Most fuel nitrogen is released as N2, but in well-ventilated combustion conditions a proportion is released as oxides of nitrogen (mainly NO) and in under-ventilated combustion conditions a proportion is released as HCN (Purser & Purser 2008a). Technology, Gaithersburg MD, Babrauskas V, Levin BC, Gann R, Paabo M, Harris RH, Peacock RD, Yusa S (1991b) Toxic potency measurement for fire hazard analysis, special publication 827, National Institute of Standards and Technology. Additionally, HCN yields in both flaming and non-flaming conditions increases with temperature. The resulting substituted urea can then react with another isocyanate to pro-duce a biuret linkage (Scheme 4). FED model from ISO 13571, Equation 2011). The fire department was not immediately called, so the oil burned completely. Terence Richard Hull. Polyurethane foam when burned gives off - wiehoch.com While the smoke chamber experiment is known to give low HCN yields, and both scenarios are well-ventilated, the yield of HCN was almost 4 times as high during flaming combustion if the sample was allowed to smoulder first. Hazwoper lesson 3 Toxicology Flashcards | Quizlet Each of the decomposition steps took place at a lower temperature in air than in nitrogen, which further suggests the direct interaction of oxygen with the foam during decomposition. However, it does suggest that yield of toxic products is effected by covering the foam with another material during flaming combustion. When polyurethane foam is burned, it gives off a wide variety of potentially harmful substances. The production of HCN and other low molecular weight nitrogenous compounds from the high temperature decomposition of polyurethanes has been reported in the literature in recent years. This agrees with the fact that oxidation of NH3 and HCN to NO (and NO2, although it was not analysed in these experiments) would occur more readily during well-ventilated burning. At 300C, free isocyanates and alcohols were produced from the decomposition of these biscarbamates. The isocyanate precursors used in the production of polyurethane foams usually consist of aromatic diisocyanates such as toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI). The first step is the decomposition of the urethane bonds to release and volatilise isocyanates up to 300C, with long chain alcohols being left behind in the condensed phase, followed by the alcohols degrading at around 400C. Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. Progressive changes in the composition of a static specimen (for example due to char formation) provide additional complexity. The authors compiled toxicological data from a range of primary online databases and also requests were made to collect unpublished data that were not publically available. Woolley WD, Fardell PJ, Buckland IG (1975) The Thermal Decomposition Products of Rigid Polyurethane. As polyurethane foams have very low thermal inertia, application of heat or a small flame can be enough to ignite them. This was enough to cause deaths both during and post-exposure. 4)). The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. For any larger fire there will always be a significant yield of CO, HCN (from nitrogen containing materials), hydrocarbons and smoke. 95% of the demand for polyurethanes is situated in North America, Asian-pacific, and European markets; with demand expected to increase in Eastern Europe and South America in the next 1015 years. The polyester based polyurethane began to decompose at 284C with a secondary decomposition step at 359C. Is Your Mattress Releasing Toxins While You Sleep? - WebMD While several authors work has focused primarily on the nitrogenous products of decomposition, other publications have focused on the production of other compounds such as carbon monoxide. The widespread use of flexible polyurethane foams in furniture and other upholstery, where they are usually covered in some kind of fabric has prompted some authors to investigate the effects of covering the foam on the yield of toxic products. The flexible foam produced ~175mgg1 of CO and 5mgg1 of HCN. However, as the fire condition became under-ventilated (>1.5), the yields of both CO and HCN increased for both rigid polyurethane and the polyisocyanurate, while the yields of CO2 and NO2 decreased. Studies have found that infant mattressesespecially those made with polyurethane foam, which contains the hydrocarbon tolueneare a major off-gassing culprit (Boor, et. Whether one or other of these mechanisms predominates, or their interrelationship, remains unclear. The results indicated that the formation of the precursor, TDI, was much faster and preferable to depolymerisation when the volatile compounds could escape. al, 2014). Chem Co., Dow, Hertzberg T, Blomqvist P, Dalene M, Skarping G (2003) Particles and Isocyanates from Fires. Is Memory Foam Toxic? | Sleep Foundation However, bench-scale methods which allow the combustion conditions to change during the test are much more difficult to relate to full-scale fires, because the duration of each condition is unknown, and the behaviour of fires changes on scale-up. The effect of asphyxiants and deep lung irritants depend on the accumulated doses, i.e. It is difficult to draw more general conclusion from this work because the fuel-to-air ratio was not quantified, and the degree of mixing of fresh air and fire effluent, in the exposure chamber, is unknown. Over short periods, inhaled CO impairs an individuals ability to escape, causing different effects at different concentrations. FIRE INVESTIGATOR REVIEWS Flashcards & Practice Test | Quizlet Stec and Hull (2011) presented material-LC50 data for rigid polyurethane foam and polyisocyanurate foam, calculated using rat lethality data from ISO 13344 (1996). Fire Safety Science Proceedings of the ninth international symposium. (1999) tested both rigid and flexible polyurethane foams using a bespoke smoke chamber apparatus to assess the toxicity of the flaming combustion products of the materials to rats. Those with constant combustion conditions are more suited to producing data suitable for comparison and modelling: the steady state tube furnace (SSTF) (ISO/TS 19700 2013) has been specifically designed to achieve this. The severity of the effects increases with dose (Hartzell 1993). In some bench-scale apparatus the heat flux is constant, and often insufficient to sustain flaming at such low oxygen concentrations; further, an unknown quantity of fresh air bypasses the fire plume, so the ventilation condition, and hence, remains undefined. Additionally, the authors suggested the positions on the polyol chain where bond scission could occur, explaining the presence of the short-chain alkenes, aldehydes and ketones (Scheme9). Fire and Materials 31:p495521, Bott B, Firth JG, Jones TA (1969) Evolution of toxic gases from heated plastics. HCN yields reported in under-ventilated conditions vary depending on the composition of the material; with flexible foams producing less than rigid foams and polyisocyanurates producing the most overall. Over 90% of all industrial polyurethanes are based on either TDI or MDI (Avar et al. Global usage is expected to expand from 13.65 Mt in 2010 to 17.95 Mt by 2016. Based on the temperature of the test, the yields of HCN are extremely low when compared with the CO yields. Gaithersberg, MD, Babrauskas V, Twilley WH, Janssens M, Yusa S (1992) Cone calorimeter for controlled-atmosphere studies. Diesel engines use the principle of _____ to ignite fuel vapor. Fire and Materials 5(4):p133141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The yields of CO and HCN at varying and temperature are presented in Table5. 1995). As polyols are prepolymers, their molecular mass is relevant to their application, with flexible foams being derived from 1000 to 6000 daltons and few hydroxyl groups, while those used in rigid foams have short chains from 250 to 1000 daltons with high functionality (312 hydroxyl groups per chain). Both types of foam yielded very similar products at temperatures above 600C. One analysis of fire victims' blood showed a trend of declining COHb and a rise in cyanide concentrations (Anderson et al. The presence of Cu2O drastically decreased the yield of HCN in polyurethane foams at lower temperatures, but had little effect at high temperatures. This suggests that the nitrogen in the char will more readily form HCN, even when the flaming is well-ventilated. Further fragmentation of these molecules led to the production of HCN, acetonitrile, acrylonitrile and a range of olefinic fragments. The dangerous concentrations of some important toxic fire gases are shown in Table4 alongside the influence of ventilation condition on their yields. This suggests that any amines formed would have reacted with isocyanates in the vapour phase to form ureas, some of which would have condensed to produce the observed waxy white substance. However there was significant scattering of the results with both high and low outliers (26mgg1 at 1.22 and 9mgg1 at 1.95). Fire Hazards of Insulation Materials | American Family Insurance 2013). The first is by combination with the ferric ion in mitochondrial cytochrome oxidase, preventing electron transport in the cytochrome system and inhibiting the use of oxygen by the cells. Foam: Fire Hazard and Fire Barrier | Monolithic.org According to Tim Rodrique, the director of the DFS, investigators suspect that the fires were caused by the exothermic reaction that results from the mixing of the two chemicals used to make . In general, isocyanate (R-NCO) exposure causes irritation to the skin, mucous membranes, eyes and respiratory tract (NIOSH 1989). Potential Chemical Exposures From Spray Polyurethane Foam J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. Additionally, the authors reported a yield of 1315mgg1 of CO, 1.41.5mgg1 of HCN, and 1012mgg1 of NO. The yields of acid gases and nitrogen-containing products depend upon the proportion of the appropriate elements in the materials burned and the efficiency of conversion. The FED value is calculated using the exposed dose relationship (concentration-time product, Ct) for CO. They attributed the different decomposition mechanisms to the physical form of the polyurethane foam, rather than to any chemical differences. 2023 BioMed Central Ltd unless otherwise stated. The toxic hazards associated with fire and the inability of victims to escape from fire atmospheres may be considered in terms of major hazard factors: heat, smoke and toxic combustion products (Hartzell 1993). . Comparing the toxic potencies of different materials, the lower the material-LC50 (the smaller the amount of materials necessary to reach the toxic potency) the more toxic the material is. The polyisocyanurate, on the other hand, produced slightly more HCN than the rigid foam (17mgg1 vs 12mgg1). Isocyanate structure also affects the reactivity of the isocyanate group. Combustion Science and Technology 183(7):p627644, Saunders JH (1959) the Reactions of Isocyanates and Isocyanate Derivatives at Elevated Temperatures. The increased yield of HCN for the CMHR-FPUR between 650C and 850C is likely due to the increased fragmentation of nitrogenous organic compounds in the flame, similar to the behaviour during non-flaming combustion in air reported by Woolley et al. Using a cup furnace with a 200L sampling chamber (identical in design to the one used in the smoke chamber experiments), a 3.88g sample of foam was heated to just below its ignition temperature (370C) which yielded <1mgg1 HCN. The uptake, distribution, metabolism and excretion of cyanide is much more complex than for CO and quantifying CN- in fire victims is more expensive and not routinely undertaken. Carbon monoxide binds to the haemoglobin in red blood cells resulting in the formation of carboxyhaemoglobin (COHb), with stability 200 times greater than that of oxyhaemoglobin, impeding the transport of oxygen from the lungs to the cells in the body. Bench-scale methods used for generation of toxic fire effluentsideally should be capable of reproducing individual fire stages or combustion conditions, for input into models of combustion toxicity. ISO 56592 (2012) Plastics - Smoke generation - Part 2: Determination of optical density by a single-chamber test, ISO 56601 (2002) Fire tests Reaction to fire Part 1: Rate of heat release from building products (cone calorimeter method), ISO 9705 (1993) Fire tests Full-scale room tests for surface products, Kaplan HL (1987b) Effects of irritant gases on avoidance/escape performance and respiratory response of the baboon. The reported yields were extremely low for both CO and HCN, as the NBS smoke chamber apparatus is a well-ventilated fire scenario reported to give low HCN yields (Table6). In particular, reports that used non-standard tube furnace apparatus lacked sufficient information about the conditions of the experiment and as such were not included. The results from the SSTF and FPA show the best agreement with those from the full and 1/3 scale ISO room for both materials under a range of fire conditions. During flaming combustion of polyurethane foams, the yield of toxicants can be directly related to the fuel/air ratio, expressed as an equivalence ratio ().