Whether one or other of these mechanisms predominates, or their interrelationship, remains unclear. The polyurethanes used were elastomers based on TDI, which could potentially have differing decomposition mechanisms to their foam counterparts. 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. Do memory foam mattresses give off toxic fumes? Ann occup Hyg 19:269273, Levchik SV, Weil ED (2004) Thermal Decomposition, combustion and fire-retardancy of polyurethanes - a review of the recent literature. The authors also noted that the presence of aldehydes was detected during the flaming combustion of the flexible foam, albeit in extremely low yields. Polyurethane. Substituted ureas decompose between 235 and 250C and carbodiimides decompose between 250 and 280C. Equation 2 calculates the FED of the major asphyxiants, CO and HCN, but without taking oxygen depletion or CO2 driven hyperventilation into account. However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. The authors made this assertion based on the yield of average CO from post-flashover fires being 2009mgg1. It is likely that the fire toxicity of fire retarded polyurethane materials is largely dependent on the specific fire retardant present. The authors acknowledged that the lower nitrogen recovery fraction for the flexible foam could be due to fuel nitrogen being lost as isocyanates, which are known to escape into the effluent plume, while for rigid foams they are more likely to be trapped in the burning solid (Woolley & Fardell 1977). The relation of the FED to the material-LC50 is given in equation4. 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. 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. Further fragmentation of these molecules led to the production of HCN, acetonitrile, acrylonitrile and a range of olefinic fragments. These fires are large, relative to the enclosure, and produce greater volumes of effluent, affecting occupants over a much wider part of any building. However, during the combustion of polyurethane foams, the HCN yield is notably higher when the fire progresses from smouldering to flaming combustion. The trimerisation results in a highly stable isocyanurate ring which confer additional thermalstability to polyisocyanurates (Scheme7). The reaction of a urethane with another isocyanate will produce an allophanate (Scheme5). The authors noted that a large number of the data available relating to the test conditions were vague or completely undefined. As the availability of oxygen becomes lower in proportion to the amount of fuel, the yields of certain toxic gases will increase. Primarily, isocyanates react with alcohols to produce urethane linkages in the polymer (Scheme1). The difference in the decomposition of rigid and flexible polyurethane foams was investigated by Chun et al. 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. Ureas and urethanes decompose between 160 and 200C. p 102-120. These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. 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. 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. Humans may react differently than animals exposed to toxic materials. Burning foam will emit mainly carbon monoxide, carbon dioxide and small traces of other toxic gases, such . 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. 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. (PDF) The fire toxicity of polyurethane foams - ResearchGate I. Hietaniemi et al. Int Anesthesiol Clin 33:181, Kimmerle G (1976) Toxicity of Combustion Products with Particular Reference to Polyurethane. Hydrogen chloride (HCl) and hydrogen bromide (HBr) are strong acids which dissociate entirely in water. 2013). In others, under reduced oxygen concentrations, the fuel lifts from the surface, but ignition does not occur (Christy et al. 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. (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. The yields of CO and HCN at varying and temperature are presented in Table5. 3 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. In both rigid and flexible foams, aniline and p-aminotoluene were reported, which correlates with the work of Ravey and Pearce (1997) who reported that isocyanates that did not volatilise were converted into amines in the condensed phase. Babrauskas et al. Additionally, a polyol-rich residue is left behind that begins to fragment and volatilise between 300 and 600C. That smell comes from volatile organic compounds, or VOCs, chemicals used in the mattress manufacturing process. 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. What does polyurethane foam give off when burned? Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. The controlled atmosphere cone calorimeter. 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. Global usage is expected to expand from 13.65 Mt in 2010 to 17.95 Mt by 2016. 14) (UK Fire Statistics 2013). The dangerous concentrations of some important toxic fire gases are shown in Table4 alongside the influence of ventilation condition on their yields. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. This is unusual as this test method is usually well-ventilated and the results are not similar to reports of other authors (such as Levin et al. These isocyanate derived cross-links can include biurets and allophanates (Fig. When a liquid fuel gives off enough vapors so that it can be ignited and burn, has reached its? 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. The three compartments were connected by doors and the target room contained an open vent. TNO Report. The test method that produced toxic product yields associated with under-ventilated flaming was the NBS cup furnace toxicity method, which yielded 180210mgg1 of CO and 1620mgg1. 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. Springer Nature. 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. TDI is primarily used in the production of flexible foams, which are used in the furniture and interior industries. decomposition products will burn. These yields are comparable to that of the results reported by Blomqvist et al. 6 Sources of Toxic Chemicals (VOCs) in Your Home Based on the available literature, the non-flaming decomposition of both rigid and flexible polyurethane foams, in both air and nitrogen, can be generalised into a number of key steps (Fig. A large majority of the literature indicates that the addition of fire retardants does not increase toxicity of polyurethane foams. Additionally, the self-addition of isocyanates to produce isocyanurates (v in Fig. Polyurethane foam may be formed at a construction site or installed in the form of board stock (see the "Composite Insulations, Structural Insulated Panels" section). The first being a depolymerisation which would dissociate the polymer to isocyanates and alcohols, the second being dissociation to a primary amine, an olefin and carbon dioxide. When a one gram sample of foam was decomposed in air, CO was formed at a lower temperature than in nitrogen (300C vs 400C), with a relative concentration of 5000ppm at 500C. 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. When formed at the site, there is a potential for a completed-operations exposure. The overall toxicity of polyurethane materials followed a similar trend to their HCN yields; with flexible foams generally being the least toxic, rigid foams being slightly more toxic and polyisocyanurate foams being the most toxic. Experimental data reported a 28% recovery of DAT which supports the proposed decomposition mechanism. (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. Fire and Materials 11:p129, Paul KT, Hull TR, Lebek K, Stec AA (2008) Fire smoke toxicity: The effect of nitrogen oxides. CEN/TS 455452 (2009) Railway applications - Fire protection on railway vehicles Part 2: Requirements for fire behaviour of materials and components, Chambers J, Jiricny J, Reese CB (1981) The Thermal Decomposition of Polyurethanes and Polyisocyanurates. Is Polyurethane Foam Toxic, And Should You Avoid it? - The Safe Parent This value decreased to 18mgg1 at ~2.0.