values for the untreated (K5) and self-extinguishing polyurethane foam (K6)

were 75.7 (700"C) and 44.4 (500“C), respectively, which are in the upper 50%

of the range of values [55]. Foam (K6), however, appeared to be less

dangerous than the non-fire retarded polyurethane foam (K5) based on a "global

toxicity index” (an expanded mathematical model of the TX developed by

Herpol)

.

A modified version of the DIN 53436 was used by Purser and coworkers to

study the incapacitation effects from the thermal decomposition products of a

rigid polyurethane foam (whose formulation was based on MDI) [56,57]. The

rigid foam was introduced into the tube furnace at a constant rate of

-47-
3.2 mm/min and was decomposed in non-flaming mode at 600®C under flow of air

(1 i/min). The combustion products were diluted further with air in a mixing

chamber. C3mamolgus monkeys were exposed for 30 minutes to various sublethal

atmospheric concentrations (supplied to the monkey's face mask via a pneumotachograph). Respiration, electrocardiography (EGG), blood levels of toxic

gases, electroencephalography (EEG), and peripheral nerve conduction were

monitored. Onset of incapacitation was estimated by changes in various

physiological signs. Atmospheres containing concentrations of HCN first

caused an Increase in respiration followed by a decrease and ultimately semiconsciousness. This was accompanied by a depression of EEG signs, a decrease

in heart rate and a change in the EGG waveform.

When 1.83 mg/i of the rigid polyurethane foam was degraded under nonflaming oxidative conditions at 600 ®G, 1187 ppm GO, 2467 ppm GO2 and 108 ppm

HGN were generated. The average incapacitation time was 23 minutes. The

venous blood GOHb levels at the end of the 30 minute exposures were in the 17

to 28% range and the blood cyanide levels ranged from 71 to 81 ymol/i (1.8 to

2.1 Ug/mi) range. A statistically significant relationship was found between

the HGN concentration and the time of incapacitation. By comparing the toxicological results produced by the combustion products of rigid polyurethane

with those of other materials studied. Purser noted that the toxicological

signs were very similar to those produced by pure HGN in air or by the combustion of flexible polyurethane or polyacrylonitrile. Therefore, Purser and

coworkers attributed the narcotic and toxic effects produced by the pyrolysis

of the rigid polyurethane foam to HGN despite the fact that many other

chemical species were also generated.

-48-
3.5 Japanese Combustion Toxicity Tests

The Japanese research groups have used various test methods to evaluate

the toxicity of combustion products. In most cases, these tests are

characterized by dynamic systems and time-based biological endpoints. In this

section, the methodology and the results of the experiments that have been

used in the evaluation of rigid polyurethane foams will be described.

The toxicity of fire gases from building insulation materials, including

rigid polyurethane foams (some of which were fire retarded), was evaluated by

Saito [58]. A burning wood crib was used as the ignition source in his

combustion chamber. The system was designed to simulate actual fire conditions in a semi-closed room. Three rigid polyurethane PAPI based foams (RF-A,

untreated; RF-B, treated with a reactive phosphorus-containing polyol fire

retardant; and RF-C, treated with a nonreactive fire retardant tris-2-chloroethyl phosphate), were mounted on one wall and the ceiling and were subjected

to the flames and radiation from the burning wood crib. Air was supplied to

the combustion chamber at 12 i/min for the first 6 minutes of the experiment.

After 6 minutes, the rate of gas evolution from the burning material decreased

considerably and the air flow was decreased to prevent dilution of the gas

concentrations in the exposure chamber. Mice were placed in rotary cages in a

separate exposure chamber and were exposed in the whole body mode to the

combustion products for 20 minutes.

The toxicity of the fire gases was evaluated by three indexes: (1) the

LT^q, the time for 50% of the test animals to become incapacitated as indicated by collapse of the mice, (2) the arithmetic mean incapacitation time

-49-
(X), and (3) Tg, the specific gas toxicity which is based on the weight of

sample consumed and the collapse time of the animals.

Two sets of experiments were done. In the first series of experiments

samples weighed 27 to 28 g and had a surface area of 300 cm and the volume of

the exposure chamber was 125 I, The CO concentrations in the exposure box

exceeded 10,000 ppm for all three foams. Replicate experiments showed that

the evolution rate and maximum concentration of HCN (as measured in the

connecting pipe between the combustion and exposure chambers) varied for the

three materials: sample RF-A generated 72 to 96 ppm in the first two minutes

after which the concentration decreased until it could not be detected at

6 minutes; sample RF-B generated 72 to 130 ppm at 4 minutes; and sample RF-C

generated 121 to 138 ppm at the end of the 6 minute period.

In the second series of experiments, only samples RF-A and RF-B were

used. The specimen area was Increased 1.5 times and the exposure chamber 4.8

times. CO concentrations decreased to 4100 ppm and 3700 ppm for rigid polyurethane samples RF-A and RF-B, respectively. The maximum HCN concentrations,

328 ppm (RF-A) and 710 ppm (RF-B), were generated in the first 2 minutes.

The animal results, mean Incapacitation times, LT^q values, and the

toxicity indexes, from both sets of experiments suggest that under these

conditions the treated and untreated foams generate products of about equal

toxicity (Table 17). When the results of the two series were compared to

those from wood and flexible polyurethane foam decomposed under similar experimental conditions, both the untreated and the fire retarded rigid polyurethane foams were found to be less toxic than plywood but about as toxic as

-50-
flexible polyurethane foams. Salto suggested that the HCN generated from

polyurethane foams Is consumed In a secondary combustion stage and the major

toxic gas in actual fires is CO.

Kishitanl used a tube furnace to determine the toxicity of combustion

products from a rigid polyurethane foam as well as from other building

materials [59]. The furnace was heated gradually from room temperature to

740®C in 15 minutes. Air flow through the furnace and exposure chamber was

maintained at 2 Jl/min. One mouse at a time was exposed in a whole-body mode

to the combustion products from 3 g of the foam. The biological endpoints

examined were changes in the electrocardiograms, blood COHb concentrations,

and time of death.

In two experiments, flaming occurred at about 8 minutes. In three other

experiments, the time of initial flaming was not measurable. Four out of five

mice died within 15 minutes, with an average time to death of 14.44 minutes.

One mouse died 1.5 min after the exposure. The presence of harmful fire gases

was evident from electrocardiograms which showed abnormalities at 7 to 8

minutes. The average COHb concentration in the blood was 24.3%. Since in

baseline studies with pure CO, Kishitani found that the lethal concentration

of COHb in mice was 35 to 40% [59], the COHb levels found in these experiments

are below the lethal concentration and are indicative that other toxic gases

besides CO existed in the combustion atmosphere [59].

In a second investigation, Kishitani and Nakamura studied the toxicity of

combustion products from building materials decomposed at 350, 500, and 750“C,

the temperatures to which materials are normally exposed in the early stages

-51 -
of fires [60,61]. Materials were heated in a quartz tube furnace. One mouse

at a time in a whole-body mode was exposed to the combustion products in an

adjacent chamber. A vibration detection device was used to monitor movement

of the test animal. Time of death, as indicated by cessation of respiration

or loss of movement, was noted as the end point. The average maximum concentrations of CO and HCN in the exposure chamber produced by the decomposition

of 5 g samples were 3700 ppm and 45 ppm at 350®C, 6100 ppm and 126 ppm at

500“C, and 3200 ppm and 52 ppm at 750®C, respectively. From the combustion

studies presented in section 2.2. 1.1, one would expect CO and HCN to increase

with higher temperatures. Kishitani and Nakamura's results do not show this

trend. The reason for this inconsistency is unclear. All lethalities

occurred during the 500®C exposure (at 8.67, 12.67, and 14.25 min), during

which the highest concentrations of CO and HCN were generated. A good correlation was found between the time of death of the mice, the concentration of

HCN, and the temperature at which the highest HCN was produced. The authors

concluded that the toxic effects of the combustion products from rigid polyurethane foam depended mostly on the presence of HCN and to lesser extent on

CO [60,61].

Kishitani and Yusa examined the toxicity of combustion products from a

rigid polyurethane foam at 850 “C [62,63]. In these experiments, a vertical

tubular furnace was used and the whole bodies of five mice were exposed simultaneously in revolving cages. In addition to visual observation of the mice,

the revolution of the cages was monitored by electrical pulses. The time that

the mice collapsed, as indicated by stoppage of the revolving cage, was

considered the endpoint. The exposure lasted until all five mice collapsed

but did not exceed 15 minutes. The results in Table 18 indicate that the

-52-
maximum CO concentration varied from 600 to 800 ppm, regardless of sample

size. The maximum HCN concentration varied from 52-124 ppm and was increased

with sample size. The toxicity of combustion products from rigid polyurethane

foam decomposed at 850 “C was found to be about six times greater than those

from Japanese cedar and lauan studied under the same conditions.

3.6 University of San Francisco (USF) Toxicity Test Method

Hllado et al. have evaluated the relative combustion product toxicity of

many commercial products, including rigid polyurethane foams, using the

University of San Francisco test method. This test method involves exposing

f four freely moving mice in the whole-body mode until death or for a maximum of

30 minutes to the thermal degradation products from 1 g samples decomposed in

a tube furnace heated at either increasing or constant temperatures.

Biological endpoints are time to incapacitation as indicated by staggering,

prostration, convulsions, and collapse, and time to death as indicated by

cessation of movement and lack of respiration.

The effect of flame retardants on combustion product toxicity was

considered of special interest. Three rigid polyurethane foams, based on a

propoxylated aromatic amino polyol formulation, were thermally degraded in a

tube furnace at a rising temperature rate of 40*C/min from 200 to 800 ®C [64].

The first foam (Rl) was untreated, the second foam (R2) contained 10% of a

chlorinated butylene oxide-based polyol fire retardant, and the third foam

(R3) contained 7% of FYROL 6^ fire retardant. As seen from Table 19, times to

incapacitation and death were not affected significantly by the presence of

these fire retardants.

-53-
Preliminary toxicological screening tests also were conducted with a

fourth rigid polyurethane foam based on a polymeric isocyanate and propoxylated trimethylolpropane formulation containing 16% of FYROL 6^ [65]. This

type of formulation had been reported to be unusually toxic when thermally

degraded [32,66]. Under the same experimental conditions as previously

described, except that the starting temperature was ambient and, in some

tests, the maximum temperature was SOO^C, no deaths were observed during the

30 min exposures when the upper temperature limit was 500“C (Incapacitation,

however, occurred at 9.5 min). Increasing the upper temperature limit to

800 ®C increased the toxicity of the degradation products, as indicated by the

death of all mice within 20 minutes. The average incapacitation time (T^) was

12.91 ± 1.92 min and the average time to death (T^) was 15.73 ± 0.90 min.

This mean and standard deviation was calculated for the mean times of three

repeated experiments. Standardization of the furnace temperature profile

(heating at 40**C/min from 200 to 800*C) did not change the mortality

appreciably. All mice still died within 20 minutes and the average T^ and T^j

times were only slightly less, at 11.23 ± 0.50 and 14.05 ± 0.60 min,

respectively [65]. With this test method, this material does not appear to be

any more toxic than the other FYROL 6 rigid polyurethane foam that was tested

by Hilado and Saxton, the data for which are given in Table 19.

In a subsequent study, the same four rigid foams were reevaluated to

compare the toxicity of decomposition products generated by the rising temperature program (40®C/min from 200 to 800®C) to those generated by a fixed

temperature program at 800“C [67] (Table 20). In this study, concentrations

of CO and methane (CH^) were also measured by GC.

-54-
Hllado and Machado found that the constant temperature program (800 ®C)

markedly reduced the time of incapacitation and time to death of the animals

(Table 20). This is attributed to the more rapid rate of generation of the

toxic degradation products at 800®C. However, even though the CO may be

generated more rapidly at 800 “C, the mean CO concentrations for R1 , R2 , and R3

are lower when the foams were decomposed at 800 ®C than when they were heated

gradually at 40°C/min. The mean CH^ concentrations are not significantly

different between the two temperature modes. These results indicate that CO

and CH^ are not the only gases responsible for the observed biological effects

for those three foams.

In an earlier study by Hilado and Cummings [68], mice were exposed to CO

gas in air and 6000 ppm CO produced deaths in about 8 minutes and 10,000 ppm

CO caused deaths in 5 minutes. When the rigid foams R1 , R2, and R3 were

decomposed at 800*C, the mean CO concentration was about 2500 ppm and deaths

occurred at 8 to 9 minutes, which is earlier than expected by the CO concentrations alone. On the other hand, foam R4 produced a mean CO concentration

of 6000 ppm and the animals died in one case at 24 min and in the other, at 12

min. These times are 16 and 4 minutes later than expected from the CO experiments alone. These data indicate that the deaths from samples R1 , R2 and R3

are not due to CO alone. R4 produced enough CO to cause the deaths , but the

time delay may be indicative of the unpredictability and variability in the

test method.

Included in Table 20 also are T^ and T^j measurements for two other flame

retarded rigid polyurethane foams, samples SI and S2, which were decomposed

with the rising temperature program [69]. The Tjj^ times were somewhat longer

-55-
and times shorter than those for the foams R1 to R4. Because of the range

in times to Incapacitation and death from the decomposition products of these

six rigid polyurethanes, Hllado et al. suggest that there Is no "typical" or

"representative" level of performance for rigid polyurethanes foams.

In his studies with rigid polyurethane foams, Hllado noted that the rigid

polyurethane foams exhibit decreased toxicity upon aging. Longer times to

death than those obtained In the earlier studies under the same experimental

conditions were observed at later dates (Table 21). For example, time to

death for rigid polyurethane foam R4 Increased In seven months from 14.05 min

[65] to 23.52 min [70] and then changed further after 15 months to 24.93 min

[67]. Times to death for three foams Rl, R2, and R3 also Increased about 10

minutes over a two year period. Hllado attributed the decrease In toxicity to

changes that occurred In the foams upon storage - such as continuation of the

crosslinking process, oxidation, and loss of volatiles. Although the effect

of material aging on toxicity Is an Important Issue to Investigate, It Is not

clear whether the time differences reported here are toxlcologlcally significant. There certainly Is no difference between 23.5 and 24.9 min.

Hllado and Machado also attempted to determine whether a correlation

existed between the concentration of CO generated, the amount of char

produced, and the times of death [71]. They made the following assumptions:

(1) fraction of carbon oxidized to CO2 Is negligible under pyrolytic static

conditions because of Insufficient O2

, (2) the fraction of carbon converted to

smoke particles Is negligible because of little visible smoke formation, and

(3) the residual char and CO produced theoretically represent the total carbon

content of the material. Therefore, CO would be the primary toxicant and an

-56-
increasing char yield would correspond to lower CO concentrations and lower

toxicity as indicated by increased times of death. The char yields, times to

death, and the highest CO concentrations measured when the rigid polyurethane

foams Rl, R2, R3, and R4 were decomposed under the fixed and rising temperature programs are shown in Table 22. With the rising temperature program, the

maximum CO concentrations decreased somewhat with increasing char yield, but

the times to death were about the same. However, with the fixed temperature

program at 800 "C there was no correlation between the amount of char and the

amount of CO or between the amount of CO and the time to death. Again, it is

not clear from Hilado's data whether these differences in time are toxicologically significant or even statistically significant since he never gives the

within experiment variability, only the between experiment variability.

Except for R4, the CO concentrations alone were too low to be the

principal toxicant at the time of death in the fixed temperature program

[68] . A slight increase in times to death, with the exception of sample R4,

was noted as the char yield decreased. The data suggest that, at dOO^C, the

increased relative toxicity observed with increasing char yield for rigid

polyurethane (contrary to the trend observed for other groups of polymers)

indicates that other volatile compounds (e.g., HCN) may be contributing to the

toxicity of the pyrolysis gases [71].

The effects of temperature on the toxicity of the combustion products was

further investigated by Hilado’s group to see whether the rising temperature

method can produce the same toxicity as observed from the average of the

successive fixed temperatures [72]. Samples of a urethane-type rigid foam

were decomposed at fixed temperatures from 200 to 800“C at 100°C intervals and

-57-
also with the rising temperature program at 40*C/mln starting at 200*0 and

ending at 800 “Ce This series of experiments was conducted both with no forced

air flow and with a one ^./min air flow. Toxic effects, as observed by time to

staggering, time to convulsions, and time to death were estimated by summation

of all the times to the effects at successive fixed temperatures. The arithmetic averages of all the mean times to toxic effects at six fixed temperatures (300 to 800*C) and the corresponding times obtained using the rising

temperature program are given in Table 23. In all cases, the calculated

average times to incapacitating toxic effects and to death (survival time) at

the fixed temperatures were 10 to 20% greater than those found during the

experiments with rising temperatures. Less CO was produced under the rising

temperature conditions than the calculated average of fixed temperature experiments for both series of experiments, with and without forced air flow.

Again the experiments with less CO seem to produce faster times to incapacitation and death if these times can be considered significantly different.

Experiments performed with a 1 H/min forced air flow produced shorter times to

effects than those without forced air. It appears that toxicity of rigid

polyurethane is about the same when estimated by the rising temperature

program of the University of San Francisco test method or by combined

successive fixed temperatures.

In the course of his studies, Hilado evaluated a variety of materials and

determined the relative toxicity using the USF toxicity test method. When the

toxicological results of rigid polyurethane foams are compared to those of

cellulose materials, evaluated by the rising temperature program (200 to

800“C, no forced air flow), rigid polyurethanes (Rl, R2, R3, and R4) appear to

be less toxic than wood. Average times to death for the four rigid polyure-

-58-
thanes range between 23 and 26 minutes as compared to times to death of 13 to

16 minutes for seven wood species [73]. The difference in relative toxicity

of rigid polyurethanes and wood is less when the materials were evaluated with

the fixed temperature program (800®C, no forced air flow). The average times

to death for the same polyurethanes varied from 7 to 13 minutes as compared to

6 to 7 minutes for five wood species [74]. To determine the significance of

these numbers, it would be necessary to know the within experimental variation, which is not given.

3.7 Miscellaneous Studies

3.7.1 University of Michigan Tests

A small-scale test procedure to investigate the toxicity of combustion

products from polymeric materials was devised by Hartung [75]. The experimental procedure involves exposing rats in a whole body mode to the thermal

degradation products generated by a radiant heat source in a static exposure

system and determining the time to incapacitation by observing when the rats

were no longer capable of maintaining their balance on a rotating rod located

above an electrified grid and remounting the rotarod within 2 minutes after a

fall.

Three and one-half gram samples of three rigid polyurethane foams

(A,C,D), based on a THERMOLIN RF-230 formulation with different additives,

were thermally decomposed under nonflaming conditions at a radiant heat flux

of 3.2 W/cm . Four rats were placed in separate chambers in an adjoining

exposure box and were exposed to the combustion products. CO2 and CH^ were

-59-
analyzed in the exposure box atmosphere by GC, CO was examined by GC and NDIR,

HCN and HCi were detected by specific-ion electrodes, and the oxides of

nitrogen and acrolein were measured by a colorimetric technique. Gas and

toxicological results from two tests were averaged and are summarized in

Table 24.

The mean times to incapacitation were very similar for samples C (spray

type) and D (slabstock), 28.16 and 28.48 min, respectively. Sample A (pourin-place) produced an incapacitation time of 39.5 min, which was shown to be

statistically significantly longer compared to the times of samples C and D.

The reduced toxicity of the combustion products from Sample A is attributed to

the lower production of CO, HCN, and HCl as compared to the yields from

Samples C and D.

Douglas fir, under the same conditions, produced a mean time-to-incapacitation of 27.06 ± 2.39 minutes. Differences between the more toxic rigid

polyurethane samples C and D and Douglas fir were not statistically different.

3.7.2 Mechanistic Studies of HCN and CO Toxicity

The cardiotoxic effects of multiple acute exposures to the pyrolysis

products of rigid polyurethane foams were studied in rats and the relative

contributions of CO and HCN to the cardiotoxicity were evaluated. Rats were

exposed to one of several experimental atmospheres: polyurethane smoke or

hemlock smoke generated at 500°C, both with or without added CO at various

concentrations, or CO at a concentration of 2350 ppm in air [76]

.

The exposures were conducted in head—only mode in a flow-through exposure chamber and

-60-
lasted for 10 to 20 minutes. Cardlo toxicity was documented by creatine

phosphokinase activity (CPK/MB), ectopic beat frequency following norepinephrine stress and the incidence of myocardial lesions. A positive correlation

was found between the level of CPK/MB activity and the duration of exposure,

as well as the concentration of atmospheric CO during prolonged exposures.

Similarly, the number of ectopic beats produced by groups of four animals

increased as the CO concentration and/or the duration of exposure in each

experimental atmosphere increased. Microscopic examination of cardiac tissue

revealed acute lesions, some of which were under repair. The rats exposed to

polyurethane smoke had a higher CPK/MB activity than did those rats exposed to

CO in air at comparable concentrations of CO. The same phenomenon was

observed with the ectopic beat measurements. These data strongly suggest that

CO cannot fully account for the observed degree of cardiOtoxicity induced by

polyurethane pyrolysis products. Apparently, a pyrolysis product other than

CO or in addition to CO must be partly responsible for the excessive cardiotoxiclty observed upon exposure to polyurethane pyrolysis products. This

excessive cardiotoxicity was not observed upon exposure to the pyrolysis

products of hemlock.

The implication of HCN as the other responsible pyrolysis product was

t tested [77 J. Using a similar experimental protocol, rats were exposed to test

atmospheres with or without supplemental CO and/or HCN. The addition of HCN

to the various atmospheres resulted in an increase in both the CPK/MB activity

as well as the number of ectopic beats induced by norepinephrine stress. The

cardiotoxic effects of HCN were further substantiated by the protection

afforded by the administration of the cyanide antagonists chlorpromazine and

thiosulfate prior to exposure to the test atmospheres. It is apparent that

-61 -
HCN contributes to the production of cardlotoxlclty observed when animals are

exposed to an atmosphere of combustion products from rigid polyurethane foam.

The molecular mechanism potentially responsible for the toxicity of

polyurethane pyrolysis products was Investigated by Thomas and 0* Flaherty

[78]. The In vivo Inhibition of cytochrome _c_ oxidase was measured following 5

min Inhalation exposures of rats to rigid polyurethane combustion products

(generated at 500“C). The HCN present In the atmosphere was responsible for

the noncompetitive Inhibition of heart and brain cytochrome c_ oxidase. The

magnitude of the In vivo Inhibition correlated with the measured blood cyanide

level. The blood cyanide levels responsible for 50% Inhibition of cytochrome

c^ oxidase In the brain and heart were nearly equivalent, 0.26 Ug/ml and

0.29 Ug/mil, respectively. Inhibition of hepatic cytochrome c_ oxidase was

variable. Since these values of the fatal blood cyanide levels measured In

rats exposed to pyrolysis fumes from rigid polyurethane are similar to those

recorded for some human fire victims [79], cytochrome ^ oxidase Inhibition In

critical tissues Is likely to be one of the molecular mechanisms contributing

to the ultimate responses of incapacitation and death following exposure to

the combustion products of rigid polyurethane foam.

3.7.3 Production of Unusual Toxicity

In most of the studies examined for this review, there have been no

significant differences noted between the toxicities of the thermal decomposition products from fire retarded and non-fire retarded rigid polyurethane

foams. However, as noted earlier in section 2. 2. 1.4, an unusual toxic effect

was observed when animals were exposed to the combustion products from a

-62-
laboratory formulated rigid polyurethane foam based on a propoxylated

trimethylolpropane (MW 340) and polymethylene polyphenyl isocyanate containing

the reactive fire retardant 0 ,0-diethyl-N,N-bis (2-hydroxyethyl)-aminomethyl

phosphonate (4 to 8 weight percent) [32,66,80]. When this fire retarded foam

was irradiated by a radiant heat flux of 5 W/cm in the NBS smoke chamber, the

non-flaming thermal degradation products produced grand mal seizures and death

in rats following a 20 minute exposure [32]. The grand mal seizures occurred

in the rats during the first hour following the exposure to smoke from this

particular fire-retarded polyurethane foam. Additional physiological changes

included alterations in the respiratory response to smoke irritants, high

amplitude spike discharges in the EEC, and blood COHb levels of approximately

6%. However, cardiac arrhythmia was not observed. Control animals were

exposed to 1500 ppm of CO, wood combustion products or the corresponding nonfire retarded foam, but these abnormal neurological effects occurred only

following exposure to the fire retarded foam (Table 25). None of the foams

tested (fire retarded or non-fire retarded) produced debilitating COHb levels

(levels ranged from 5 to 33% COHb).

As noted earlier, these toxicological effects were attributed to the

presence of 4-ethyl-l-phospha-2 ,6 ,7-trioxabicyclo [2.2.2] octane-l-oxide

(commonly referred to as a bicyclic phosphate ester) in the combustion atmoshperes. Bicyclic phosphate compounds have been shown to cause seizures at

very low concentrations [81].

The acute inhalation toxicity of this bicyclic phosphate ester generated

as an aerosol was measured in rats by Kimmerle [82], who also noted seizures

of varying severity. In addition, the unusual toxicity of the thermal decom-

-63-
position products from this same fire retarded rigid polyurethane foam was

confirmed by Potts and Lederer using the screening method developed by the Dow

Chemical Company for evaluating potential smoke toxicity [80]. In this test

method, rats were exposed In the whole body mode to products generated under

non-flaming conditions In a quartz cup furnace and deaths were noted at

significantly lower levels than when other celluloslc materials were

decomposed under the same conditions. For example, a two gram sample of the

blcycllc phosphate ester fire retarded rigid polyurethane foam affected 7/7

rats, whereas 0/7 rats were affected In the case of fir plywood. Rats also

were noted to experience violent seizures just before death. However, when

this formulation of rigid polyurethane foam was decomposed In the flaming

mode, no unusual toxicity was noted and the lethalities occurred In the same

concentration range that was found for fir plywood.

Keller et al. also studied this foam along with six other fire retarded

polyurethane foams (Table 26) [66]. Rats were exposed to the combustion

products from these fire retarded foams which were pyrolyzed at a heat flux of

5 W/cm in the NBS smoke chamber. Sample 1 was similar to the blcycllc

phosphate ester producing foam used by Petajan et al. [32] except it contained

16% of the fire retardant. Sample 2 was based on the same polyurethane

formulation, but contained 18% of the commercial phosphate flame retardant

known as VIRCOL 82. Samples 3, 4, 5, and 6 were based on an amine polyol

formulation and contained 0 to 30% of the fire retardant, ANTIBLAZE 19.

Sample 7 was based on trlmethylolpropane polyol (similar to foam investigated

by Petajan, et al. [32]) and contained 10% ANTIBLAZE 19. ANTIBLAZE 19 is a

phosphorus-containing derivative of trlmethylolpropane and the possibility

existed of its conversion to the toxic blcycllc phosphate ester when thermally

-64-
decomposed. Keller's results showed that the nonflaming decomposition

products from both rigid polyurethane foams 1 and 2 caused convulsive seizures

and deaths of the exposed rats either within the 20 minute exposure period or

soon thereafter.

Rats exposed to products involving Antiblaze 19, with the exception of

foam sample 6, did not exhibit any seizure type effects but showed normal

behavior through the 14 days post-exposure period. The p3n:olysis products

from sample 6 caused the post-exposure deaths of 5/8 of the tested rats, but

no signs similar to those caused by bicylic phosphate ester were observed.

Thus, the addition of the fire retardants 0,0-diethyl-N,N-bis

(2-hydroxyethyl)-aminomethyl phosphonate and VIRCOL 82 produced the neurological toxic effects but the fire retardant ANTIBLAZE 19 did not produce

these unusual toxic effects.

The relative toxicity of combustion products of a trimethylolpropanebased rigid polyurethane foam containing various other types of phosphorus

additives was investigated by Wright and Adams under flaming and non-flaming

conditions [83]. The exposure and sample decomposition system was similar to

that of Petajan et al. [32]. Foams were formulated to contain 16% of the

following phosphorus additives; 1) a brominated phosphate ester, 2) a

reactive phosphonate, 3) a polymeric chlorinated phosphonate, 4) a chlorinated

phosphate ester, and 5) an inorganic polyammonimum phosphate.

The toxicological results, summarized in Table 27, show that, with the

exception of the brominated phosphate additive, mortalities occurred when all

trimethylolpropane-based rigid foam formulations with phosphorus additives

-65-
were thermally degraded under nonflaming conditions. When the trlmethylolpropane-based rigid foams were decomposed In the flaming mode, a marked reduction In the toxicity of the combustion products was observed. Mortalities

were observed only when the foams with the chlorinated phosphonate and polyammonium phosphate additives underwent flaming combustion. When the same

phosphorus additives were used in sucrose based - instead of trimethylolpropane-based rigid polyurethane foams, no mortalities occurred from exposure

to the nonflaming combustion products (not shown in Table 27).

Relative toxicity studies of the type of rigid polyurethane foam reported

to be unusually toxic [32] were also conducted by Hilado and Schneider using

the University of San Francisco toxicity test method [70]. The formulation of

their foam was based on polymeric isocyanate and trimethylolpropane with a

hydroxy number of 550 and contained the fire retardant FYROL 6^. No unusual

toxicity was observed when the tests were performed in absence of a forced air

flow regardless of whether the material was decomposed under an increasing

temperature program or at a fixed temperature of 800“C. Convulsions and

seizures were observed when the fire retarded rigid polyurethane was pyrolyzed

at 800®C in the presence of a forced air flow of 1 to 3 i/min. Most times to

death, however, for this foam were in general agreement with the times of

death observed for other rigid polyurethane foam formulations, as shown in

Table 20. In some experiments the seizures continued for extended periods,

with as much as 50 minutes between onset and death. The authors did not

propose, however, that these convulsive seizures Indicated the presence of any

unusual toxicants.

-66-
4. SUMMARY

In this report a review has been made of the chemical nature and toxicity

of volatile products generated during the pyrolysis and combustion of rigid

polyurethane foams* A great number of gaseous products have been identified;

however, CO and HCN appear to be the predominant toxicants. The generation of

both CO and HCN was found to increase with increasing temperature. At 1000®C,

the highest yields observed were 26.5 mg/g for CO [ 6 ] and 73.3 mg/g for HCN

[13].

The toxicities of the combustion products of rigid polyurethane foams

were evaluated by various test methods using lethality and Incapacitation as

the biological endpoints* These results are summarized in Tables 28 and 29.

The LC5 Q values for 30 minute exposures for most of the foams studied by the

NBS and the University of Utah test methods (static systems) were greater than

34 mg/ A in the non-flaming mode and ranged from 10 to 17 mg/Z in the flaming

mode. The LC^q values measured using the University of Pittsburgh and DIN

test methods (dynamic systems) also fell within this range of values.

By comparison, the relative toxicity of different cellulosic and polymeric materials, including rigid and flexible polyurethane foams, evaluated by

Levin et al. using the NBS toxicity test method ranged from about 10 to

50 mg/4 [37,38]. The data examined in this report indicate that the combustion products from rigid pol3mrethane fall within the toxicological range of a

wide variety of other products. Comparison of the LC^q values for rigid

polyurethane with the corresponding values for Douglas fir and flexible polyurethane foam suggests that rigid polyurethane is two to three times more

-67 -
toxic in the flaming mode than in the non-flaming mode* This difference,

however, is less than an order of magnitude and is not considered toxicologically significant.

Toxicity studies on nitrogen-containing materials have shown that in many

cases HCN is one of the primary toxicants along with CO and CO2

. Experimental

studies on a rigid polyurethane (in the flaming mode) using the NBS test

method have shown that the concentrations of CO, HCN, and CO2 generated during

the 30 min LC^q mass loading contribute to the toxicity. These concentrations

were 1800 ppm, 140 ppm, and 12,900 ppm for CO, HCN and C02 » respectively

[37,38]. From individual pure gas experiments, 4600 ppm was the calculated

LC^q (30 min) for CO and 160 ppm was the LC^q (30 min) for HCN [41]. In

presence of 12,900 ppm CO2

, the LC^q (30 min) for CO is estimated to be

reduced to 3700 ppm [41]. The experimental studies with CO and HCN gas

mixtures have shown that the gases act in an additive manner such that if the

relationship:

[CO]

LC CO

,

50 (30 min)

[HCN]

LC,^ HCN,,^

50 (30 min)

> 1

the animals die, and if it is < 1 , the animals live.

By combining the CO and HCN concentrations generated at the LC5 Q of rigid

polyurethane with the LC^q (30 min) values for the mixture of HCN and CO one

finds the following result:

1800 ppm CO 140 ppm HCN

4600 ppm CO 160 ppm HCN

-68-
Slace the sum Is greater than 1, one can conclude that enough CO and HCN was

generated In the combustion atmosphere of flaming rigid polyurethane to

account for the deaths that occurred.

The EC5Q values as determined with hind-leg flexion behavioral avoidance

model for 30 minute exposures range mostly from 4 to 9 minutes in the flaming

mode and 4 to 30 minutes in the non-flaming mode (Table 29). Toxicity results

based on this model agree with the general conclusion based on the lethality

data that rigid polyurethane is about two times more toxic in the flaming mode

than in the non-flaming mode. The ^1^50 values for 10 minute exposures as

determined by the University of Pittsburgh test method are similar for all

rigid polyurethane foams tested, indicating that there is no difference of

practical importance between the foams (Table 29).

The toxicity data based on time response (T^ and T^) are very scattered

and do not allow comparison as different experimental conditions (temperature,

concentrations) were used by various workers. Times to incapacitation (as

observed by collapse with the University of San Francisco’s method) occur in

about half the time needed for death.

The studies on the rigid polyurethane foams reviewed here indicate that

the degree of toxicity observed was not a function of the specific foam

tested. Furthermore, except in the case when a reactive type phosphorus

containing fire retardant was added to a formulation containing propoxylated

trimethylol propane, the addition of the fire retardants does not appear to

change the toxicity of the combustion products. In the one exception, the

very toxic bicyclic phosphate was formed during nonflaming combustion

[32,66,80].

-69-
5.

ACKNOWLEDGMENTS

The authors gratefully acknowledge the help of Dr. Joseph V, Rutkowski

and Mr. Sanford Davis, Center for Fire Research, NBS, for many helpful discussions. The help of Ms. N. Jason, Ms. M. Diephaus, Ms. A. Durham, and

Ms. C.S. Bailey who performed the literature search and compiled the references is greatly appreciated. This study was supported in part by the

Consumer Product Safety Commission, Dr. Rita Orzel, project officer under NBS

contract no. 753-1386 (CPSC Task Order No.. 84-8).

6.

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13. Woolley, W.D. , Fardell, P.J., and Buckland, I.G. , The thermal

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toxicants on toxicity of pyrolysis gases from synthetic polymers.

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temperature conditions in testing cellular plastics and other

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Hollingsworth, Z.R. , The performance of rats on a rotarod during exposure

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Tox. 2=506-521 (1977).

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-75 -
77e O’Flaherty, E.J. and Thomas, W.C., The cardiotoxicity of hydrogen cyanide

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78. Thomas, W.C. and O'Flaherty, E.J., Cytochrome ^ oxidax activity in

tissues of rats exposed to polyurethane pyrolysis fumes. Tox. and Appl.

Pharm. ^;463-472 (1979).

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victims. J. Forensic Sci. 11:167-174 (1966).

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toxicity. J. Comb. Tox. 114-162 (1977).

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without cholinesterase inhibition. Science 182 :1135-1136 (1973).

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to polyurethane. Ann. Occup. Hyg. 19:269-273 (1976).

83. Wright, P.L. and Adams, C.H., Toxicity of combustion products from

burning polymers: development and evaluation of methods. Env. Health

Persp. _n:75-83 (1976).

-76-
Table 1

Thermal Degradation Products Produced

from Rigid Polyurethane Foam

Compound Atmosphere Reference

Acetaldehyde 1,0 6,14,47

Acetamide 0 26

Acetic acid 0 30

Acetone 1,0 6,14,26,30,42

Acetonitrile I 13,16

Acetylene 1,0 6,14,28

Acrolein 0 30

Acrylonitrile I 13,16

Alkene 1,0 10,25

Allene I 6,14

Ammonia 0 26,30

Aniline 1,0 6,14,30,35

Aniline hydrochloride 0 26

Benzene 1,0 6,13,14,15,26,30

Benzonitrile I 6,13,14,16

Benzoquinoline 0 35

Butadiene I 6,14,15

1- Butene I 6,14

1- Butene- 3 -yne I 6,14

Butyraldehyde 0 47

Carbazole 0 35

Carbon dioxide 1,0 4,6,10,21,28,29,

30,35

Carbon monoxide 1,0 4,6,8,14,18,20,21

24,25,26,28,29,31

37,38,42,43,45,51,53

55,56,57,58,59,60,61

62,63,67,73,74,75,

76,80

Carbon tetrachloride 0 26

Chlorine 1,0 10

Chlorobenzene 0 30

Chloroethane 1,0 15,30

Chloroethanol 0 30

Chloroethylene 0 30

Chloro isopropanol 0 30

Chloromethane 1,0 15,30

Chloropropylene

4,4' -Diamino dimethyl diphenylmethane

1,0 15,30

0 35

4,4' -Diamino diphenylmethane 0 15,30

4,4' -Diamino methyl diphenylmethane 0 35

4,4' -Diamino trimethyl diphenylmethane 0 35

Dichlorobenzene 0 26

Dichloroethane 1,0 15,28,30

77
Table 1 (Continued)

Compound Atmosphere Reference

Dichlorofluoromethane 0 30

Dihydropyran I 6,14

Dimethyl benzoquinoline 0 35

2,6-Dimethyl quinoline 0 35

Dimethyl toluidine 0 35

1,4-Dioxane 0 30

Diphenylamine 0 35

Dipropoxydiene-trimethylolpropane I 6,14

Dipropoxyene-trimethylolpropane I 6,14

Dipropoxy-one-trimethylolpropane I 6,14

Dipropoxy-trimethylolpropane I 6,14

Dipropropylene glycol methyl ether 0 35

Ethane 1,0 6,14,15,47

Ethanol 1,0 15,26,30

Ethylbenzene I 15

Ethylene 1,0 6,14,15,28

Ethylene oxide 0 44

4-Ethyl- l-phospha-2 , 6 , 7- tr ioxabicyclo [2.2.2]

octane- 1 -oxide

[bicyclic phosphate ester]

1,0 32,33,34

4 - EthyIquino1 ine 0 35

Formaldehyde 0 80

Formamide 0 47

FREON I 6,14

Hydrocarbons (C^) I 13

Hydrocarbons (C^^Hy) 0 29,30

Hydrogen bromide 0 31

Hydrogen chloride 0 20,26,28,29,30,75

Hydrogen cyanide 1,0 8,13,16,17,19,20,21,

25,26,29,30,31,37,38,

42,43,45,47,51,56,57,

58,60,61,62,63,75,

77,80

Hydrogen fluoride 0 31

Indazole 0 35

Indole 0 35

Isobutene I 15

Isopropropanol 0 30

Isoxazole 0 35

Methane 1,0 6,14,26,30,67,72,

73,74,75

Methanol 1,0 6,14,30

Methylacetylene I 6,14

3-Methyl benzoquinoline 0 35

2-Methyl-l- butene I 6,14

Methyl ethyl ketone 0 30

2-Methyl propenal I 6,14

78
Table 1 (Continued)

Compound Atmosphere Reference

Methylquinoline 0 35

Monoproproxy- t r imethylo Ipropane I 6,14

Naphthalene I 13

Nitric oxide 0 75

Nitrogen dioxide 0 75

Nitrogen oxides 0 25,26,28,31

3 , 8-Phenathroline 0 35

Phenol I 15

p-Phenylenediamine 0 30

N-phenyl P-toluidine 0 35

Polycyclic aromatics 0 35

Propane 1,0 13,28,47

n- Propanol 0 30

Propenitrile I 6,14

Propionaldehyde I 6,14

Propylene I.o 6,14,15,28,47

Propylene oxide 0 47

Pyridine I 13,16

Quinoline 0 35

Styrene I 6,14

Tetrapropoxydiene- tr imethylolpropane I 6,14

Tetrapropoxyene-trimethyloIpropane I 6,14

Tetrapropoxy-trimethylolpropane I 6,14

Toluene 1,0 6,13,14,15,26,30

2 , 4-Toluenediamine 0 30

Toluene monoisocyanate 0 47

Toluidine 0 30,35

Toluidine hydrochloride 0 26

N-tolyl butylurethane 0 35

Trichlorofluoromethane 1,0 4,6,14,15,26,28,

29,30

Trichloroethyl phosphate 1,0 10

Trimethyl benzoquinone 0 35

Tr imethyUndole 0 35

Trimethyltoluidine 0 35

Trimethylquinoline 0 35

Tripropoxydiene-trimethylolpropane I 6,14

Tripropoxyene-trimethylolpropane I 6,14

Tripropoxy-one-trimethylolpropane I 6,14

Tripropoxy-trimethylolpropane I 6,14

Tripropylene glycol methyl ether 0 35

Urea 1,0 10

Water 1,0 4,6,14,29

Xylene I 6,14,15

I - inert atmosphere

0 - oxidative atmosphere

79
Table 2

Products from Pyrolysis of a Sample of a Rigid Urethane Foam [6]

Product Concentration (yg)^

Compound 500 ®C 750''C 1000 “C

0.67 + 0.10

2 —

CO 0.29 + 0.11 2.77 + 1.07 26.45 + 10.0

CH,

4

0.02 + 0.02 0.66 + 0.34 15.31 + 6.4

CO^ 39.31 + 10.80 70.77 + 6.64 83.99 + 25.0

Ethene 0.02 + 0.01 0.49 + 0.16 11.40 + 5.31

Ethyne 1.40 + 0.67

Ethane 0.02 + 0.01 0.30 + 0.18 2.02 + 0.76

Propene 1.20 + 0.31 5.43 + 2.0 16.27 + 3.95

H^O 10.44 + 0.90 9.59 + 1.14 26.87 + 1.23

Propyne 0.02 1.10 + 0.46

Allene 2.25 + 1.50

Ethanal 0.21 + 0.08 1.85 + 0.70 9.07 + 1.63

1,3-Butadiene 1.11 + 0.44

l-Buten-3-yne 0.13 + 0.02

FREON 7.53 + 1.23 9.41 + 2.93 8.04 + 1.37

2-Me thy1-1-butene 0.08 1.27 + 0.65 3.57 + 0.38

Acetone (+propanal) 1.15 + 0.96 3.78 + 0.36 8.14 + 0.97

Propenitrile 0.32 + 0.22 2.78 + 1.68

2-Methyl propenal 1.75 + 0.19

Benzene 0.67 + 0.51 3.40 + 1.47 7.38 + 2.92

Toluene 0.22 + 0.03 1.28 + 0.59 3.73 + 2.06

Xylene 1.07 1.98 + 0.61

Styrene 1.22 + 1.05

Benzonitrile 7.73 + 3.15

Propoxylated trimethylol propanes

One mg samples of foam were pyrolyzed.

80
m

XI

ca H

CO

(U

)-l (U X

CL

cooEc

(UQOo

V4 z

cac

"O

(U

(0oaEoo

(U QuE

COo

fu

<uc

CO XX

(UX3

fHo

Pu-O

•H

C50 •H

PPEoXo3

•TaoX

cxcoX3XEouXo

•1—1, 32

CiC ooE X

iHXXX vO <J^ CO X • • • • c iH cs o^ O rH rH rH N3XXXcX tH 00 ON 3 • • • • X o ON <r CM oH

rH Cvj m o mX

in

<o

sf

C3

43

X

X o X s X X 00 00 ON 00 CO 43 N • • • • X CL c X X X X -O’ X X X o X 43 43 a XX X

So

CL

X •o o X X X X T3 o. X X o X X X

•H

m in in lO

X o c • . • • X X o cn CM •Cf X X 43 X E X

So

X

X

N ^ X X o « a X X X < X X X u A X E E X 43 X X o X o o X X X X X X X p X X X g -o X X X o X X X X o T3 X PO 00 00 o a o X c • • « » X X X X o CO X X X X o X X X X •H X X X M-i X z 43 ON CN tH 00 m X X z • • • • X X X CD u o m 00 o So So So z in cn in X X X M

(U X

cO XaXoX3-

So XXXoXoo o o y

to o o o

CL CL Q Q 2 2 XEX

c/2

C

M CJ

Q

81
Major

Nitrogen-Containing

Thermal

Products

from

Flexible

and

Rigid

Polyurethane

Foams

Decomposed

in

a

Nitrogen

Atmosphere

[16]

B

COo

u*

QJc

«u

<uu

3

tHo

eu

'3’ CM

rgo

enO

00

OJ

H

X

(U rH

Pb

«

CMd

>3‘ d

so

CO

T3

•H

00

•H

PC

82
Table 5

Temperature Dependent Yield of HCN from

Rigid Polyurethane Foams Decomposed in Inert Atmospheres

'oam Temp

(°C)

HCN Concentrations (mg/g)

500 600 700 800 900 1000 1200 Ref

A 5.1 8,6 31.5 50.9 13

B 5.1 6.4 47.1 73.2 13

C 1.5 6.5 18.6 38.1 13

D 1.5 3.1 7.6 50.8 13

4 1.1 11.1 36.0 16

SYSPUR 0.5 8.0 48.8 60.7 17

PAPI No. 3 0.23 19

TDI No. 8 0.45 19

83
Table 6

HCN Generation from Rigid Polyurethane Foams

Decomposed in Air at 500® C [19]

Foam

Fire

Retardant

Blowing

Agent

Nitrogen

in Foam

(%)

HCN

(mg/g)

PAPI Tr is (2-chloroethyl)

phosphate

CFCl^ 4.53 8.0

PAPI - CFCl^ 4.87 11.5

PAPI - CFCl^ 4.87 12.8

PAPI - CFCl^ 4.99 14.1

TDI - CFCl^ 5.09 0.5

TDI^

- CFCl^ 5.53 9.0

PAPI FYROL 6 CFCl^ 5.73 4.3

PAPI - CO^ 6.66 17.1

PAPI - CO

2 6.85 14.6

TDI - CO

2

7.05 0.5

^ Crude TDI

84
Table 7

Combustion Products from Rigid Polyurethane Foam

Under Flaming Conditions [20]

Foam

Blowing

Agent

Fire

Retarded

Maximum Gas

CO

(ppm)

Concentration

HCN

(ppm)

PAPI-ether CO

2 + 275 10

PAPI-ether Fluorocarbon + 700 32

PAPI-ester CO

2 - 2000 100

MDI-sucrose Fluorocarbon + 950 100

85
Table 8

Release Rate Data for Rigid Boardstock Polyurethane [24]

Maximum Generation Rates

G3.S (mg/min-m^) Time to Maximum

(sec)

NO 5070 13

X

HCN 1750 12

CO 45800 36

“2 805000 17

Total organics 18900 10

m = Meter

86
Table 9

Rigid Polyurethane Foam (GM 30) Toxicity Measurements

Using the NBS Toxicity Test Method [37, 38]

Furnace

Labor- temp.

Mode atory (®C)

LC^q (95% Confidence Limits)

30 minutes

(mg/Jl)

30 min + 14 days

(mg/iO

(95%

Confidence

50 Limits)

(mg/£)

Flaming NBS 570-575 14.3 (13.4-15.3) 13.3 (12.2-14.5) -

4 610-625 >38.4^ >38.4^ -

8 640 14.4 (11.7-17.8) 11.3 (7.6-16.8) 8.9 (5.1-15

Non- NBS 525-550 >39.6^ >39.6^ — Flaming 4 560-577 >33.9^ >34.0^ -

8 590 >35.1^ >35.1^ %29.3

440“C 4 440 >39.6^ >39.6^

8 440 >35.2^ >35.2^ >35.2^

^0% of the animals were affected.

One animal was affected.

87
Table 10

Atmospheric Gas Concentrations and Percent Carboxyhemoglobin

Calculated at the LC,._ (30 min) Values for GM 30 Decomposed

by the NBS Toxicity Test Method [37]

Combustion

Mode COHb CO HCN

(mg/i) (%) (ppm) (ppm)

Flaming 14.3 64 1800 140

Non-Flaming >40 >47 >1700 > 44

88
Table 11

Toxic Effects of the Combustion Products of Rigid

Polyurethane Foam Using the University of Utah Test Method [43]

Combustion

Mode Material FR EC

b

50

(mg/£)

LC

c 50

(mg/il)

Flaming CM 29 5.2 + 1.8 11.2 + 1.9

CM 31 + 6.7 + 1.2 14.2

GM 35 - 5.8 + 1.3 12.1 + 4.1

GM 37 - 3.9 + 1.0 10.9 + 1.5

GM 39 - 4.8 + 2.1 16.6

Non-Flaming GM 29 - 8.9 + 3.8 >40

GM 31 + 9.0 + 2.2 >40

GM 35 - 10.8 >36.7

GM 37 - 6.8 + 3.4 >36.7

GM 39 - 4.0 + 1.6 10.9 + 1.6

^Fire-retardant

.

^EC^q values + standard error calculated for loss of the leg-flexion

avoidance response during 30 minute exposure,

cLC^q values calculated on deaths occuring during the 30 minute

exposure and 14 days post-exposure period.

89
Table 12

Calculated CO and HCN Mean Concentrations Generated

at the Incapacitating and Lethal Smoke Concentrations Produced

During the Flaming Decomposition of Rigid Polyurethane Foam

in the University of Utah Studies [43]

EC^q (30 min) ^^50 min. + 14 days)

Material ~C0 HCN CO HCN

(ppm) (ppm) (ppm) (ppm)

GM 29 790 60 1690 130

GM 31 910 70 1930 140

GM 35 880 70 1340 145

GM 37 610 40 1710 110

GM 39 710 45 2460 150

90
Table 13

RD(-» Values Calculated for Different Rigid Polyurethane Foams

Decomposed by the University of Pittsburgh Test Method [49]

RD^q Values^

Sample

Fire

Retardant

(Zm

95%

Confidence Limits

(mg/2,)

GM 29 - 0.28 0.23 - 0.36

GM 31 + 0.21 0.11 - 0.39

GM 35 - 0.20 0.07 - 0.58

GM 37 - 0.23 0.11 - 0.49

RD^q values were based on a 10 minute exposure and 5 minute

recovery period.

91
Table 14

Sensory Irritation (RDcq), Stress Index (SI 100), Acute

Mortality (LC^q) Values, ana Asphyxiation Concentrations from Rigid

Polyurethane Foams Examined by the University of Pittsburgh

Test Procedure [45]

Samples RD

a

50

SI 100^ LC

c 50

Asphyxiation

Cone

.

(g) (mg/il*) (g) (mg/ £) (g) (mg/S,) (g) (mg/Jl)

GM 29 0.124 0.62 0.7 1.17 10.4 17.3 2-8 3.3-13.3

GM 31 (FR) 0.093 0.47 0.7 1.17 8.2 13.7 2-8 3.3-13.3

GM 35 0.092 0.46 0.9 1.50 7.5 12.5 2-7 3.3-11.7

GM 37 0.085 0.42 0.5 0.83 8.0 13.3 2-6 3.3-10.0

Concentration necessary to reduce respiration rate by 50% in a 10 minute exposure

and 5 minute recovery period.

^Concentration which produces a 50% decrease in the stress index (maximum is SI 200)

.

Concentration necessary to kill 50% of the test animals in a 30 minute exposure

and 10 minute recovery period.

* recalculated value by using the following formula

wt (g)

chamber air flowrate (Jl/min) x exposure time (min)

X 1000 mg/g

92
Table 15

Toxicity of the Pyrolysis Products of Rigid Urethane Foams Decomposed

on a Volume Basis^ or a Weight Basis'^ [51]

Sample

Volume

or weight

Fire

retardant Temp

(“O

Gas Cone.

CO

(ppm)

in Air

HCN

(ppm)

COHb

(%)

Number of

Deaths

Out of 20

1 V 600 1,100 60 34.2 0

2 V + 600 1,000 75 43.6 0

3 V + 550 1,500 100 45.2 0

600 1,800 150 55.0 2

1 w - 300 450 25 22.9 0

400 1,900 75 48.0 4

2 w + 350 1,000 50 36.1 0

400 2,200 100 59.8 11

3 w + 400 2,000 60 55.2 0

450 4,400 100 62.4 20

v: 300 X 10 X 5 mm

w: 1.2 g/100 mm

93
Toxicological

Effects

on

Rats

Exposed

to

Combustion

Products

from

Polyurethane

Foams

Evaluated

According

to

the

DIN

Toxicity

Test

Method

(53^

55] 1 u

CQ c U c cu o 00 o 3 CM o CM

C3‘^5 •-4 cn 4-1 (U '

(U 06 C*4 1 vO 1 C3^ 1 CM Q m in -O’ C XI

CO as S'? cu ou < C3^ <r 4 cn CM CM

*T3CU T3 4J

CO cn CU cu T3 4J

m o 00 00 00 00

cn cn CM CM -H

4J 4J

— '—

CO CO CD o 00 o in

>-> 1-H --4 . 0 0 z z X CM 00 o o o o CM OJ • • • • • • o -C3 CM o r>. IM cn u c m cn in 00 C31 MQ O o o o o o X E >o cn 00 o o o o CU Ou >o 'cr cn C3\ C'- o CD Qu — * * «k « c vO cn '0- 'O’ in C3^ M t—4

"O’ cn cn

a.

O o o o o o E CJ o o o o o o

cu 0 vO 00 in VO C'- £h

CU

u

JZ

cu 00O in 'O’ o o --4 E 00 • • • • • • CO cu w

m m m in in in

cn 3

CO4Jc

cu CO V4 T3

>-4 + 1 CS4 cO 4J

CU 06co

•r4 cu 4J

CO ~a

a c <T cu E 00 m CO -H cn cn

cu Q

00

O Pv

CM r>.m

CM

vO '3' 'O’ I 00 vOCM

00 CO 00 ^ CM

00 CJ* CM o o o 0^ O CM

CM CM \0 o o o o o o

00m 00

'O’ l>»

—4

CM CM \0 o o o o o o m vo T'. o o o o o o

cn

(U u3Co

(U c

o, o

>>

4J -U 00 4J c c

•H 0) JZ o m c

•H

O 3 O

CO 00 rH 0) c T3

(0 T3 -H 0)

0)> TJ

0)00

(0c

0)ou

0)aw

m

m

(0 lom

X

0)I

0)vO

cn cn

i-H fH

CTJ cO E e 0) vj

-iH »—4 4mJ

C

C (U c

CO (fl cn *H

CD (U o o c c

cn oj (1) cu ^ ;-i a) 0)

C|-| >4-4

X 0) cu 0) >-l c Q CO XI O t3 QJ

94

of

the

nominal

mean

value

before

exposure
Table 17

Toxicological Effects on Mice Exposed to Combustion

Products from Rigid Polyurethane Foam [58]

Incapacitation

Materials

Fire

Retardant

Time

Mean

(min)

S.D.^

(min)

^“^50

(min)

ip b

s (min)

Series 1^

RFA 5.77 0.47 5.75 2.60

RFB + 6.15 0.35 6.25 2.23

RFC + 7.52 0.50 7.50 1.69

Series 2^

RFA — 16.9 8.47 13.2 2.99

RFB + 19.7 6.06 17.0 2.16

Standard deviation of mean incapacitation time

j V

T^: Toxicity index = AW*t^

where V is the voltime of exposure chamber, t. is the incapacitation

time, and AW weight of material consumed.

' 2 'Surface area of specimen: 300 cm ; exposure chamber volume 125 1 .

Surface area of specimen: 450 cm^; exposure chamber volume 600 1 .

95
Table 18

Mean Time to Collapse After Exposure of Mice to the Thermal

Decomposition Products from a Rigid Polyurethane

Heated at 850°C [62]

Sample Weight

(g)

Maximum Gas

CO

(ppm)

Concentrations

HCN

(ppm)

Time to

Mean

(min)

Collapse

S.D.

(min)

0.50 700 52 3.80 0.35

0.74 800 48 2.58 0.39

0.91 800 68 2.26 0.21

1.15 700 105 2.20 0.47

1.45 800 122 1.69 0.18

1.75 600 124 1.56 0.18

S.D. Standard deviation of the mean of 5 exposed animals.

96
Table 19

Comparison of Toxicity Results from Fire Retarded vs Non-Fire Retarded Rigid Polyurethane Foams Decomposed

According to the University of San Fransisco

Toxicity Test Method [64]^

Fire

Material Retardant T.

X

(min)

"d

(min)

M

10

(%)

^^20

(%)

R1 - 9.64 + 2.31 14.10 + 0.74 0 100

R2 CBO^ 8.28 + 1.39 10.62 + 1.10 38 100

R3 FYROL 6 10.91 + 1.51 13.69 + 1.41 0 100

a = rising temperature mode (40*C/min from 200 to 800° C)

b = chlorinated butylene oxide-based polyol fire retardant

T^ = mean time to first sign of incapacitation + standard deviation of the

mean times from 2 tests

T, = mean time to death + standard deviation of the mean times from 2 tests

a —

M^q = mean mortality after 10 minutes from 2 tests

M^q = mean mortality after 20 minutes from 2 tests

97
Table 20

Toxicity Results for Rigid Polyurethane Foams Decomposed According

to the University of San Francisco Method Using Different

Temperature Modes [67, 69]

T, Mean CO Mean CH, d 4

(min) (ppm) (ppm)

Rising temperature program (40“C/min from 200 to 800 °C)

R1 10.64 + 0.85 23.92 + 2.14 4630 .3735

R2 8.56 + 1.57 23.74 + 2.11 4125 2660

R3 8.14 4" 2.45 25,69 + 0.80 4660 1765

R4 6.53 + 2.52 24.93 + 2.69 6215 2290

SI 12.62 + 1.24 15.14 + 0.62 - S2 12.12 + 0.16 17.29 + 0.96

Fixed temperature program (800 “C)

R1 4.00 + 1.44 8.70 + 0.35 2290 2960

R2 3.10 + 0.37 7.56 + 0.53 2375 2320

R3 3.04 + 0.46 9.43 + 0.55 2740 1760

R4 4.80 + 3.52 12.15 + 0.47 5935 2605

T. = Mean time to incapacitation as indicated by staggering + standard

deviation of the mean times for 4 tests for R2, 2 tests for all other foams.

T^ = Mean time to death + standard deviation of the mean times for 4 tests

for R2, 2 tests for all other foams.

Sample

Designation

T.

1

(min)

98
Table 21

Effect of Aging on Toxicity of Rigid Polyurethane Foams

as Determined According to the University of San Francisco Method^

Time to Death (min)

Sample Time of

Designation Testing 0 time 9 months 16 months 2 years

14.10^ 23.92®

10.62^ 23.74®

13.69*^ 25.69®

14.05^ 23.52^ 24.93®

a Rising temperature mode (40®C/min from 200 to 800“C)

b Reference 64

c Reference 65 (sample composition similar to R4)

d Reference 70

e Reference 67

99
Table 22

Char Yield and Toxicity of Pyrolysis Gases from Rigid

Polyurethane Foams as Determined According to the University of San Francisco

Toxicity Test Method [70]

Sample

Designation

Char Yield^

(%) (mxn)

Maximum CO

(ppm)

Rising temperature program (40"C/min from 200 to 800°C)

R4 12.6 24.93 7180

R3 15.9 25.69 6380

R1 19.6 23.92 5760

R2 28.6 23.74 5650

Fixed temperature program (800‘’C)

R3 10.2 9.43 3220

R4 10.9 12.15 8250

R1 12.2 8.70 2770

R2 16.8 7.56 3280

aChar yield at time of death of the last surviving animal.

100
Table 23

Comparison of Toxic Effects from a Rigid Polyurethane Foam Decomposed

at Either Fixed Temperatures

Temperature Program According

Toxicity

(300 to 800°C) or

to the University ' Test Method [72]

With a Rising

of San Francisco

Forced

Air

Flow

Temperature

Mode

Mean Time^ To

CO^

(ppm)

Staggering

(min)

Convulsions

(min)

Death

(min)

None Fixed 8040 19.15 22.85 25.12

Rising 2760 18.1 19.5 22.5

1 %!min Fixed 5600 7.78 9.63 12.93

Rising 720 5.7 8.0 10.1

CO concentration at the time of death of the last surviving animal or at the

end of 30-minute test.

^Average CO concentration and time to toxic effect was calculated by arithmetic

averaging the results from all the fixed temperatures (300 to 800°C) or those values obtained experimentally using the rising temperature program

(40°C/min from 200 to 800°C).

101
Table 24

Gas Generation and Time-to-Incapacitation Results Following

Exposure of Rats to the Combustion Products from Rigid Polyurethane

Foams Decomposed According to the University of Michigan

Test Procedure [75]

Mean Maximum Gas

c Cone

.

Average Gas Cone

.

d

Sample

Time to

Incap

.

S.D.^ CO CO^ GH,

4

HCN HCl Acrolein^ NO

(min) (min) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

A 39.5 2.95 1300 11500 20 9 30 0,06 0.1 1.3

C 28.5 4.47 1850 8000 15 28 51 0.20 0.2 1.8

D 28.2 1.47 2238 6675 8 44 123 0.44 0.1 1.4

^3.5 g sample.

^Standard deviation of all the times to incapacitation of four rats in two tests.

cHighest concentrations measured at 25 to

*^Average concentration over the length of

Acrolein and NO^ may not be accurate due

45 min.

run.

to possible color interferences

.

102
Table 25

Toxicological Effects Produced in Rats Following a 20-Minute Exposure to

CO, Smoke from the Combustion of Douglas Fir, Rigid Polyurethane

Foam, or a Fire-Retarded Rigid Polyurethane Foam [32]

Time to

Test

Material Cone. FR COHb

(%)

Move from

25-cm Circle

(sec)

Response

to Pain

(pinprick)

Other Comments

CO 1500 ppm - 38-53 12.4 Suppressed

Wood 5 g - 30-46 11.4 Normal Respiratory distress

Wood 18 g - 62 >60 None Extreme respiratory distress

All died within 24 hours

Foam ING 0% 28-33 6 Suppressed Normal behavior

Slight staining of nares

Foam ING 4% 23-26 ING One dead at end of exposure

Focal seizures at end of

exposure

Grand mal seizures in

43 to 70 minutes

No parasympathetic signs

Normal CO unloading

Foam ING 8% 5-6 >60 None All animals showed

myoclonic jerks which

progressed to status

epilepticus and death

No parasympathetic signs

FR = Fire retardant : 0, 0-diethyl-N,N-bis (2-hydroxyethyl) -aminomethyl phosphonate.

ING = Information not given.

I

103
Table 26

Summary of Behavioral Assessments of Rats Following 20 Minute

Exposures to Smoke From the Non-Flaming Combustion of Fire

Retarded Rigid Polyurethane Foams [66]

Time to Move

Sample FR From 25 cm Circle Additional Observations

1 (16%) Convulsions in chamber

8/8 dead at 18 minutes

2 VIRCOL (18%) Convulsions in chamber

4/8 dead on removal

2 were immobile and 2 were

still convulsing

7/8 dead at 6 minutes after

removal

8/8 dead at 15 minutes after

removal

3 none 1-4 sec. 8/8 active and normal

behavior

4 ANTIBLAZE 19 (10%) 1-4 sec. 8/8 active and normal

behavior

5 ANTIBLAZE 19 (15%) 1-4 sec. 8/8 active and normal

behavior

6 ANTIBLAZE 19 (30%) 2-8 sec. No convulsions or tremors

observed

3/8 active and normal

behavior

5/8 inactive-had difficulty

breathing. Expired 18-24

hours after test

7 ANTIBLAZE 19 (10%) 2-4 sec. 8/8 active and normal

behavior

FR: Fire retardant

a: foam known to produce the toxic bicyclic phosphate ester

b; FR = 0 ,0-diethyl-N,N-bis(2-hydroxyethyl)-aminomethyl phosphonate

104
Table 27

Acute Toxicity of Smoke from Trimethylol Propane-Based Rigid

Polyurethane Foams Containing Various Phosphorus Additives [79]

Total

Phosphorus

Content

(Wt. %)

Non-Flaming Flaming

Additive^

Specimen

Constimed

(g)

Rat'^

Mortality

Specimen

Consumed

(g)

„ c Rat

Mortality

None 0 2. 9-3.0 0/8 5.1 0/8

Brominated Phosphate 0.8 4.3 0/8 ND ND

Reactive Phosphonate 2.1 3.0 7/8 4. 8-5.0 0/8

Chlorinated Phosphonate 2.6 4.1 8/8 4. 8-5.

9

0/8-8/8

Chlorinated Phosphate 1.7 4.5 5/8 5.0 0/8

Polyammonium Phosphate 5.1 3.7 8/8 4. 9-8.0 0/8-1/8

Sample size was 8 x 8 x 2.5 cm weighing approximately 5g

^16% by weight

Number of rats that died/number of rats exposed for 20 minutes and observed

during a 14 days post-exposure period

Not determined

105
Table 28

Toxicological Effects Based on 30 Minute Exposures to Rigid Polyurethane

Foams Thermally Decomposed by Different Test Methods

LC^q Values

Combustion

Mode

Test

Method

Furnace

Temp.

(“O

Material

Designation 30 min

(mg/il)

30 min +

Post Exposure

(ms/ i)

Reference

F NBS 570-575 GM 30 14.3 13.3® 37,38

640 GM 30 14.4® 11.3^’® 37,38

610-625 GM 30 >38.4^ >38.4®*® 37,38

600 RPU^ —

11.0® 42

F UTAH 570 GM 30 11.2® 43

570 GM 31 /FR - 14.2® 43

600 GM 35 - 12.1® 43

580 GM 37 - 10.9® 43

700 GM 39 - 16.6® 43

NF/F PITT ramped GM 30 - 17.3® 44

20®C/min GM 31/FR 13.7® 44

GM 35 - 12.5® 44

- GM 37 “ 13.3® 44

NF DIN 400 PUR 1 29. 0<^ 52

500 PUR 1 7.5^^ - 52

600 PUR 1 6.6^i - 52

NF NBS 560-577 GM 30 >33.9® 34.0®’® 37,38

525-550 GM 30 >39.6 >39.6® 37,38

590 GM 30 >35.1® >35.1®’® 37,38

440 GM 30 _ >39.6®’® 37,38

440 GM 30 - >35.2®’® 37,38

NF UTAH 540 GM 30 _ >40® 43

560 GM 31/FR - >40® 43

550 GM 35 - >36.7® 43

530 GM 37 - >36.7® 43

630 GM 39 - 10.9® 43

F Flaming c : Post-exposure period 10 min.

NF Non- flaming d : Post-exposure period not noted

FR

a

b

Fire retardant

Post-exposure period 14 days

Sample from real fire

e : Study performed with NBS Toxicity Test

Method by non-NBS laboratory for ILE [38]

106
Incapacitation

Effects

from

Exposure

to

Rigid

Polyurethane

Foams

Decomposed

by

Different

Test

Methods

00

<ua

C

<u

<u

u-t0) oi

00CO

00CO

CO

CO CO CO CO CO <• -O'

0^ ON o^

<r -O’ <r 'O' M M

'O' <r 'O' <r

ST <r 'O' 'O'

f's CO

CO CO CO CO CO 'T 'T 'T 'T 'T

CO O

m

a

ds

C II

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00 o E

I I

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CM rs. v£) CM NO 'T 'T 'T

I I I I .... I I I I I I o o o o

om

o

u

c ^ •H oj e ^

00 O E

CO w

ON <r CM p" 00 (JN 00

• • • • • • • 00 00 m NO m CO 'T

COA

CO (3N O 00 00 O

ON 00 ON O NO 'T

CM iH

•H 01 a TJ

ca o

a. s

COa

C

oiPmPi

Pm

•H o o .H m t'' CJN o I—

1

uo rs o

P4

0) Ml

CO CO CO CO CO CO CO CO CO CO CO S s S S S S S S S S S

CO s

u O o O O O O O O o o

cdPm O >—I m ON

CO CO CO CO CO S S S S S

u o o o o

Pm

i-l S

PmK

Pm

iJS

Pm

hJ

T3

Ml O B H B CO JZ cn <: H c/3 <

(U Ml pa H M pa H H 0) s

z B Pm Z B

C

o

Ml

CD3

E

O

c^

(U TJOS

Pm

PmPmZ

Pm Pm Z Z

CO ^ 'J -O U. 2 U.

107

Amount

of

material

causing

50%

decrease

in

respiratory

rate/volume

Hind-leg

flexion

behavioral

avoidance

response
NBS-114A (REV. 2«*0) U.S. OEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 85/3224

2. Performing Organ. Report No.| 3. Publication Date December 1985

4.

TITLE AND SUBTITLE

A Review of the Literature on the Gaseous Products and Toxicity Generated from

the Pyrolysis and Combustion of Rigid Polyurethane Foams

5.

AUTHOR(S)

Maya Paabo and Barbara C. Levin

6.

PERFORMING ORGANIZATION (If Joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENTOF COMMERCE

Gaithersburg, MD 20899

7. Contract/Grant No.

I. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

U. S. Consumer Product Safety Commission

Bethesda, MD 20207

10.

SUPPLEMENTARY NOTES

I

I Document describes a computer program; SF-185. FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

The literature on rigid polyurethane foam has been reviewed with an emphasis on

the gaseoxis products generated under various thermal decomposition conditions

and the toxicity of those products. This review is limited to publications in

English through 1984. Carbon monoxide (CO) and hydrogen cyanide (HCN) were the

predominant toxicants foxind among more than 100 other gaseous products. The

generation of CO and HCN was found to increase with increasing combustion

temperatures. Many test methods were used to assess the acute inhalation

toxicity of combustion products from varioxis rigid polyurethane foams.

Lethality, incapacitation, physiological, and biochemical parameters were

employed as biological end points. In general, the combustion products

generated from rigid polyurethane foam in the flaming mode appear to be more

toxic than those produced in the non- flaming mode. The LC^q values for 30

minute exposures ranged from 10 to 17 mg/

I

in the flaming mode and were greater

than 34 mg/ 2. in the non-flaming mode. With the exception of one case in which

a reactive type phosphorus containing fire retardant was used, the addition of

fire retardants to rigid polyurethane foams does not appear to generate xinusual

toxic combustion products.

12.

KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Carbon monoxide; combustion products; fire retardants; hydrogen cyanide;

literature reviews; polyurethane foams; rigid foams; thermal decomposition;

toxicity

13.

availability

I xi Unlimited

I I For Official Distribution. Do Not Release to NTIS

I I Order From Suoerintendent of Documents, U.S. Government Printin* Office, Washington, D.C.

20402.

I y) Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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