The heating of polyurethanes in an inert-atmosphere results in the progressive rupturing of bonds as a function of temperature. Additionally, a polyol-rich residue is left behind that begins to fragment and volatilise between 300 and 600C. 8 and Table3. The danger of using urethane products is when the foam burns. The interior of large flames are always under-ventilated, because oxygen cannot penetrate the flame. In an attempt to improve the understanding of the thermal decomposition of polyurethanes, Rogaume et al. Hydrogen chloride (HCl) and hydrogen bromide (HBr) are strong acids which dissociate entirely in water. Intermediate between these two approaches are those that can produce quasi-steady combustion conditions, such as the cone calorimeter (ISO 56601 2002) with non-standardised controlled atmosphere attachment (CACC), and the fire propagation apparatus (FPA) (ISO 12136 2011). statement and In a letter to the editor of the journal, Barbrauskas et al. This char can decompose further, leaving behind a residue at >800C, to produce simple organic fragments and some polycyclic aromatic hydrocarbons (PAHs). Carbon monoxide binds to the haemoglobin in red blood cells resulting in the formation of carboxyhaemoglobin (COHb), with stability 200 times greater than that of oxyhaemoglobin, impeding the transport of oxygen from the lungs to the cells in the body. The reported yields for the tests performed can be found in Table8. Fire Science Reviews 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 revised protocol is based on continuous sampling of the fire effluent. The yields of some of the most toxic gases from unwanted fires (such as CO, HCN and some organic irritants) have been demonstrated to be directly related to the combustion conditions (Purser 2002). The relation of the FED to the material-LC50 is given in equation4. 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. When a liquid fuel gives off enough vapors so that it can be ignited and burn, has reached its? The authors proposed that once formed, these compounds could partially polymerise with volatilised TDI in the vapour phase to produce Woolleys yellow smoke. Does Polyurethane Foam Give Off Toxic Fumes? | Nontoxic Living 2012). The authors acknowledged that further investigation of the steady state tube furnace was warranted as in some of the testing they suspected an instrumental error, since they were unable to account for roughly two-thirds of the total carbon from the sample and detected unusually low levels of CO2 during the under-ventilated tests. Cyanide gas. 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 sum of each of the concentrations multiplied by the exposure time, for each product; upper respiratory tract irritants are believed to depend on the concentration alone (Purser 2007). The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. 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. 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. NBSIR 822532. EN 2826. When a liquid fuel gives off enough vapors so that it can be . 1986). The polyurethane market was estimated to be worth $33 billion in 2010 and is expected to continue to grow to over $55 billion by 2016. A summary of the bond decomposition temperatures in polyurethanes is shown in Table2 (Gharehbagh & Ahmadi 2012). Isocyanates should be considered when assessing the fire toxicity of polyurethane foams, due to their acute irritating effects and chronic effects associated with exposure. Fire and Materials 11:p129, Paul KT, Hull TR, Lebek K, Stec AA (2008) Fire smoke toxicity: The effect of nitrogen oxides. The authors acknowledged the complexity of the decomposition of the material but were able to summarise it effectively in a 5-step mechanism (Fig. When formed at the site, there is a potential for a completed-operations exposure. 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. 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. 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. 2 (Avar et al. 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. This equation only relates to lethality, or cause of death. Woolley WD, Wadley AI, Field P (1972) Studies of the thermal decomposition of flexible polyurethane foams in air. Critical Reviews in Toxicology 32(4):259, Article 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. 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. The amount of nitrogen recovered from the char (8%) at 600C is of a similar order to the results reported by Purser and Purser (2008a) in the steady state tube furnace suggesting that the amount of nitrogen in the polyurethane foam converted into HCN when the material is allowed to smoulder first before flaming is similar to that of steady under-ventilated flaming. Equation Polyurethane Fume Exposure And Your Health: What You Need To Know During polymerisation, isocyanates undergo a number of distinct reactions. The authors did not specify which analytical methods were used in the quantification of the fire gases, only that they were sampled via a sampling bag. Similarly, the polyether based foam produced 15.1mgg1 to 28.1mgg1. \( \phi =\frac{actual\; fuel\;to\; air\; ratio}{stoichiometric\; fuel\;to\; air\; ratio} \). 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. Andersson B, Markert F, Holmstedt G (2005) Combustion products generated by hetero-organic fuels on four different fire test scales. Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. polyurethane foam production and up to a point the amount of water added will be inversely proportional to the density of the foam. Is the aging of urethane foams considered off-gassing? 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. In the smoke chamber, the highest reported yield during flaming combustion was 1.02mgg1. Thermosets are cross-linked polymer molecules which, on heating, do not melt but will eventually decompose. Heating of polyurethane foam while working on pipes Heating MDI-based glues Soldering Treatment with a heat gun Cutting with torches or hot wire Hot scissors Grinding Sawing It has been estimated that non-flaming thermal degradation of some polyurethane products may begin as low as about 150C (300F) to . 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). In addition to the more common process of adding cross-linking reagents during the production process, cross-linkages in polyurethanes can be the result of the high reactivity of the isocyanate precursors. The average well-ventilated yield of HCN was found to be 4mgg1, while it was 9mgg1 for under-ventilated conditions. The general approach in generating toxic potency data from chemical analysis is to assume additive behaviour of individual toxicants, and to express the concentration of each as its fraction of the lethal concentration for 50% of the population for a 30min exposure (gas-LC50). These substances can include carbon dioxide, carbon monoxide, formaldehyde, aldehydes, and other volatile organic compounds (VOCs), as well as soot and particulates. Draeger tubes), conventional or Fourier transform infrared spectroscopy (FTIR) gas analysis, despite significant problems of reproducibility. However, it does suggest that yield of toxic products is effected by covering the foam with another material during flaming combustion. Three Massachusetts Home Fires Linked to Spray-Foam Installation Acrolein and formaldehyde are formed especially from cellulosic materials under non-flaming decomposition conditions, but products of vitiated combustion contain other organic irritants. Both types of foam yielded very similar products at temperatures above 600C. Polymer International 53:p15851610. Heat, smoke and irritant gases may impair escape, increasing the risk of a lethal exposure to asphyxiant gases, andcan sometimes lung damage causes death in those managing to escape. 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. The reactivity of isocyanates with the various functional groups commonly present in the production of polyurethanes is dependent on both the steric and electronic factors of the R-group, and also the specific functional group the isocyanate is reacting with. 2011). PDF The fire toxicity of polyurethane foams - SpringerOpen 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. Based on this data, the HCN recovery fraction was calculated for both materials. 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). J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. 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. (such as polyurethane foam) burn slower (have a lower (HRR) than higher-density materials (cotton padding) of similar makeup. FED model from ISO 13571, Equation Correspondence to However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. When =1 the theoretical amount of air is available for complete combustion to carbon dioxide (CO2) and water. Ask if the mattress materials are generally free of VOC and HAPs. PDF Fire Properties of Polyvinyl Chloride Humans may react differently than animals exposed to toxic materials. Combustion Science and Technology 183(7):p627644, Saunders JH (1959) the Reactions of Isocyanates and Isocyanate Derivatives at Elevated Temperatures. 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. At lower temperatures, decomposition differs, depending on the composition and physical properties of the polymer, although clear trends can be identified. 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). Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. Top of Page. The authors intended to compare the HCN yields for the non-flaming and flaming combustion of the foam in a smoke chamber apparatus (as described in Levin et al. Relation of LC Brit Polym J 1:p203204, Braun E, Gann RG, Levin BC, Paabo M (1990) Combustion product toxic potency measurements: comparison of a small scale test and real-world fires. (2007). The full-scale test showed good accordance with the SSTF data considering the inherent unreliability of large-scale testing. Spray foam can potentially generate toxic emissions under these circumstances. 2008) and is 40kWm2 in the centre of the furnace at 650C and 78kWm2 at 825C. It has been designed to generate data for input to fire hazard assessments, using the methodology in ISO 13344 (1996) and ISO 13571 (2012), particularly in relation to the ISO fire stages. 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. The foam could be cleaned and a coating or metal cladding could be installed over it. PubMedGoogle Scholar. Using a cup furnace with a 200L sampling chamber (identical in design to the one used in the smoke chamber experiments), a 3.88g sample of foam was heated to just below its ignition temperature (370C) which yielded <1mgg1 HCN. Sub-ambient differential distillation of the remaining residue yielded a range of short-chain aldehydes (such as formaldehyde and acetaldehyde), ketones, alkenes and high molar mass polyol fragments. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100250mgg1. Other common diisocynates include hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI) and isophorone diisocyanate (IPDI) (Fig. The authors tested a rigid polyurethane foam using a NBS cup furnace (as described in Levin et al. Additionally, NO was detected during the well-ventilated tests and NH3 during the under-ventilated tests. (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. The applied heat flux must be large enough for burning to continue at oxygen concentrations as low as 5%. 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). The authors tested a rigid polyurethane foam using a NBS cup furnace (as described in Levin et al. Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. HCN also causes rapid incapacitation, preventing escape, and then, with CO, contributes to death from asphyxiation.
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