Privacy The NFX generates data intermediate between the well-ventilated and under-ventilated fire conditions. 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. This steric hindrance can be offset by increasing the temperature of the reaction or by performing the reaction in the presence of a catalyst (Vilar 2002). Sensory and upper respiratory tract irritation stimulates the trigeminal and vagus nerve receptors in the eyes, nose, throat and upper respiratory tract causing discomfort, then severe pain. The peak HCN value reached was 10mg per g1 in the under-ventilated tests. 1999). This was enough to cause deaths both during and post-exposure. The authors noted no significant difference in the range of yields of isocyanates detected in either well- or under-ventilated conditions with a range of 1.0-1.6mgg1. It is inexpensive and easy to install, however, it is a severe fire risk and requires a thermal barrier to make it safe. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme5). This amine may then undergo further reaction with other isocyanates present to produce a urea (Scheme3). STM would like to acknowledge the University of Central Lancashire for provision of a studentship. The significant increased yields at 1000C and 1200C could also be attributed to pyrolysis of the nitrogenous combustion products into HCN due to the low air flow rate. During these tests, the PIR was set up as wall panels covered on two faces with aluminium foil. Using polyurethane indoors can expose you to fumes with a number of potential side effects. Farrar DG, Galster WA (1980) Biological end-points for the assessment of the toxicity of products of combustion of material. It is usually used in isomeric mixtures of varying ratios, with 80:20 2,4 to 2,6 being the most commonly used (Fig. The PIR at 1.75 resulted in 15% of the fuel nitrogen being recovered as HCN. 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. Urethane Foam Health Effects | livestrong Busker RW, Hammer AH, Kuijpers WC, Poot CAJ, Bergers WWA, Bruijnzeel, PLB (1999) Toxicity testing of combustion products of polyurethane and polyvinylchloride. 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. Bott et al. Fire and Materials 23:p171185, Hull TR, Paul KT (2007) Bench-scale assessment of combustion toxicity-A critical analysis of current protocols. 9). Once sensitisation has occurred, even extremely low concentrations of airborne isocyanates can trigger fatal asthma attacks (Henneken et al. (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. Full-scale fires simultaneously involve different fire stages in different places, which are changing with time. I. 2023 BioMed Central Ltd unless otherwise stated. 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. In a report from the same laboratory, Braun et al. It has been suggested that the reproducibility problems arise from the single point measurement (the tip of the probe may be in the centre of the plume, below it, or if mixing is more efficient, the upper layer may be recirculated through the flame), or the timing of the effluent sampling may cause instabilities (for example an initial proposal to sample after 8min was replaced by a proposal to sample when the smoke density reached its maximum). While the data presented is a useful compilation of toxic potency data from the available literature before 2004, the report does not take into consideration the conclusions of individual authors, the exact specifics of the test condition, and the validity of the results. 1981), probably because of increased use of nitrogen-containing synthetic polymers. 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. Rigid foam decomposed between 200 and 410C, while flexible foam decomposed between 150 to 500C. Both types of foam yielded very similar products at temperatures above 600C. The mechanisms of decomposition are well understood and the decomposition products of both rigid and flexible polyurethane foams are very similar at high temperatures. 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. (such as polyurethane foam) burn slower (have a lower (HRR) than higher-density materials (cotton padding) of similar makeup. Most polyurethanes are cross-linked to some degree and decompose without melting. The dangerous concentrations of some important toxic fire gases are shown in Table4 alongside the influence of ventilation condition on their yields. Additionally, the self-addition of isocyanates to produce isocyanurates (v in Fig. Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. depends on the mass loss rate of the specimen and the available air; for most methods one or both are unknown; will be increased by an unknown factor if products are recirculated into the flame zone. Over this period there was a corresponding shift from the main cause of death in fires being attributed to burns to being attributed to inhalation of smoke and toxic gases. However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. (1985) when a flexible polyurethane foam was first heated at a temperature below its auto-ignition temperature, followed by flaming combustion of the remaining char and residue at a higher temperature. 3) (Aneja 2002). The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. It forces combustion by driving the sample into a furnace of increasing heat flux at a fixed rate, so that, by running several tests with the same material with different ventilation conditions, each fire stage can be replicated by steady state burning. 1982), and a three-compartment large scale test. The dimerisation of two isocyanates is a reversible reaction that produces uretidione ring (Scheme6). 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. In the chamber, 0.23g of black char and 0.04g of yellow oil were recovered. 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. CO and HCN are the main asphyxiants produced during the combustion of polyurethanes and there have been a large number of studies published regarding their yields. The fire toxicity of polyurethane foams. When polyurethane foam insulation burns it gives off toxic gasses, very high temperatures and large amounts of thick, black smoke. Unlike carbon monoxide which remains primarily in the blood (as COHb), the cyanide ion is distributed throughout the extra-cellular fluid of tissues and organs (ISO 13571 2007). When the black char was burned at 600C, it yielded 14.95mg of HCN (65mg per gram of char) and the yellow oil yielded 21mg per gram of oil. It can continue to irritate people sensitive to chemicals or odors . In China and Japan, there are specific restrictions on the use of materials with high fire toxicity in high risk applications such as tall buildings, while an increasing number of jurisdictions permit the alternative performance based design approaches to fire safety. In a 12-square-foot area, urethane was totally burned off, but the rest suffered more minor damage. Non-fatal UK fire injuries requiring hospital treatment, 1955-2013 (UK Fire Statistics 2013). 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. Thermal decomposition of polyurethanes is usually the reverse of polymerisation, resulting in the formation their precursor functional compoundsdiisocyanates, diamines and dihydroxy compounds. National Fire Protection Association, Quincy MA, USA, pp 296, Purser DA, Purser JA (2008a) HCN yields and fate of fuel nitrogen for materials under different combustion conditions in the ISO 19700 tube furnace. 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. Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. 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. International Association for Fire Safety Science, Ravey M, Pearce EM (1997) Flexible Polyurethane foam. Unfortunately, your body heat appears . Elemental analysis of the polymer and the char showed that 80% of the nitrogen in the polymer was lost when heated at 370C, but only 0.6% was recovered as HCN when burned at 600C. (1972). This range of functional groups and their ratios in the polymer are a large contributing factor to the wide range of properties that polyurethane materials can possess. However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. PubMedGoogle Scholar. They attributed the different decomposition mechanisms to the physical form of the polyurethane foam, rather than to any chemical differences. 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). Terence Richard Hull. However, no amines were detected in the vapour phase. Polymer-Plastics Technology and Engineering 45:p95108, Singh H, Jain AK (2009) Ignition, Combustion, Toxicity, and Fire Retardancy of Polyurethane Foams: A Comprehensive Review. Substituted ureas decompose between 235 and 250C and carbodiimides decompose between 250 and 280C. The process of . The effects range from tears and reflex blinking of the eyes, pain in the nose, throat and chest, breath-holding, coughing, excessive secretionof mucus, to bronchoconstriction and laryngeal spasms (Purser 2008b). Other fire retardants such as melamine are reported to significantly increase the HCN yield of polyurethane foams. In the large scale test room, the sample smouldered for 1.5 to 2h, resulting in a HCN yield of 1.03mgg1. The authors noted that the polyester polyols were more stable than the polyether polyols, with the latter fragmenting at a lower temperature (300400C). In this case, the main reason for including isocyanate reactivity data is to explain the reactivity of isocyanates that are released into fire effluent during combustion. Fire and Materials 9:p125134, Levin BC, Paabo M, Bailey CS, Harris SE (1986) Toxicity of the combustion products from a flexible polyurethane foam and a polyester fabric evaluated separately and together by the NBS Toxicity Test Method. Higher temperatures resulted in the volatilisation of most of the polyurethane precursors via the formation of lower molecular weight compounds. In particular, the ventilation condition has a . J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. (1991a) compared a number of test methods. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. Rigid polyurethanes primarily produced aromatic compounds in the condensed phase products of decomposition, whereas flexible polyurethanes produced aromatics, alcohols, aldehydes and heterocycles. Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. Fire and Materials 31:p495521, Bott B, Firth JG, Jones TA (1969) Evolution of toxic gases from heated plastics. 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 reaction of a urethane with another isocyanate will produce an allophanate (Scheme 5). (2011) Aerospace series - Burning behaviour of non-metallic materials under the influence of radiating heat and flames - Determination of gas components in the smoke; ABD 0031 Fire-Smoke-Toxicity (FST) Test Specification (Airbus Industries); Boeing BSS 7239, Test method for toxic gas generation by materials on combustion. Ann occup Hyg 19:269273, Levchik SV, Weil ED (2004) Thermal Decomposition, combustion and fire-retardancy of polyurethanes - a review of the recent literature. Polymer Degradation and Stability 93:p20582065, Tewarson A (2002) SFPE Handbook of Fire Protection Engineering, 3rd ed. Polyurethane. 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). Recent work by Allan et al. Biuret and allophanate bonds will decompose first between 100 and 125C. 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. However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. The average combined yield of isocyanates recovered was 0.869mgg1 and the average yield of amines and aminoisocyanates was 0.321mgg1. Polyol fragments in the gas phase will also begin to decompose at >800C to produce simple organic fragments and PAHs. 10. 2012). 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. 3 The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. To a lesser extent, parameters such as temperature and oxygen concentration also affect the yields of toxic products. However, when the TDI was unable to enter the pyrolysis zone, the slower, irreversible decomposition to diaminotoluene (DAT) would occur. 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. Andersson B, Markert F, Holmstedt G (2005) Combustion products generated by hetero-organic fuels on four different fire test scales. In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanide. As a result of this, studies that use ventilation controlled conditions, such as those using the steady state tube furnace (ISO/TS 19700 2013), are more likely to give a realistic representation of these reduced oxygen environment fire conditions. Most fire deaths and injuries actually occur in residential fires, although assessment of fire toxicity is currently focused on areas where escape is restricted, such as aeroplanes, railway carriages, and passenger ships, which include requirements to quantify the fire toxicity of internal components. Equation Provided by the Springer Nature SharedIt content-sharing initiative. 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. Bulky substituents that impinge on the isocyanate group can reduce its reactivity. VOCs and Other Toxic Chemicals in Mattresses: What to Know Since then, Blais and Carpenter (2015) investigated a flexible polyurethane foam with and without a chloro phosphate (tris-dichloro-propyl phosphate TDCPP) fire retardant using a smoke box (ISO 56592 2012) to assess the toxicity. The overall toxicity of the combined materials was higher, and the average concentrations of the gases throughout the tests were consistently higher than that of the individual materials in both flaming and non-flaming conditions. Med Sci Law 21:60. 2), also results in cross-linking in the polymer. The authors noted that the total concentrations of CO and HCN during flaming combustion were greater than the sum of those from the individual materials. DiNenno) Fourth Edition. 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. 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. Fire Safety Journal 43:243251, Piiril PL, Meuronen A, Majuri ML, Luukkonen R, Mntyl T, Wolff HJ (2008) Inflammation and functional outcome in diisocyanate-induced asthma after cessation of exposure. Allergy 63:p583591, Pitts WM (1995) The global equivalence ratio concept and the formation mechanisms of carbon monoxide in enclosure fires. Material composition, temperature and oxygen concentration are normally the most important. While there were some problems, the data does show that the yields of toxicants from the polyurethane foam were generally most representative of post-flashover conditions in the test methods that were designed for ventilation controlled conditions, such as the steady state tube furnace and the controlled atmosphere cone calorimeter. The foam could be cleaned and a coating or metal cladding could be installed over it. 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. 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.
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