The FED value is calculated using the exposed dose relationship (concentration-time product, Ct) for CO. 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. This shows that the reactions of isocyanates are much faster with amines and slower with carboxylic acids, urethanes and amides than for the alcohols used in polyurethane production. 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). Purser model, [AGI] is the concentration of inorganicacid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2]0.05. to FED. (2007). 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). The peak HCN value reached was 10mg per g1 in the under-ventilated tests. 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. 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. Furniture, upholstery and curtains ISO 19706 (2011) Guidelines for assessing the fire threat to people. 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). The resulting substituted urea can then react with another isocyanate to pro-duce a biuret linkage (Scheme 4). 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. At lower temperatures, decomposition differs, depending on the composition and physical properties of the polymer, although clear trends can be identified. Draeger tubes), conventional or Fourier transform infrared spectroscopy (FTIR) gas analysis, despite significant problems of reproducibility. MDI is a diaromatic diisocyanate compound that boils at 208C and is primarily used in the production of rigid foams. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. decomposition products will burn. The Steady state tube furnace apparatus, ISO/TS 19700. Top of Page. Overall, the results suggested that the polyether based polyurethane was less thermally stable in the presence of oxygen than the polyester, and both were generally less stable in air than in a nitrogen atmosphere. This causes deterioration in mental and muscular performance. As the main reactive group that isocyanates react with, polyols are a major component of the resulting polyurethane product. Each method is described briefly in the following section. In a 12-square-foot area, urethane was totally burned off, but the rest suffered more minor damage. (2007) suggests that their yields are not heavily dependent on the ventilation conditions and that the yields would likely only increase by a small amount during under-ventilated flaming. Voorhees suggested that the compound was a bicyclic phosphate compound and noted grand mal seizures followed by death in rats with a loading as low as 4% by weight of the fire retardant. 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. This can be explained by the fragmentation of nitrogen containing organics in the flame and in the effluent, as suggested bystudies of the inert-atmosphere decomposition of polyurethane materials. The average combined yield of isocyanates recovered was 0.869mgg1 and the average yield of amines and aminoisocyanates was 0.321mgg1. . 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. 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. Damage was most severe to the exterior. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme5). At 300C, free isocyanates and alcohols were produced from the decomposition of these biscarbamates. The revised protocol is based on continuous sampling of the fire effluent. True. Fire Safety Journal 40:439465, Aneja A (2002) Chapter 2, Structureproperty Relationships of Flexible Polyurethane Foams, PhD. It is usually used in isomeric mixtures of varying ratios, with 80:20 2,4 to 2,6 being the most commonly used (Fig. CO also combines with myoglobin in the muscle cells, impairing diffusion of oxygen to cardiac and skeletal muscles (Purser 2008b). Fire Res 1:p1121. For the purpose of estimating toxicity in fires, fire growth has been classified into a number of stages (ISO 19706 2011): Although on some occasions smouldering (oxidative pyrolysis) can generate toxicologically significant quantities of effluent (for example smouldering cotton, or polyurethane foam), typicallythe rate of reaction, and hence the amount of toxic species generated will be small, so it is unlikely to affect anyone outside the immediate vicinity. 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. Equations2 and 3 have been taken from ISO 13571 (2007). 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). In a compartment fire, the reactions of under-ventilated flaming occur in both the flame zone and in the hot upper layer. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. https://doi.org/10.1186/s40038-016-0012-3, DOI: https://doi.org/10.1186/s40038-016-0012-3. 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. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. 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. However, the yield of CO was lower in both the non-flaming and flaming combustion. Isocyanate structure also affects the reactivity of the isocyanate group. Similarly, Busker et al. (1999) used the controlled atmosphere cone calorimeter, but argues correctly,in the authors' opinion,that an instantaneous effective global equivalence ratio The initial decomposition of the foam, at >300C, results in the volatilisation of isocyanates, amines and Woolleys yellow smoke, leaving behind polyols in the condensed phase. For a fixed chamber volume (0.51m3), assuming complete combustion, the sample thickness will dictate the ventilation condition, thus a thin sample will burn under well-ventilated conditions with minimum toxic products, while a thicker sample might be expected to produce a high yield of CO and other products of incomplete combustion. A summary of these structures is shown in Fig. This results in relativelyhigh yields of CO and HCN during under-ventilated flaming and relatively low yields during well-ventilated flaming. 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. The difficulty of replicating the conditions of fully developed under-ventilated flaming on a bench-scale is caused by several practical problems. That smell comes from volatile organic compounds, or VOCs, chemicals used in the mattress manufacturing process. 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. 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. p 1-30. A "combustion modified high resilience" flexible polyurethane foam (CMHR-PUF) and a polyisocyanurate (PIR) foam were analysed a steady state tube furnace apparatus. The detection of the amino MDI derivative in the tar further supports the literature reports of a secondary decomposition mechanism where isocyanates trapped in the condensed phase are converted irreversibly into their amine derivatives. NBSIR 822604. 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. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. Hydrogen cyanide is approximately 25 times more toxic than carbon monoxide through the formation of the cyanide ion, which is formed by hydrolysis in the blood (Hartzell 1993). 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. After the initial stages of inert-atmosphere thermal decomposition where the polymer precursors are reformed and volatilised, the decomposition products tend to fragment into smaller molecules. 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). Fire Research Notes 951:p117. Terms and Conditions, 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. For example, Levin and coworkers reported that melamine-treated flexible polyurethane foam generated 6 times more HCN than an equal amount of non-melamine treated foam. The PIR foam produced similar HCN yields to the CMHR-PUF until 1.5, after which it increased more rapidly to give a yield of 20mgg1 at ~1.75. NIST performed the experimental burn tests 1 on 4-inch (10-cm) thick by 4 ft x 4 ft (1.2 m x 1.2 m) wide polyurethane foam slabs. 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. The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. The products generated in the flame zone then pass through the heated furnace tube, maintaining a high temperature, as in the upper layer of a compartment fire. In the case of flaming combustion, one of the most important factors relating to the toxic product yield is the fuel/air ratio which, as defined earlier, can be expressed as an equivalence ratio (). The two main market uses for polyurethane are in the furniture and interior industry and the construction industry with 28% and 25% of the market, respectively (Markets & Markets report 2011). The samples tested included both commercial rigid polyurethane foam and polyisocyanurate foam. 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. STM would like to acknowledge the University of Central Lancashire for provision of a studentship. Garrido and Font (2015) reported two main steps in the inert-atmosphere decomposition of flexible polyurethane foams. The resulting substituted urea can then react with another isocyanate to produce a biuret linkage (Scheme4). Other common diisocynates include hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI) and isophorone diisocyanate (IPDI) (Fig. However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. Off-gassing. Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. 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. Cyanide gas. This slight decrease is probably within the limits of experimental error, as it does not follow the general trend shown by most materials. Over 90% of all industrial polyurethanes are based on either TDI or MDI (Avar et al. Alongside this, the decomposition of the foam into an amine, alkene and carbon dioxide was also proposed. Fire and Materials 5(4):p133141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. Polyurethane foam, when burnt, gives off: Sulfuric acid Cyanide gas Ethane Phosphine. Using polyurethane indoors can expose you to fumes with a number of potential side effects. During these tests, the PIR was set up as wall panels covered on two faces with aluminium foil. Equation One analysis of fire victims' blood showed a trend of declining COHb and a rise in cyanide concentrations (Anderson et al. Building renovations, demolition, or building disassembly done years later can disturb spray foam insulation. In a letter to the editor of the journal, Barbrauskas et al. As with all foams, memory foam compresses under pressure. 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. Appropriate formulation affords a degree of control over the cross-linking in the polymer without the need for additional cross-linking agents. (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. 1982), and a three-compartment large scale test. 1982) to that of a large scale test room. This char can decompose further, leaving behind a residue at >800C, to produce simple organic fragments and some polycyclic aromatic hydrocarbons (PAHs). Rigid polyurethanes primarily produced aromatic compounds in the condensed phase products of decomposition, whereas flexible polyurethanes produced aromatics, alcohols, aldehydes and heterocycles. For both materials there is a clear increasein yield from the well-ventilated to under-ventilated conditions. (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. Based on this data, the HCN recovery fraction was calculated for both materials. In ventilation controlled fires (such as those occurring in a room, buildingor other enclosure), the yields of these gases from the flaming combustion of polyurethane foams generally follow the same trend. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. Various apparatus and protocols for quantifying fire effluent toxicity in different jurisdictions and industries have been critically reviewed (Hull & Paul 2007). P.J. 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. Suggested points of chain scission on a polyether polyol resulting in aldehydes, ketones and alkenes (Allan et al. Therefore, in certain conditions, polyurethanes foams can reach their auto-ignition temperature and ignite which will significantlyalter the effect the decomposition mechanisms and resulting products.

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