A review of the literature on the gaseous products and toxicity generated from the pyrolysis and combustion of rigid polyurethane foams

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 a hundred 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,,, values for 30-min exposures ranged from 10 to 17 mg 1-in the flaming mode and were greater then 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.

The fire toxicity of polyurethane foams

“…4 2,4-TDI (i) and 2,6-TDI (ii) secondary decomposition mechanism where isocyanates trapped in the condensed phase are converted irreversibly into their amine derivatives. A review by Paabo and Levin (1987) found that there is no difference in the decomposition products of rigid and flexible polyurethane foams at high temperatures regardless of their differing degradation mechanisms at lower temperatures. Both types of foam yielded very similar products at temperatures above 600°C.…”

“…Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. However, as noted by Paabo and Levin (1987), many studies into the decomposition of polyurethane foams do not differentiate between flaming and non-flaming decomposition, and focus on the temperature of decomposition rather than the presence of flames. Therefore, in certain conditions, polyurethanes foams can reach their auto-ignition temperature and ignite which will significantly alter the effect the decomposition mechanisms and resulting products.…”

“…The formation of the toxicant in question was the result of an unusual reaction of the polyol in the foam, trimethylol propane, with the phosphate fire retardant in the gas phase. Paabo and Levin (1987) reviewed the literature of the toxic product generated by the combustion of rigid polyurethane foams. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams.…”

Pollutant emissions during the pyrolysis and combustion of flexible polyurethane foam

“…The 276 production of both compounds increased with temperature as a consequence of the thermal 277 degradation of heavier compounds (Paabo and Levin, 1987).…”

Evaluating the Impact of Fires on the Environment

“…Initially many studies were qualitative and investigated which organic species could be expected in fire gases as most previous experience of the characterisation of combustion gases was from controlled combustion rather than fires, e.g. the groundbreaking work of Levin et al at NIST [5][6][7][8][9][10]. It was not until the 1990s that large volumes of quantitative data concerning fire gas characterisation were first published to a great degree, such as that produced by SP [11][12][13].…”