Fire and Materials 31:p495521, Bott B, Firth JG, Jones TA (1969) Evolution of toxic gases from heated plastics. In the gas phase, isocyanates, amines and yellow smoke will begin to decompose at >600C into low molecular weight nitrogen containing fragments (such as benzonitrile, aniline and hydrogen cyanide (HCN)). Furniture, upholstery and curtains The controlled atmosphere cone calorimeter. 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. These reactions make up the basis of polyurethane chemistry and can be used to tailor polyurethanes with a range of properties by varying the structure and ratios of the individual components. 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. However, once one of the groups forms a urethane or urea, the activating effect on the other isocyanate is reduced, as ureas and urethanes are weaker activating groups than isocyanates. The samples were heated at 800C in a static tube furnace, with the effluent being cooled to <50C before entering an exposure unit. 1992), shown in Fig. 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. (1981) reported similar data by analysing the inert-atmosphere pyrolysis of a series of biscarbamates to act as model compounds representing polyurethane foams. 9). This suggests that the nitrogen in the char will more readily form HCN, even when the flaming is well-ventilated. It can be used for testing samples 100100mm and up to 50mm thick, in both the horizontal and vertical orientation. This prompted the authors to perform further studies in order to understand why allowing the foam to smoulder increased the yield of HCN during flaming combustion. Around 1015% of the nitrogen in the polymer can be converted into HCN with some being released in isocyanates, aminoisocyanates and amines in the fire effluent. Global usage is expected to expand from 13.65 Mt in 2010 to 17.95 Mt by 2016. This is true of ALL polyurethane foam since it is an organic material, just like wood or cotton fabric. The relationship between equivalence ratio and yields of CO and other products has been studied in detail for a wide range of materialsduring flaming combustion using two small-scale apparatus designed specifically for this purposethe ASTM E2058 fire propagation apparatus (Tewarson 2002) and the ISO/TS 19700 tube furnace apparatus (ISO/TS 19700 2013), in conjunction with a series of large-scale experiments used for validation (Gottuk & Lattimer 2002; Blomqvist & Lonnermark 2001; Purser & Purser 2008a). Biuret and allophanate bonds will decompose first between 100 and 125C. The relation of the FED to the material-LC50 is given in equation4. Smouldering was forced by an electrically heated resistance wire embedded in the sample and a load cell measured the mass of the sample throughout the experiment. The mechanisms of decomposition are well understood and the decomposition products of both rigid and flexible polyurethane foams are very similar at high temperatures. The authors proposed that once formed, these compounds could partially polymerise with volatilised TDI in the vapour phase to produce Woolleys yellow smoke. (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam. Preliminary calculations suggested that 27% of the TDI should be recovered as DAT. (2015) questioned their methodology and noted that the authors did not address the release of HCl and its contribution to the acute fire toxicity of the fire retarded foam. The three compartments were connected by doors and the target room contained an open vent. Is Polyurethane Foam Toxic, And Should You Avoid it? - The Safe Parent Therefore the contribution of HCN to fire deaths is difficult to assess, and analysis for CN is limited to cases where lethal concentrations of CO are absent. (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. (2007) assessed the toxic product yields of a flexible polyurethane foam that was designed for use in hospital mattresses. In the chamber, 0.23g of black char and 0.04g of yellow oil were recovered. 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 most widely used fire-test apparatus, stipulated in smoke regulations in most countries of the developed world, is the smoke density chamber as described inISO 56592 2012, andshownschematically in Fig. Several authors have investigated the relationship between bench-scale test data and large-scale test data using polyurethane foams. (1991a) compared a number of test methods. From this, the library of data was sorted into categories of combustion/pyrolysis conditions, material/product, type of test animal and toxicological endpoint. 13) (UK Fire Statistics 2013). 1984a). This is when flame retardant chemicals were added to the foam or coverings to stop the furniture from burning so ferociously. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. Fire and Materials 19:p6164, Shufen L, Zhi J, Kaijun Y, Shuqin Y, Chow WK (2006) Studies on the Thermal Behavior of Polyurethanes. 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. 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 Med Sci Law 21:60. This equation only relates to lethality, or cause of death. (1972). Isocyanate structure also affects the reactivity of the isocyanate group. decomposition products will burn. When formed at the site, there is a potential for a completed-operations exposure. Only the SSTF has a heated reaction zone which replicates the hot layer. At 650C, the yield of HCN from the CMHR-PUF increased up to ~2.0 where it reached a peak of 14mg of HCN per gram of polymer burned. Is Memory Foam Toxic? | Sleep Foundation 2013). NO. Additionally, a polyol-rich residue is left behind that begins to fragment and volatilise between 300 and 600C. In a 12-square-foot area, urethane was totally burned off, but the rest suffered more minor damage. Both authors read and approved the manuscript. Once sensitisation has occurred, even extremely low concentrations of airborne isocyanates can trigger fatal asthma attacks (Henneken et al. Do memory foam mattresses give off toxic fumes? The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. The non-flaming decomposition of polyurethanes in air or nitrogen can be summarised effectively usinga generalised mechanism based on the available literature (Fig. (1969) reported the decomposition of rigid polyurethane foams in both nitrogen and air to assess the production of CO, HCN and NH3. Equation Although these temperatures can provide a good general idea of which bonds will be likely to break down with heating, the steric and electronic effects of the attached groups can affect the strength of the bonds and thus the temperature at which the bond will decompose. 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. (PDF) The fire toxicity of polyurethane foams - ResearchGate The sample is a 7575mm square solid sheet and the standard for smoke measurement states that the results are only valid at the thickness tested (typically 14mm). As polyurethane foams have very low thermal inertia, application of heat or a small flame can be enough to ignite them. Is Your Mattress Releasing Toxins While You Sleep? - WebMD These yields are comparable to that of the results reported by Blomqvist et al. Isocyanates should be considered when assessing the fire toxicity of polyurethane foams, due to their acute irritating effects and chronic effects associated with exposure. The rigid polyurethane foam yielded ~55mgg1 CO and ~0.5mgg1 of HCN. 3 However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. Fire and Polymers II: Materials and Tests for Hazard Prevention 599:p498517, Chun BH, Li X, Im EJ, Lee KH, Kim SH (2007) Comparison of Pyrolysis Kinetics between Rigid and Flexible Polyurethanes. Woolley WD, Wadley AI, Field P (1972) Studies of the thermal decomposition of flexible polyurethane foams in air. The resulting substituted urea can then react with another isocyanate to produce a biuret linkage (Scheme4). The specific mass of the polyurethane sample was not provided by the author and the ventilation conditions were not clear as a result of this. Taking into consideration the issues with repeatability of large-scale testing, the authors asserted that the similar trend in HCN yields supported the good relationship between the tube-furnace and large-scale results. (1981) on polycarbodiimides and polyureas enabled the determination of the source of the organonitriles and HCN during thermal decomposition. p 1-30. By using infrared analysis, the authors were able to detect a range of compounds at each step, as summarised in Fig. Building renovations, demolition, or building disassembly done years later can disturb spray foam insulation. The protocol has been modified as a toxicity test by the mass transport industries, in the aircraft (EN 2826 2011), maritime (Fire Test Procedure Code 2010), and railway tests (CEN/TS 455452 2009). Each method is described briefly in the following section. (1972) suggested that the decomposition was initiated by the release of a nitrogen-rich material at 200300C which in turn decomposes into low molecular weight nitrogenous fragments above 500C. When polyurethane foam insulation burns it gives off toxic gasses, very high temperatures and large amounts of thick, black smoke. LC50 values should be referenced to the fire condition under which they were measured. Stec and Hull (2011) presented material-LC50 data for rigid polyurethane foam and polyisocyanurate foam, calculated using rat lethality data from ISO 13344 (1996). The formation of HCN was at a higher temperature in both air and nitrogen (400C and 550C respectively) with an average concentration of 200ppm at 500C. 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. 1986). In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanide. Fire Technology 40:p117199, NFPA 269 (2012) Standard test method for developing toxic potency data for use in fire hazard modelling, NFX 70 1001:2006 Fire Tests - Analysis Of Gaseous Effluents - Part 1: Methods For Analysing Gases Stemming From Thermal Degradation, NIOSH (1989) A summaryof health hazard evaluations: Isocyanates, 1989 to 2002, Paabo M, Levin BC (1987) A review of the literature on the gaseous products and toxicity generated from the pyrolysis and combustion of rigid polyurethane foams. However, when the TDI was unable to enter the pyrolysis zone, the slower, irreversible decomposition to diaminotoluene (DAT) would occur. VOCs have the ability to vaporize, or off-gas, at room temperature. Isocyanates were primarily produced during the first stage, and in the second stage primarily carbonyls (R2-C=O) and hydrocarbons were detected using infrared analysis. Under well-ventilated flaming (<0.8), the yields of CO2 and NO2 were at their highest, while the yields of CO and HCN were at their lowest. https://doi.org/10.1186/s40038-016-0012-3, DOI: https://doi.org/10.1186/s40038-016-0012-3. During polymerisation, isocyanates undergo a number of distinct reactions. Overall, the report provides access to a large pool of data organised into a material-LC50 and also helps demonstrate that the large majority of data available is for well-ventilated tests. Ureas and urethanes decompose between 160 and 200C. While it is evident that the HCN yield increases as a fire becomes more under-ventilated, the link between the nitrogen content of the fuel and the yield of HCN is less clear. 1982), the authors exposed male Fisher 344 rats in a 200L exposure chamber to the fire effluent from the flaming and non-flaming combustion of both materials. Some fire models, such as the cone calorimeter, fire propagation apparatus and smoke density chamber use the temperature of the radiant heater to preselect the radiant heat flux, and then check this using a radiant heat flux meter. Fire Safety Journal 7:p11, Kavanagh BP, Pearl RG (1995) Inhaled nitric oxide in anesthesia and critical care medicine. When polyurethane foam is burned, it gives off a wide variety of potentially harmful substances. CO yields are generally very low for well-ventilated conditions (in the absence of halogens) but increase considerably under-ventilated combustion conditions. Damage was most severe to the exterior. Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. 2008) and is 40kWm2 in the centre of the furnace at 650C and 78kWm2 at 825C. Toxic product yield data from the smoke density chamber (ISO 56592 2012), the controlled atmosphere cone calorimeter (based on ISO 56601 2002), the fire propagation apparatus (FPA) (ASTM E 2058), the French railway test (NFX) (NF X 70100 2006), and the steady state tube furnace (SSTF) (ISO/TS 19700 2013) were compared to published large-scale enclosure fire data (from a standard ISO 9705 room) for two polymers, polypropylene (PP) and polyamide 6.6 (PA 6.6). Most rigid foams and speciality polyurethanes use polymeric MDI derivatives which are mixtures components such as dimers and trimers (Fig. 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. Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. (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. When a liquid fuel gives off enough vapors so that it can be . The test room was 2.43.03.0m with a door (dimensions not specified) and a 1 to 2kg slab of foam in the centre of the room. Fire Res 1:p1121. Google Scholar, Allan D, Daly J, Liggat JJ (2013) Thermal volatilisation analysis of TDI-based flexible polyurethane foam. Toxicology 47:165170, Kaplan HL, Grand AF, Hartzell GE (1984a) Toxicity and the smoke problem. More recent work by Shufen et al. 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 the UK, the rapid rise in fire deaths, in particular those from smoke toxicity, between the late 1950s and the early 1980s has been attributed to the rapid growth in low cost polyurethane foam furniture, with superior comfort and lower cost than the natural fillings that preceded it. statement and Polyether polyols are more resistant to hydrolysis, but less stable to oxidation, while for polyester polyols it is the opposite. Fire and Materials 16:p3743, Barbrauskas V, Harris RH, Gann RG, Levin BC, Lee BT, Peakcock RD, Paabo M, Twilley W, Yoklavich MF, Clark HM (1988) Fire hazard comparison of fire-retarded and non-fire-retarded products, Special Publication 749. The half-scale ISO 9705 experiments showed a wider range of ventilation conditions up to ~2.0. It is likely that the fire toxicity of fire retarded polyurethane materials is largely dependent on the specific fire retardant present. 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 authors noted that a large number of the data available relating to the test conditions were vague or completely undefined. Busker RW, Hammer AH, Kuijpers WC, Poot CAJ, Bergers WWA, Bruijnzeel, PLB (1999) Toxicity testing of combustion products of polyurethane and polyvinylchloride. The standard specifies four test conditions, but fails to link them to particular fire scenarios. 2012). At this temperature around one third of the compounds mass was lost as volatile products, and the regenerated alcohol products were mainly present in the residue of the sample. Research predicting the carbon monoxide evolution from flames of simple hydrocarbons, reviewed by Pitts (1995), has shown the importance of the equivalence ratio . Free of VOCs and HAPs. Nitrogen dioxide dissolves rapidly in water to form nitric and nitrous acid. The authors noted that the yields of the toxicantsproduced an atmosphere in the tests which fell well below their Immediately Dangerous to Life and Health (IDLH) values. At high concentrations these acids can cause pulmonary oedema and death (Paul et al. As the global usage of polyurethane foams is expected to continue to increase yearly, it is important that the fire community have a clear understanding of the fire toxicity of polyurethane foams and the reasons why they produce significant amounts of toxic gases during combustion. The strain of two electronegative atoms (N and O) results in electron density being pulled away from the carbon atom, giving it a strong partial positive charge. OSHA Hazard Information Bulletins Fire Hazard of Polyurethane and Other NBSIR 822604. 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. Memory foam is a type of polyurethane foam. 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. The toxic product yields may be quantified from the gas concentrations and mass feed rate during the steady state burn period. Data from large scale fires in enclosures, such as a room, shows much higher levels of thetwo of the major toxicants, carbon monoxide (CO) and hydrogen cyanide (HCN) under conditions of developed flaming (Andersson et al. Anal Bioanal Chem 387:p219236, Herrington R, Hock K (1998) Flexible Polyurethane Foams, 2nd edn. The main asphyxiants, carbon monoxide and hydrogen cyanide have been widely studied and are the best understood (ISO 13571 2007). 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. Investigations by Woolley et al. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. But many products or materials continue off-gassing even after the "new smell" has gone awaythe fumes are just much more subtle. Spray foam can potentially generate toxic emissions under these circumstances. In a real fire, involving cycles of growth and decay of flaming combustion, the resulting yields of HCN from the combustion of polyurethane foams are likely to be higher than predicted in some bench-scale methods as a result of this two-step decomposition mechanism. Interscience Publications, London, Purser DA (2008b) Chapter 2: SFPE Handbook of Fire Protection Engineering (Ed. Results from these burn tests are used for comparison with the model developed to simulate flame spread, heat fluxes, and smoke development over time (Figure 1). McKenna, S.T., Hull, T.R. P.J. The Model Equations2 and 3 have been taken from ISO 13571 (2007). In a series of investigations, Purser and Purser (2008a) examined the yields of HCN from a range of materials and the conversion of fuel nitrogen to HCN. The second results in a brief stimulation, followed by severe depression, of respiratory frequency, also starving the body of oxygen, and causing convulsions, respiratory arrest and death (Alarie 2002). 2 (Avar et al. 50 Almost all unwanted fires are diffusion flames, with inefficient mixing of fuel and oxygen(as opposed to the "premixed" flames found in burner/combustion systems). 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. Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. The peak HCN value reached was 10mg per g1 in the under-ventilated tests. combustion modified high resilience polyurethane foam, Alarie Y (2002) Toxicity of Fire Smoke. Full-scale fires simultaneously involve different fire stages in different places, which are changing with time. Equation3 uses a similar principle to equation1 to estimate the combined effect of all irritant gases. The author acknowledged that there is a range of contradictory results available in the literature regarding their fire toxicity. However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. Acrolein and formaldehyde are formed especially from cellulosic materials under non-flaming decomposition conditions, but products of vitiated combustion contain other organic irritants. The fire toxicity of a material can also be expressed as a material-LC50, which in this case is the specimen mass M of a burning polymeric material which would yield an FED equal to one within a volume of 1m3. Self-addition reaction of two isocyanates to produce a uretidione, Self-addition reaction of three isocyanates to produce a isocyanurate ring, Reaction of two isocyanates to produce a carbodiimide. During flaming combustion of polyurethane foams, the yield of toxicants can be directly related to the fuel/air ratio, expressed as an equivalence ratio (). The calculations showed that, for both the rigid polyurethane and the polyisocyanurate, hydrogen cyanide is the major toxicant in smouldering, well-ventilated and under-ventilated flaming. Equation2 represents the generally accepted case that there are only two significant asphyxiant fire gases, CO and HCN.

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