polyurethane foam, when burned gives off

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). PubMedGoogle Scholar. Additionally, the self-addition of isocyanates to produce isocyanurates (v in Fig. Anal Bioanal Chem 387:p219236, Herrington R, Hock K (1998) Flexible Polyurethane Foams, 2nd edn. This is true of ALL polyurethane foam since it is an organic material, just like wood or cotton fabric. Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. 1999). However, from a fire toxicity perspective it is generally assumed that heat and other gases will have already prevented survival, while other toxicants such as CO or HCN, will be present in lethal quantities further from the fire where the oxygen depletion would not be considered harmful. VOCs have the ability to vaporize, or off-gas, at room temperature. 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. 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. 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. Experimental data reported a 28% recovery of DAT which supports the proposed decomposition mechanism. 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. I. The yields of toxic products followed the expected trend of being higher in the under-ventilated conditions. 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. thesis, Virginia Tech, p6-40, ASTM E 1354 Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter, ASTM E 662 Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials. CORE - Aggregating the world's open access research papers The authors asserted that fire retarding flexible polyurethane foam did not increase its acute or chronic toxicity when compared to non-fire retarded flexible foam. 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. They also asserted that the toxicity of the fire retarded foam was less than or equal to wood on a mass/mass basis and that wood contributes significantly more to residential fires in terms of fire smoke toxicity. Equations2 and 3 have been taken from ISO 13571 (2007). These fumes could lead to irritation of the eyes, throat, and lungs, and could cause more severe allergic reactions for individuals with chemical sensitivities. 2 (Avar et al. 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). ISO/TS 19700 (2013) Controlled equivalence ratio method for the determination of hazardous components of fire effluents the steady state tube furnace. The fire toxicity of polyurethane foams. J Ind Eng Chem 13(7):p11881194. J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. 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. The guidelines above for choosing a safer mattress or non toxic mattress topper can help determine which . Bench-scale methods used for generating toxic effluents from polyurethane foams have met with controversy. Fire and Materials 23:p171185, Hull TR, Paul KT (2007) Bench-scale assessment of combustion toxicity-A critical analysis of current protocols. Avar G, Meier WU, Casselmann H, Achten D (2012) Polymer Science: A Comprehensive Reference, Polymer Science: A Comprehensive Reference, 10, p411-441. An understanding of the relative reaction rates is vital in controlling the production of the polymer and producing the desired physical properties (Herrington & Hock 1998). SP Swedish National Testing and Research Institute, Bors, Hietaniemi J, Kallonen R, Mikkola E (1999) Burning characteristics of selected substances: Production of heat, smoke and chemical species. In this modification, the controlled atmosphere cone calorimeter (CACC) (Babrauskas et al. Journal of Fire and Materials 4:p5058, Farrar DG, Hartzell GE, Blank TL, Galster WA (1979) Development of a protocol for the assessment of the toxicity of combustion products resulting from the burning of cellular plastics, University of Utah Report, UTEC 79/130; RP-75-2-1 Renewal, RP-77-U-5. 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. The dangerous concentrations of some important toxic fire gases are shown in Table4 alongside the influence of ventilation condition on their yields. The authors reported GC/MS analysis of the condensed phase products obtained. Some of these methods attempt to address the transition through the fire stages by monitoring the formation of toxic gases as a function of time, as the oxygen concentration falls, and the fire condition changes from well-ventilated to under-ventilated. Equation 3 calculatesthe Fractional Effective Concentration (FEC) of sensory irritants in the fire effluent which limit escape. (1981) on polycarbodiimides and polyureas enabled the determination of the source of the organonitriles and HCN during thermal decomposition. The yields of acid gases and nitrogen-containing products depend upon the proportion of the appropriate elements in the materials burned and the efficiency of conversion. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). The resulting substituted urea can then react with another isocyanate to pro-duce a biuret linkage (Scheme 4). The data also does not specify the fire retardants used. (1972). (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam. P.J. The authors would like to thank Dr. Linda Bengtstrom for her contribution regarding the toxicity of isocyanates. 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. Most bench-scale methods have non-constant combustion conditions, such as those in closed chambers exposed to a constant source of heat, including the smoke density chamber (SDC) (ISO 56592 2012), and static tube furnace tests, such as the NF X 70100 (2006). 2008), where inhaled isocyanates rapidly form conjugates with epithelial lung cell proteins (Wisnewski et al. Thermal decomposition of polyurethanes is usually the reverse of polymerisation, resulting in the formation their precursor functional compoundsdiisocyanates, diamines and dihydroxy compounds. 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 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 Model 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. Off-gassing is the unpleasant odor caused by volatile . 1982), and a three . Terms and Conditions, DiNenno) Fourth Edition. 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. 2023 BioMed Central Ltd unless otherwise stated. However, the yield of CO was lower in both the non-flaming and flaming combustion. 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. The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. Bulky substituents that impinge on the isocyanate group can reduce its reactivity. (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. 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. Other fire retardants such as melamine are reported to significantly increase the HCN yield of polyurethane foams. Nitrogen dioxide dissolves rapidly in water to form nitric and nitrous acid. Suggested points of chain scission on a polyether polyol resulting in aldehydes, ketones and alkenes (Allan et al. Woolley WD, Wadley AI, Field P (1972) Studies of the thermal decomposition of flexible polyurethane foams in air. 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 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. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. Ask if the mattress materials are generally free of VOC and HAPs. Vilar Consultoria Tcnica Ltda, Rio de Janeiro, Voorhees J (1975) Extreme Toxicity from Combustion Products of Fire-Retarded Polyurethane Foam. However there was significant scattering of the results with both high and low outliers (26mgg1 at 1.22 and 9mgg1 at 1.95). 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. The authors declare that they have no competing interests. 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. Both of the materials showed a clear relationship with the HCN yield increasing with . Table1 shows the relative reactivity of isocyanates with nucleophiles at 25C without the presence of a catalyst. ISO 13571 (2007) considers the four major hazards from fire which may prevent escape (toxic gases, irritant gases, heat and smoke obscuration). For the range of materials investigated, the authors also noted that those containing fire retardants (including the CMHR-PUF and PIR) resulted in a higher recovery fraction of fuel N as HCN. In the smoke chamber, the highest reported yield during flaming combustion was 1.02mgg1. These reactions are accelerated in the presence of oxygen, which reduces the temperature of the decomposition steps. 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. 1982) to that of a large scale test room. The three compartments were connected by doors and the target room contained an open vent. 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 authors associated this with the effects of the Cu2O catalytically oxidising the HCN into N2, CO2, H2O and a small amount of nitrogen oxides. Correspondence to The polyester fabric produced 9293mgg1 of CO when burned with very little difference in the flaming or non-flaming conditions. Summing these contributions generates a fractional effective dose (FED). 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. DiNenno et al., eds.). 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. (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. . In a letter to the editor of the journal, Barbrauskas et al. Manage cookies/Do not sell my data we use in the preference centre. 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. Although the authors intended for the bench scale test methods and the large scale test to represent post-flashover room fires, the tests resulted in CO and HCN yields that suggested the combustion conditions were not under-ventilated (Table7). Provided by the Springer Nature SharedIt content-sharing initiative. The main asphyxiants, carbon monoxide and hydrogen cyanide have been widely studied and are the best understood (ISO 13571 2007). 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. It is likely that the fire toxicity of fire retarded polyurethane materials is largely dependent on the specific fire retardant present. As the toxic product yields of polyurethane foams are directly related to the ventilation conditions, so is the materials LC50 value. eff, should be used, rather than an averaged local equivalence ratio, based on the oxygen supply to the chamber, because, in some experiments, substantial secondary flaming occurred outside the test chamber, such that the amount of oxygen available to combustion exceeded the amount that was fed to the enclosed chamber. Journal of Applied Polymer Science 111:p11151143, Stec AA, Hull TR (2011) Assessment of the fire toxicity of building insulation materials. International Association for Fire Safety Science, Ravey M, Pearce EM (1997) Flexible Polyurethane foam. However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. 1 The authors compiled toxicological data from a range of primary online databases and also requests were made to collect unpublished data that were not publically available. The process of . Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. National Bureau of Standards, Washington D.C. Babrauskas V, Harris RH, Braun E, Levin BC, Paabo M, Gann RG (1991a) The role of bench-scale test data in assessing real-scale fire toxicity, Technical Note 1284, National Bureau of Standards and. Their apparently transient nature results from their very high reactivity with amines and their fairly high reactivity with water (which is almost always present in fire effluent). Rigid foam decomposed between 200 and 410C, while flexible foam decomposed between 150 to 500C. 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. 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. Various apparatus and protocols for quantifying fire effluent toxicity in different jurisdictions and industries have been critically reviewed (Hull & Paul 2007). The presence of oxygen in the atmosphere directly interacts with the solid phase, which accelerates decomposition. Research predicting the carbon monoxide evolution from flames of simple hydrocarbons, reviewed by Pitts (1995), has shown the importance of the equivalence ratio . The results indicated that the formation of the precursor, TDI, was much faster and preferable to depolymerisation when the volatile compounds could escape. 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. Primarily, isocyanates react with alcohols to produce urethane linkages in the polymer (Scheme1). 1995). 8-80, addressing . 2012). Routes of entry in this case are inhalation, ingestion (saliva), and skin absorption. Several authors have investigated the relationship between bench-scale test data and large-scale test data using polyurethane foams. Once the material ignited, the yield of HCN increased to 3.8mgg1. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme 5). Spray Foam Insulation: Helping Achieve Sustainability. A "combustion modified high resilience" flexible polyurethane foam (CMHR-PUF) and a polyisocyanurate (PIR) foam were analysed a steady state tube furnace apparatus. MathSciNet Interflam Conference Proceedings. 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. This is due to the concentration of oxygen directly under a flame being close or equal to 0% (Schartel & Hull 2007). Fire Science Reviews That smell comes from volatile organic compounds, or VOCs, chemicals used in the mattress manufacturing process. eds. 2005; Blomqvist & Lonnermark 2001). Fire and Materials 19:p6164, Shufen L, Zhi J, Kaijun Y, Shuqin Y, Chow WK (2006) Studies on the Thermal Behavior of Polyurethanes. 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. The Purser model, presented in equation1, uses \( {\mathrm{V}}_{{\mathrm{CO}}_2} \) a multiplication factor for CO2 driven by hyperventilation, therefore increasing the FED contribution from all the toxic species, and incorporates an acidosis factor A to account for toxicity of CO2 in its own right (ISO 13344 1996). p 102-120. 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. 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.

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