1982), a developmental method (SwRI/NIST method) which used a radiant heater on the sample which lead into a 200 L exposure chamber, a cone calorimeter (ISO 5660 2002), a furniture calorimeter (as described in Babrauskas et al. As the main reactive group that isocyanates react with, polyols are a major component of the resulting polyurethane product. polyurethane foam production and up to a point the amount of water added will be inversely proportional to the density of the foam. Allergy 63:p583591, Pitts WM (1995) The global equivalence ratio concept and the formation mechanisms of carbon monoxide in enclosure fires. Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. These types of approaches have used existing rat lethality data, as described in ISO 13344 (1996) or more recently, based on the best available estimates of human toxicity thresholds as described in ISO 13571 (2007). By using this website, you agree to our The authors studied decomposition at 900C of foams, partly decomposed foams, smokes, and pure MDI to assess the hydrogen cyanide (HCN) content and noted that the yields of HCN were directly related to the nitrogen content. Aromatic diisocyanates, which are commonly used in the production of polyurethanes, have a slightly more complicated chemistry compared to monoiscyanates due to the electronic effects of two isocyanate groups. Substituted ureas decompose between 235 and 250C and carbodiimides decompose between 250 and 280C. At >800C these compounds further fragment into simple molecules (such as HCN, CO, CH4 and CH2O) and PAHs. PubMedGoogle Scholar. al, 2014). One analysis of fire victims' blood showed a trend of declining COHb and a rise in cyanide concentrations (Anderson et al. (1990) also reported increased HCN yields when the sample was allowed to smoulder before flaming in similar apparatus as above. (1981) on polycarbodiimides and polyureas enabled the determination of the source of the organonitriles and HCN during thermal decomposition. This is when flame retardant chemicals were added to the foam or coverings to stop the furniture from burning so ferociously. An FED equal to one indicates that the sum of concentrations of individual species will be lethal to 50% of the population over a 30min exposure. Similarly, the polyether based foam produced 15.1mgg1 to 28.1mgg1. 2005; Blomqvist & Lonnermark 2001). Fire gases contain a mixture of fully oxidised products, such as carbon dioxide (CO2), partially oxidised products, such as carbon monoxide (CO) and aldehydes, fuel and fuel degradation products, such as aliphatic or aromatic hydrocarbons, and other stable gas molecules, such as hydrogen halides (HCl, HBr) and hydrogen cyanide (HCN) (Kaplan et al. 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. Toxicology 115:7, Henneken H, Vogel M, Karst U (2007) Determination of airborne isocyanates. The data also does not specify the fire retardants used. This equation only relates to lethality, or cause of death. There are two reasons for this: The yields of the major toxic products (carbon monoxide (CO) and hydrogen cyanide (HCN)from N containing materials) will be much greater. The smoke density chamber (ISO 5659-2) showing a sampling probe for fire smoke toxicity. A summary of these results can be found in Table9. The authors also noted that the presence of aldehydes was detected during the flaming combustion of the flexible foam, albeit in extremely low yields. Substituted aromatics containing electron withdrawing groups further increase the reactivity of isocyanates by increasing the partial positive charge on the isocyanate carbon via a resonance withdrawing effect. Fire retardants, such as gas-phase free radical quenchers, have been reported to increase the yields of CO in well-ventilated conditions by preventing the oxidation of CO to CO2. 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). The non-flaming decomposition of non-fire retarded polyurethane foams in air is generally quite well understood and comparable to the inert atmosphere decomposition, in terms of both products and mechanisms. However, from a fire toxicity perspective it is generally assumed that heat and other gases will have already prevented survival, while other toxicants such as CO or HCN, will be present in lethal quantities further from the fire where the oxygen depletion would not be considered harmful. Polyether polyols are more resistant to hydrolysis, but less stable to oxidation, while for polyester polyols it is the opposite. There is some contradiction the literature as to the effect fire retardants have on the overall toxicity of polyurethane foams. Non-fatal UK fire injuries requiring hospital treatment, 1955-2013 (UK Fire Statistics 2013). A polyether polyol (i) and a polyester polyol (ii). This is due to the large range of available fire retardants found in polyurethane foams, which suggests that the toxicity will likely follow the general trends in the literature for all materials regarding fire retardants. Humans may react differently than animals exposed to toxic materials. Energy and Buildings 43:p498506, Stec AA, Hull TR (2014) Fire Toxicity Assessment: Comparison of Asphyxiant Yields from Laboratory and Large Scale Flaming Fires. The authors associated this with the effects of the Cu2O catalytically oxidising the HCN into N2, CO2, H2O and a small amount of nitrogen oxides. However, spray foam insulation is a highly energy-efficient product and quickly offsets its manufacturing footprint. 1982), and a three . In a 12-square-foot area, urethane was totally burned off, but the rest suffered more minor damage. 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). The test conditions were designed so that the fire conditions met the ISO 19706 (2007) fire type 2 (well-ventilated flaming fire <0.75) and fire type 3b (post-flashover fire in large or open compartments ~2.0). Preliminary calculations suggested that 27% of the TDI should be recovered as DAT. Taking this into consideration, the steady state tube furnace and the controlled atmosphere cone calorimeter both produced the highest yields of HCN in under-ventilated conditions. 12, feeds the sample (typically around 25g of pellets or granules) into its hot zone at a fixed rate, under a controlled air supply, inside a horizontal silica tube of diameter 48mm, allowing adequate mixing of fuel and oxidant. The transport industries have adopted the smoke density chamber (SDC) ISO 56592 (2012) and ASTM E662, for quantification of toxic product yields (Fire Test Procedure Code 2010; CEN/TS 455452 2009) using simple pass/fail chemical detection (e.g. Asphyxiant or narcotic gases cause a decrease in oxygen supplied to body tissue, resulting in central nervous system depression, with loss of consciousness and ultimately death. These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. Centre for Fire and Hazard Science, University of Central Lancashire, Preston, PR1 2HE, UK, Sean Thomas McKenna&Terence Richard Hull, You can also search for this author in National Bureau of Standards, Gaithersburg, MD, Levin BC, Paabo M, Birky MM (1983b) Interlaboratory evaluation of the 1980 version of the national bureau of standards test method for assessing the acute inhalation toxicity of combustion products, NBSIR 832678, National Bureau of Standards, Gaithersberg, MD, Levin BC, Paabo M, Fultz ML, Bailey CS (1985) Generation of Hydrogen Cyanide from Flexible Polyurethane Foam Decomposed under Different Combustion Conditions. I. Neviaser and Gann (2004) compiled the toxic potency data for a range of materials including a number of fire retarded and non-fire retarded polyurethane foams. When a liquid fuel gives off enough vapors so that it can be ignited and burn, has reached its? The difference with other polyurethane foams is that memory foam also contains added chemicals that increase its viscosity and elasticity, hence its alternate name, viscoelastic foam. At a CO concentration of 10 ppm, impairment of judgement and visual perception occur; exposure to 100 ppm causes dizziness, headache, and weariness; loss of consciousness occurs at 250 ppm; and 1000 ppm results in rapid death. 8-80, addressing . Fire Safety Science Proceedings of the ninth international symposium. However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. Apparatus where changes rapidly allow little time for sampling and measurement of mass loss and effluent compositionat a specific value of, with resultant errors and uncertainties. Ureas and urethanes decompose between 160 and 200C. Short chains with high functionality results in highly cross-linked polyurethane polymers which is characteristic of rigid foams. This step dramatically reduced fire deaths, which was considered a triumph at the time. Toxic product yields frommaterials involved in fires depend on a number of factors. 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. Research predicting the carbon monoxide evolution from flames of simple hydrocarbons, reviewed by Pitts (1995), has shown the importance of the equivalence ratio . This causes deterioration in mental and muscular performance. 1982), and a three-compartment large scale test. The Steady state tube furnace apparatus, ISO/TS 19700. Fire Research Notes 951:p117. 9). Most bench-scale methods have non-constant combustion conditions, such as those in closed chambers exposed to a constant source of heat, including the smoke density chamber (SDC) (ISO 56592 2012), and static tube furnace tests, such as the NF X 70100 (2006). To a lesser extent, parameters such as temperature and oxygen concentration also affect the yields of toxic products. Isocyanate structure also affects the reactivity of the isocyanate group. The relation of the FED to the material-LC50 is given in equation4. 1992), shown in Fig. However, in the field of combustion toxicity testing, this under-ventilated burning is the most difficult to create using bench-scale apparatus. The polyester based foam produced nearly double the amount of HCN between 900 and 1000C than the polyether foam with an increase from 20.8mgg1 to 38.0mgg1. (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. The polyester fabric produced 9293mgg1 of CO when burned with very little difference in the flaming or non-flaming conditions. Equation2 represents the generally accepted case that there are only two significant asphyxiant fire gases, CO and HCN. Despite their name, the term polyurethane is used to describe a family of polymers whose monomers are joined by a range of functional groups primarily derived from the polyaddition of polyisocyanates and polyalcohols. Damage was most severe to the exterior. Known as "solid gasoline" in the insurance industry, once a polyurethane fire starts, it usually results in a total loss of property and loss of life, according to Federated Insurance. NO. 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). However, while the char produced when the polymer was heated at 370C contained only 20% of the total nitrogen from the polymer, 40% of that (8% of the total nitrogen in the polymer) was recovered as HCN when the char was burned at 600C. In order to relate the fire effluent toxicity to a "maximum permissible loading", the FED can be related to the mass of material in a unit volume which would cause 50% lethality for a given fire condition. The sample is spread evenly in a silica boat over a length of 800mm and fed into a tube furnace at a typical rate of 1gmin-1 with flowing airat a rate of 2-10 L min-1. Most rigid foams and speciality polyurethanes use polymeric MDI derivatives which are mixtures components such as dimers and trimers (Fig. Carbodiimides are produced by the reaction of isocyanates in the presence of a catalyst (such as phospholine oxides) (Scheme8) (Avar et al. Correspondence to Interscience Publications, London, Purser DA (2008b) Chapter 2: SFPE Handbook of Fire Protection Engineering (Ed. City, Salt Lake, UK Fire Statistics 2013 (and preceding years) United Kingdom, Fire Test Procedure Code (2010) Maritime Safety Committee, (MSC 87/26/Add.3) Annex 34, Part 2 Smoke and Toxicity Test. Bott et al. While well-ventilated fire scenarios are routinely used for assessment of flammability, because the object is to stop the fire growing to the out of control stage, where fire toxicity is concerned, the important fire stages are under-ventilated. Nitrogen dioxide dissolves rapidly in water to form nitric and nitrous acid. As fires grow, they become ventilation controlled, and fires in enclosures such as buildings rapidly change from well-ventilated to under-ventilated. UPDATED 8/16/2011 The Massachusetts Division of Fire Safety (DFS) is investigating the causes of three house fires that were ignited while insulation contractors were installing spray polyurethane foam. (1972) noted that the yellow smoke was produced up to around 600C, where it would then decompose to give a family of low molecular weight, nitrogen containing products including hydrogen cyanide, acetonitrile, acrylonitrile, pyridine, and benzonitrile. However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. In a report from the same laboratory, Braun et al. The heating of polyurethanes in an inert-atmosphere results in the progressive rupturing of bonds as a function of temperature. The main toxic combustion products can be divided into two classes: asphyxiant gases, which prevent oxygen uptake by cells, with loss of consciousness and ultimately death; and irritant gases which cause immediate incapacitation, mainly by effects on the eyes and upper respiratory tract, and longer term damage deeper in the lung. The half-scale ISO 9705 experiments showed a wider range of ventilation conditions up to ~2.0. However, due to the poor reproducibility of smoke chamber experiments, the tendency for it to give very low HCN yields, and the fact that the experiment is well-ventilated, the reported toxicity is likely much lower than in a real fire situation. National Fire Protection Association, Quincy, MA, pp 5482, Guo X, Wanga L, Zhanga L, Lia S, Hao J (2014) Nitrogenous emissions from the catalytic pyrolysis of waste rigid polyurethane foam. This char can decompose further, leaving behind a residue at >800C, to produce simple organic fragments and some polycyclic aromatic hydrocarbons (PAHs). Top of Page. It is therefore essential to the assessment of toxic hazard from fire that each fire stage can be adequately replicated, and preferably the individual fire stages treated separately. The lowest temperature at which a liquid will give off vapors at a sufficient rate to support a momentary flame across its surface is known as its: . Their development continued commercially in Germany, eventually leading to a global multibillion dollar industry (Vilar 2002). An equation has been developed for the estimation of the FED for lethality from the chemical composition of the environment in the physical fire(such as the bench-scale methods described in the following section) model taken from ISO 13344 (1996) and uses gas-LC50 values for lethality to provide referencetoxicity data for the individual gases to calculate toxic potency, based on rats exposed for 30min. However, a non-standard modification of the apparatus has been described, enclosing the fire model in a controlled ventilation chamber, in an attempt to replicate oxygen-depleted conditions. 1982), a developmental method (SwRI/NIST method) which used a radiant heater on the sample which lead into a 200L exposure chamber, a cone calorimeter (ISO 5660 2002), a furniture calorimeter (as described in Babrauskas et al. HCN also causes rapid incapacitation, preventing escape, and then, with CO, contributes to death from asphyxiation. The revised protocol is based on continuous sampling of the fire effluent. Once the material ignited, the yield of HCN increased to 3.8mgg1. At sufficiently high concentrations, or when attached to submicron particles, such as soot, most irritants can penetrate deeper into the lungs, causing pulmonary irritation effects which may cause post-exposure respiratory distress and death, generally occurring from a few hours to several days after exposure, due to pulmonary oedema (flooding of the lungs) (ISO 13571 2007). (2011) developed a mechanism based on both condensed and gas-phase decomposition in air. The chemical additives to the polyurethane are said to give off a distinct chemical odor that lessens after adequate ventilation. Anderson RC, Croce PA, Feeley FG, Sakura JD (1983) Study to assess the feasibility of incorporating combustion toxicity requirements into building materials and furnishing codes of New York State: Final report, vol I, II, III, Arthur D. Little, Inc. Report, Reference 88712, May 1983. These polyols will fragment and volatilise as the temperature increases, leaving behind a char (>600C). The difference in the decomposition of rigid and flexible polyurethane foams was investigated by Chun et al. Reaction between an isocyanate and an alcohol to produce a urethane, Reaction of an isocyanate with water to produce a carbamic acid which decomposes to produce an amine and carbon dioxide, Reaction of an isocyanate with an amine to produce a urea, Reaction of an isocyanate with a urea to produce a biuret linkage, Reaction of a urethane with an isocyanate to produce an allophanate linkage. Polymer International 53:p15851610. HCN analysis was performed using infrared (IR) spectroscopy using a short path-length gas cell, which is a questionable method for the quantification of HCN due to its poor IR absorption, high potential for interferences and a poor limit of detection. The non-flaming decomposition of polyurethanes in air or nitrogen can be summarised effectively usinga generalised mechanism based on the available literature (Fig. Equation 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. Additionally, the self-addition of isocyanates to produce isocyanurates (v in Fig. Both authors read and approved the manuscript. (2007). This makes the isocyanate functional group highly reactive towards nucleophiles with an available hydrogen. . Fire and Materials 31:p327354, Schnipper L, Smith-Hansen ES (1995) Reduced combustion efficiency of chlorinated compounds, resulting in higher yields of carbon monoxide. Only the SSTF has a heated reaction zone which replicates the hot layer. While the link between CO yield and equivalence ratio is well established, the yield of HCN in ventilation limited conditions shows more complicated behaviour for polyurethanes. Thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) showed that the polyether based polyurethane began to decompose at 258C, with a second decomposition stage at 350C (which could be attributed to the fragmentation of the polyether polyol). CO yields are generally very low for well-ventilated conditions (in the absence of halogens) but increase considerably under-ventilated combustion conditions. National Bureau of Standards, Washington D.C. Levin BC, Paabo M, Fultz ML, Bailey C, Yin W, Harris SE (1983a) Acute inhalation toxicological evaluation of combustion products from fire-retarded and non-fire retarded flexible polyurethane foam and polyester. Unfortunately, your body heat appears . FED model from ISO 13571, Equation The reaction of an isocyanate functional group with water (Scheme2) results in the formation of an unstable carbamic acid group, which in turn decomposes to release an amine and carbon dioxide.