Equations2 and 3 have been taken from ISO 13571 (2007). 11, a conical heater used as a fire model is enclosed in a heat resistant glass chamber (400mm high with 300300mm base) so that the air flowaround the specimen may be controlledby diluting the oxygen content with nitrogen. In the gas phase, isocyanates, amines and yellow smoke will begin to decompose at >600C into low molecular weight nitrogen containing fragments (such as benzonitrile, aniline and hydrogen cyanide (HCN)). However, in the field of combustion toxicity testing, this under-ventilated burning is the most difficult to create using bench-scale apparatus. Additionally, NO was detected during the well-ventilated tests and NH3 during the under-ventilated tests. It is inexpensive and easy to install, however, it is a severe fire risk and requires a thermal barrier to make it safe. A large majority of the literature indicates that the addition of fire retardants does not increase toxicity of polyurethane foams. At 650C, the yield of HCN from the CMHR-PUF increased up to ~2.0 where it reached a peak of 14mg of HCN per gram of polymer burned. 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). The authors tested a rigid polyurethane foam using a NBS cup furnace (as described in Levin et al. (2014) on the catalytic decomposition of rigid polyurethane foam waste showed that ammonia, hydrogen cyanide and both nitrogen oxide and nitrogen dioxide were produced at temperatures up to 1100C. In a report from the same laboratory, Braun et al. Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. 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. The data was presented as material-LC50 values for 30min exposures with 14-day post-exposure of test animals and can be found in Tables10, 11 and 12. Fumes Tiny particles are produced from heating, volatilization, and condensation of metals (examples: zinc oxide fumes from welding of galvanized metal). Fire and Materials 6:p1315, Neviaser JL, Gann RG (2004) Evaluation of Toxic Potency values for Smoke from Products and Materials. 3 HCN yields reported in under-ventilated conditions vary depending on the composition of the material; with flexible foams producing less than rigid foams and polyisocyanurates producing the most overall. Springer Nature. At 850C the yield of HCN was higher with 16mgg1 at ~2.0. Recent work by Allan et al. International Association for Fire Safety Science, Ravey M, Pearce EM (1997) Flexible Polyurethane foam. Woolley WD, Wadley AI, Field P (1972) Studies of the thermal decomposition of flexible polyurethane foams in air. https://doi.org/10.1186/s40038-016-0012-3, DOI: https://doi.org/10.1186/s40038-016-0012-3. 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). In the UK, the rapid rise in fire deaths, in particular those from smoke toxicity, between the late 1950s and the early 1980s has been attributed to the rapid growth in low cost polyurethane foam furniture, with superior comfort and lower cost than the natural fillings that preceded it. 1 (1990) also reported increased HCN yields when the sample was allowed to smoulder before flaming in similar apparatus as above. Appropriate formulation affords a degree of control over the cross-linking in the polymer without the need for additional cross-linking agents. For example, polyurethane foam, when burned, gives off cyanide gas. A summary of the bond decomposition temperatures in polyurethanes is shown in Table2 (Gharehbagh & Ahmadi 2012). 2023 BioMed Central Ltd unless otherwise stated. Both authors read and approved the manuscript. Isocyanate structure also affects the reactivity of the isocyanate group. 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. Oxygen depletion can be lethal if the oxygen concentration falls below tenable levels (~6%). The FED is expressed as the sum of contributions to toxicity from individual species and normalised to 1g of fuel in 200L fire effluent, as used in BS 6853 (1999). 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. 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. The rigid polyurethane foam yielded ~55mgg1 CO and ~0.5mgg1 of HCN. 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). Combustion and Flame 146(12):p95108, Rogaume T, Bustamante-Valencia L, Guillaume E, Richard F, Luche J, Rein G, Torero JL (2011) Development of the Thermal Decomposition Mechanism of Polyether Polyurethane Foam Using Both Condensed and Gas-Phase Release Data. 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. The results showed a HCN yield of 15.8mgg1 at 600C. This is true of ALL polyurethane foam since it is an organic material, just like wood or cotton fabric. 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. 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. As polyurethane foams have very low thermal inertia, application of heat or a small flame can be enough to ignite them. 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. HAZWOPER 40 - Lesson 3 - Toxicology Flashcards | Quizlet (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. 1981), probably because of increased use of nitrogen-containing synthetic polymers. At >800C these compounds further fragment into simple molecules (such as HCN, CO, CH4 and CH2O) and PAHs. Further fragmentation of these molecules led to the production of HCN, acetonitrile, acrylonitrile and a range of olefinic fragments. PDF Fire Properties of Polyvinyl Chloride Neviaser and Gann (2004) compiled the toxic potency data for a range of materials including a number of fire retarded and non-fire retarded polyurethane foams. Work published as early as 1959 supported this mechanism of decomposition at higher temperatures and noted that up to 70% of the nitrogen in the foam could be converted to HCN at 1000C (Saunders 1959). The chemistry of polyurethane foams and their thermal decomposition are discussed in order to assess the relationship between the chemical and physical composition of the foam and the toxic products generated during their decomposition. One analysis of fire victims' blood showed a trend of declining COHb and a rise in cyanide concentrations (Anderson et al. California Privacy Statement, There are two reasons for this: The yields of the major toxic products (carbon monoxide (CO) and hydrogen cyanide (HCN)from N containing materials) will be much greater. Since serious fires involving the use of these materials have occurred on several ships, the United States Coast Guard has issued a Navigation and Vessel Inspection Circular No. 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. PDF The fire toxicity of polyurethane foams - SpringerOpen The higher flammability of these new furniture products took people by surprise, and has been blamed for an increased number of serious fires and a tripling of fire deaths over 20years (Fig. (2007) assessed the toxic product yields of a flexible polyurethane foam that was designed for use in hospital mattresses. 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. Spray Foam Insulation FAQs - Foam Kit Solutions ISO/TS 19700 (2013) Controlled equivalence ratio method for the determination of hazardous components of fire effluents the steady state tube furnace. 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. Fire Hazards of Insulation Materials | American Family Insurance Smouldering was forced by an electrically heated resistance wire embedded in the sample and a load cell measured the mass of the sample throughout the experiment. 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. MDI is a diaromatic diisocyanate compound that boils at 208C and is primarily used in the production of rigid foams. (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. The full size ISO 9705 test resulted in well-ventilated flaming ( 0.260.5) due to the relatively large volume of air and relatively small sample size. In others, under reduced oxygen concentrations, the fuel lifts from the surface, but ignition does not occur (Christy et al. Despite their name, the term polyurethane is used to describe a family of polymers whose monomers are joined by a range of functional groups primarily derived from the polyaddition of polyisocyanates and polyalcohols. polyurethane foam production and up to a point the amount of water added will be inversely proportional to the density of the foam. International Maritime Organisation, London, Garrido MA, Font R (2015) Pyrolysis and combustion study of flexible polyurethane foam. Fire Research Notes 951:p117. 1995). Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. 8). In a 12-square-foot area, urethane was totally burned off, but the rest suffered more minor damage. 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. Since HCN is a major contributor to the fire toxicity of polyurethane foams, the mechanisms by which they decompose are vital in understanding why they produce large-quantities of HCN during under-ventilated burning. The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. Polyurethane and polyisocyanate both release polyols and isocyanates during blowing, but the rates diminish rapidly over time as the product cures, provided they dialed in the temps & chemical mix correctly. p 1-30. These types of approaches have used existing rat lethality data, as described in ISO 13344 (1996) or more recently, based on the best available estimates of human toxicity thresholds as described in ISO 13571 (2007). Draeger tubes), conventional or Fourier transform infrared spectroscopy (FTIR) gas analysis, despite significant problems of reproducibility. The protocol has been modified as a toxicity test by the mass transport industries, in the aircraft (EN 2826 2011), maritime (Fire Test Procedure Code 2010), and railway tests (CEN/TS 455452 2009). These isocyanate derived cross-links can include biurets and allophanates (Fig. 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. 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. Insulation, like all building products, has an 'embodied' carbon footprint resulting from energy use during the manufacturing process. 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. 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. These nucleophiles include amines, alcohols, carboxylic acids, thiols, water, ureas and urethanes (Aneja 2002). I. However, no amines were detected in the vapour phase. Material composition, temperature and oxygen concentration are normally the most important. The reported yields for the tests performed can be found in Table8. While limited data were available regarding the flaming combustion of rigid polyurethane foams, the results were of a similar scale to those presented by Stec and Hull (2011). For both materials there is a clear increasein yield from the well-ventilated to under-ventilated conditions. Fire and Materials 19:p6164, Shufen L, Zhi J, Kaijun Y, Shuqin Y, Chow WK (2006) Studies on the Thermal Behavior of Polyurethanes. . Summing these contributions generates a fractional effective dose (FED). Early work by Woolley et al (1975) indicated that the decomposition of polyurethanes up to around 600C resulted in the volatilisation of fragmented polyurethane and subsequent release into a nitrogen rich yellow smoke, containing partially polymerised isocyanates and droplets of isocyanate from the foam. TRH wrote the fire toxicity section of the manuscript. Historically, material-LC50 data has been reported directly based on animal lethality testing, however due to the declining use of animal testing in fire toxicity assessment, calculations based on standard lethality data(such as ISO 13344 1996) are more commonly used. 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. A more recent assessment by Marsh and Gann (2013) tested a flexible polyurethane foam with a cotton polyester cover in a range of test methods including the radiant heat apparatus (NFPA 269 2012), the ISO 56592 (2012) smoke density chamber, a controlled atmosphere cone calorimeter (ASTM E 1354) and the steady state tube furnace (ISO/TS 19700 2013). 2), also results in cross-linking in the polymer. The toxic product yields may be quantified from the gas concentrations and mass feed rate during the steady state burn period. DiNenno et al., eds.). Gaithersberg, MD, Babrauskas V, Twilley WH, Janssens M, Yusa S (1992) Cone calorimeter for controlled-atmosphere studies. 1982), and a three-compartment large scale test. As polyols are prepolymers, their molecular mass is relevant to their application, with flexible foams being derived from 1000 to 6000 daltons and few hydroxyl groups, while those used in rigid foams have short chains from 250 to 1000 daltons with high functionality (312 hydroxyl groups per chain). TDI is primarily used in the production of flexible foams, which are used in the furniture and interior industries. In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanide. Equation2 represents the generally accepted case that there are only two significant asphyxiant fire gases, CO and HCN. 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. In many studies (such as those by Stec and Hull (2011), Purser and Purser (2008a) and Blomqvist et al. This was enough to cause deaths both during and post-exposure. Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. PDF Polyurethanes and Thermal Degradation Guidance Fire Res 1:p1121. Suggested points of chain scission on a polyether polyol resulting in aldehydes, ketones and alkenes (Allan et al. 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. The standard specifies four test conditions, but fails to link them to particular fire scenarios. Stec and Hull (2011) presented material-LC50 data for rigid polyurethane foam and polyisocyanurate foam, calculated using rat lethality data from ISO 13344 (1996). Download resource J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. In another investigation, using a steady state tube furnace, Blomqvist et al. This makes the isocyanate functional group highly reactive towards nucleophiles with an available hydrogen. The yield was much lower at 800C with 7.4mgg1 but at 1000C and 1200C the yield increased significantly to 33.9mgg1 and 48.1mgg1 respectively. What does polyurethane foam give off when burned? 11) ultimately giving well-ventilated flaming. 2013). When polyurethane and polystyrene burn, they create a very smoky fire that . The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). This is when flame retardant chemicals were added to the foam or coverings to stop the furniture from burning so ferociously. Is Polyurethane Foam Toxic, And Should You Avoid it? - The Safe Parent Instead polyureas were detected in the vapour phase and also in the condensed phase as a waxy, insoluble white substance. Research predicting the carbon monoxide evolution from flames of simple hydrocarbons, reviewed by Pitts (1995), has shown the importance of the equivalence ratio . Elemental analysis of the polymers showed that the CMHR-FPUR contained 8.22% nitrogen by weight and the PIR contained 6.15% nitrogen by weight. Fire Safety Journal 7:p11, Kavanagh BP, Pearl RG (1995) Inhaled nitric oxide in anesthesia and critical care medicine. Do memory foam mattresses give off toxic fumes? Non-fatal UK fire injuries requiring hospital treatment, 1955-2013 (UK Fire Statistics 2013). National Bureau of Standards, Gaithersburg, MD, Levin BC, Paabo M, Birky MM (1983b) Interlaboratory evaluation of the 1980 version of the national bureau of standards test method for assessing the acute inhalation toxicity of combustion products, NBSIR 832678, National Bureau of Standards, Gaithersberg, MD, Levin BC, Paabo M, Fultz ML, Bailey CS (1985) Generation of Hydrogen Cyanide from Flexible Polyurethane Foam Decomposed under Different Combustion Conditions. This is due to the concentration of oxygen directly under a flame being close or equal to 0% (Schartel & Hull 2007). The presence of oxygen in the atmosphere directly interacts with the solid phase, which accelerates decomposition. The time available for escape is the interval between the time of ignition and the time after which conditions become untenable, such that occupants can no longer take effective action to accomplish their own escape. That smell comes from volatile organic compounds, or VOCs, chemicals used in the mattress manufacturing process. Free of VOCs and HAPs. In most countries, there are no regulations covering the fire toxicity of building components, or for most road vehicles, including goods vehicles in tunnels. Hydrogen chloride (HCl) and hydrogen bromide (HBr) are strong acids which dissociate entirely in water. 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. Over 90% of all industrial polyurethanes are based on either TDI or MDI (Avar et al. (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. FIRE INVESTIGATOR REVIEWS Flashcards & Practice Test | Quizlet Their analysis indicated that, above 600C, the high temperature decomposition of MDI generated a large number of volatile fragments, including benzene, toluene, benzonitrile and toluonitrile. Fire and Materials 5(4):p133141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. Some methods have proved incapable of properlyreplicating the most toxic under-ventilated fire condition, where the yields of carbon monoxide and hydrogen cyanide are greatest, while other methods have shown good correlation with large scale test data. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. Fire Technology 51:p318, Blomqvist P, Lonnermark A (2001) Characterization of the combustion products in large-scale fire tests: comparison of three experimental configurations. In order to reduce the ignitability, and to a less extent the surface spread of flame and peak heat release rate, fire retardants are commonly added to commercial polyurethane foams in order to meet specific regulatory demands. ISO 56592 (2012) Plastics - Smoke generation - Part 2: Determination of optical density by a single-chamber test, ISO 56601 (2002) Fire tests Reaction to fire Part 1: Rate of heat release from building products (cone calorimeter method), ISO 9705 (1993) Fire tests Full-scale room tests for surface products, Kaplan HL (1987b) Effects of irritant gases on avoidance/escape performance and respiratory response of the baboon. (1981) on polycarbodiimides and polyureas enabled the determination of the source of the organonitriles and HCN during thermal decomposition. The resulting substituted urea can then react with another isocyanate to produce a biuret linkage (Scheme4). Combustion Science and Technology 183(7):p627644, Saunders JH (1959) the Reactions of Isocyanates and Isocyanate Derivatives at Elevated Temperatures. 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). 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). Other common diisocynates include hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI) and isophorone diisocyanate (IPDI) (Fig. The presence of Cu2O drastically decreased the yield of HCN in polyurethane foams at lower temperatures, but had little effect at high temperatures. 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 incapacitating Ct product corresponds to CO at a dose of 35 000LL1min (approximately equal to ppm min), predicting incapacitation at around 1200ppm for 30min exposure, and an exponential relationship for HCN (because asphyxiation by HCN exposure does not fit a linear relationship), predicting incapacitation at around 82ppm for 30min exposure. During flaming combustion, many fire retarded flexible polyurethane foams showed similar or slightly higher toxic potency than the non-fire retarded foams in both well-ventilated and under-ventilated conditions. Two mechanisms have been identified for the toxic effects of cyanide. Refer to MSDS. 1984a). The yields of CO and HCN from five bench-scale methods have been compared to large-scale data under a range of flaming fire conditions (Stec & Hull 2014). Full-scale fires simultaneously involve different fire stages in different places, which are changing with time. Common polyurethane functional groups i) urethane ii) urea iii) carbodiimide iv) uretdione v) isocyanurate. (such as polyurethane foam) burn slower (have a lower (HRR) than higher-density materials (cotton padding) of similar makeup. 2012). Overall, the report provides access to a large pool of data organised into a material-LC50 and also helps demonstrate that the large majority of data available is for well-ventilated tests.
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