# polyurethane foam toxicity

J Ind Eng Chem 13(7):p1188–1194. A "combustion modified high resilience" flexible polyurethane foam (CMHR-PUF) and a polyisocyanurate (PIR) foam were analysed a steady state tube furnace apparatus. Toxicology 115:7, Henneken H, Vogel M, Karst U (2007) Determination of airborne isocyanates. Experimental data reported a 28 % recovery of DAT which supports the proposed decomposition mechanism. At 650 °C, the yield of HCN from the CMHR-PUF increased up to ϕ ~2.0 where it reached a peak of 14 mg of HCN per gram of polymer burned. Investigations by Woolley 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. Based on the temperature of the test, the yields of HCN are extremely low when compared with the CO yields. Similar to the human body, a polyurethane molecule is made up of 4 organic elements: oxygen, carbon, hydrogen and nitrogen. This will result in a HCN yield related that specific furnace temperature. This is due to the concentration of oxygen directly under a flame being close or equal to 0 % (Schartel & Hull 2007). The review refers to a publication by Babrauskas et al. 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). Taking this into consideration, the reported yields of isocyanates, aminoisocyanates and amines are still relevant, as the results of Blomqvist et al. Their analysis indicated that, above 600 °C, the high temperature decomposition of MDI generated a large number of volatile fragments, including benzene, toluene, benzonitrile and toluonitrile. At ϕ ~2.0 the CMHR-FPUR resulted in 8 % and 11 % nitrogen recovered as HCN for 650 °C and 850 °C respectively. The full-scale test showed good accordance with the SSTF data considering the inherent unreliability of large-scale testing. In a report from the same laboratory, Braun et al. The polyisocyanurate, on the other hand, produced slightly more HCN than the rigid foam (17 mg g−1 vs 12 mg g−1). This amine may then undergo further reaction with other isocyanates present to produce a urea (Scheme 3). More recent work by Shufen et al. 1982), and a three-compartment large scale test. Some blowing agents, for example, may produce toxic gases or residues that stay within the material, and may be released over time. The interior of large flames are always under-ventilated, because oxygen cannot penetrate the flame. 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. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. MDI and TDI both need to be handled carefully during the manufacturing process. By using this website, you agree to our Telephone: 314-872-8700 . combustion modified high resilience polyurethane foam, Alarie Y (2002) Toxicity of Fire Smoke. The open cone calorimeter replicates the early well-ventilated stage of flaming where a fire would be too small to produce enough toxicants to cause harm except in very small enclosures. Over short periods, inhaled CO impairs an individuals ability to escape, causing different effects at different concentrations. The average combined yield of isocyanates recovered was 0.869 mg g−1 and the average yield of amines and aminoisocyanates was 0.321 mg g−1. The specific mass of the polyurethane sample was not provided by the author and the ventilation conditions were not clear as a result of this. TNO Report. In addition, asphyxiation can also occur as a result of lowered oxygen concentration, and is affected by the carbon dioxide concentration. Aromatic diisocyanates, which are commonly used in the production of polyurethanes, have a slightly more complicated chemistry compared to monoiscyanates due to the electronic effects of two isocyanate groups. 1992), shown in Fig. Fire and Materials 6:p13–15, Neviaser JL, Gann RG (2004) Evaluation of Toxic Potency values for Smoke from Products and Materials. Thermal Decomposition of Polyether-based, Water-blown Commerical type of Flexible Polyurethane Foam. Nitric oxide (NO) and nitrogen dioxide (NO2) are non-flammable gases present in fire effluents. to FED. (2015) questioned their methodology and noted that the authors did not address the release of HCl and its contribution to the acute fire toxicity of the fire retarded foam. Article  ISO 5659–2 (2012) Plastics - Smoke generation - Part 2: Determination of optical density by a single-chamber test, ISO 5660–1 (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. Nitrogen dioxide dissolves rapidly in water to form nitric and nitrous acid. 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. 2. Stec and Hull (2011) presented material-LC50 data for rigid polyurethane foam and polyisocyanurate foam, calculated using rat lethality data from ISO 13344 (1996). Polyols are binding compounds that are essential to creating the polyurethane foam. It is not intended to be a critical evaluation of the various test methods or procedures used or the data obtained using these methodologies. Gaithersberg, MD, Babrauskas V, Twilley WH, Janssens M, Yusa S (1992) Cone calorimeter for controlled-atmosphere studies. In the chamber, 0.23 g of black char and 0.04 g of yellow oil were recovered. Toxicity occurs only during manufacture and curing. Ureas and urethanes decompose between 160 and 200 °C. (1972). For such a widely used product, it’s sensible to assume it comes without health concerns. The polyester based foam produced nearly double the amount of HCN between 900 and 1000 °C than the polyether foam with an increase from 20.8 mg g−1 to 38.0 mg g−1. 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. The polyurethanes used were elastomers based on TDI, which could potentially have differing decomposition mechanisms to their foam counterparts. A large majority of the literature indicates that the addition of fire retardants does not increase toxicity of polyurethane foams. Therefore the contribution of HCN to fire deaths is difficult to assess, and analysis for CN− is limited to cases where lethal concentrations of CO are absent. Early work by Woolley et al (1975) indicated that the decomposition of polyurethanes up to around 600 °C 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. In China and Japan, there are specific restrictions on the use of materials with high fire toxicity in high risk applications such as tall buildings, while an increasing number of jurisdictions permit the alternative performance based design approaches to fire safety. Part of 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. 1). Taking this into consideration, the steady state tube furnace and the controlled atmosphere cone calorimeter both produced the highest yields of HCN in under-ventilated conditions. A polyether polyol (i) and a polyester polyol (ii). 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. When ϕ = 1 the theoretical amount of air is available for complete combustion to carbon dioxide (CO2) and water. 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. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100–250 mg g−1. HCN analysis was performed using infrared (IR) spectroscopy using a short path-length gas cell, which is a questionable method for the quantification of HCN due to its poor IR absorption, high potential for interferences and a poor limit of detection. 9). Several authors have investigated the relationship between bench-scale test data and large-scale test data using polyurethane foams. From this, the library of data was sorted into categories of combustion/pyrolysis conditions, material/product, type of test animal and toxicological endpoint. (1972) suggested that the decomposition was initiated by the release of a nitrogen-rich material at 200–300 °C which in turn decomposes into low molecular weight nitrogenous fragments above 500 °C. Equation 2 calculates the FED of the major asphyxiants, CO and HCN, but without taking oxygen depletion or CO2 driven hyperventilation into account. Equations 2 and 3 have been taken from ISO 13571 (2007). The relation of the FED to the material-LC50 is given in equation 4. The most notable and abundant of these was hydrogen cyanide which increased in yield from 700 to 1000 °C. Over 90 % of all industrial polyurethanes are based on either TDI or MDI (Avar et al. Apparatus where ϕ changes rapidly allow little time for sampling and measurement of mass loss and effluent composition at a specific value of ϕ, with resultant errors and uncertainties. When introduced into the polyurethane chemistry, water will react chemically to form small bubbles of carbon dioxide. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. The effects range from tears and reflex blinking of the eyes, pain in the nose, throat and chest, breath-holding, coughing, excessive secretion of mucus, to bronchoconstriction and laryngeal spasms (Purser 2008b). 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. Alongside the experiments performed in the steady state tube furnace, the PIR was also investigated in a half scale ISO 9705 room-corridor test and in a full size ISO 9705 (1993) room. It has been suggested that the reproducibility problems arise from the single point measurement (the tip of the probe may be in the centre of the plume, below it, or if mixing is more efficient, the upper layer may be recirculated through the flame), or the timing of the effluent sampling may cause instabilities (for example an initial proposal to sample after 8 min was replaced by a proposal to sample when the smoke density reached its maximum). The relatively high yields of CO from under-ventilated fires are held responsible for most deaths through inhalation of smoke and toxic gases. The reaction of an isocyanate functional group with water (Scheme 2) results in the formation of an unstable carbamic acid group, which in turn decomposes to release an amine and carbon dioxide. Isocyanates are a highly reactive family of compounds that are characterised by the R − N = C = O functional group (where R can be any aliphatic or aromatic functionality). Similarly, Busker et al. Additionally, the amount of CO generated for both materials began to taper off at ϕ 1.2-2.0 as the available oxygen becomes so low that the generation of CO becomes limited, while the yield of HCN continues to increase with equivalence ratio and temperature. Unfortunately, research suggests that’s not the case. The yields of CO and HCN at varying ϕ and temperature are presented in Table 5. Technology, Gaithersburg MD, Babrauskas V, Levin BC, Gann R, Paabo M, Harris RH, Peacock RD, Yusa S (1991b) Toxic potency measurement for fire hazard analysis, special publication 827, National Institute of Standards and Technology. Recent work by Allan et al. TRH wrote the fire toxicity section of the manuscript. Data from large scale fires in enclosures, such as a room, shows much higher levels of the two of the major toxicants, carbon monoxide (CO) and hydrogen cyanide (HCN) under conditions of developed flaming (Andersson et al. For both materials there is a clear increase in yield from the well-ventilated to under-ventilated conditions. LC50 values should be referenced to the fire condition under which they were measured. Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. Summing these contributions generates a fractional effective dose (FED). Over this period there was a corresponding shift from the main cause of death in fires being attributed to “burns” to being attributed to “inhalation of smoke and toxic gases”. When a one gram sample of foam was decomposed in air, CO was formed at a lower temperature than in nitrogen (300 °C vs 400 °C), with a relative concentration of 5000 ppm at 500 °C. Woolley WD, Fardell PJ, Buckland IG (1975) The Thermal Decomposition Products of Rigid Polyurethane. 4)). The samples tested included both commercial rigid polyurethane foam and polyisocyanurate foam. 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. 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. ISO/TS 19700 (2013) Controlled equivalence ratio method for the determination of hazardous components of fire effluents – the steady state tube furnace. STM wrote the manuscript and produced all of the images used in figures. However, as the fire condition became under-ventilated (ϕ > 1.5), the yields of both CO and HCN increased for both rigid polyurethane and the polyisocyanurate, while the yields of CO2 and NO2 decreased. Additionally, NO was detected during the well-ventilated tests and NH3 during the under-ventilated tests. 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. An equivalence ratio of 0.5 represents a well-ventilated scenario, typical of an early growing fire, while a ratio of 2 corresponds to the under-ventilated stage responsible for high yields of toxic effluents. However, while the char produced when the polymer was heated at 370 °C contained only 20 % of the total nitrogen from the polymer, 40 % of that (8 % of the total nitrogen in the polymer) was recovered as HCN when the char was burned at 600 °C. Both of the materials showed a clear relationship with the HCN yield increasing with ϕ. Toxicity Assessment of Products of Combustion of Flexible Polyurethane Foam CRAIG BEYLER Hughes Associates, Inc. 3610 Commerce Drive, Suite 817 Baltimore, MD 21227 USA ABSTRACT The scientific literature on the toxicity of products of combustion of flexible polyurethane foam is reviewed to assess its potential for use in toxic hazard analysis. Ann occup Hyg 19:269–273, Levchik SV, Weil ED (2004) Thermal Decomposition, combustion and fire-retardancy of polyurethanes - a review of the recent literature. The toxic product generation during flaming combustion of polyurethane foams is reviewed, in order to relate the yields of toxic products and the overall fire toxicity to the fire conditions. hbspt.cta._relativeUrls=true;hbspt.cta.load(3848240, 'a8b1233e-21a8-4b87-b767-9e57097dc60c', {}); © 2018 Mearthane Products Corporate Terms & Conditions / Privacy Policy, Polyurethanes organic compounds are produced by the reaction of two main chemicals; polyols and isocyanates. National Fire Protection Association, Quincy, pp 2–83, Purser DA (2007) The application of exposure concentration and dose to evaluation of effects of irritants as components of fire hazard. (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. 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. 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 (Table 7). 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. Polyurethane Spray Foam insulation research has pointed towards it having adverse effects on the health, and the chemicals contain high levels of toxic material. DiNenno et al. Combustion Science and Technology 183(7):p627–644, Saunders JH (1959) the Reactions of Isocyanates and Isocyanate Derivatives at Elevated Temperatures. 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). 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. PML 1998-A97. 1981), probably because of increased use of nitrogen-containing synthetic polymers. Springer Nature. CEN/TS 45545–2 (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. $$\begin{array}{l}\mathrm{FED}=\left\{\frac{\left[\mathrm{C}\mathrm{O}\right]}{{\mathrm{LC}}_{50,\;\mathrm{C}\mathrm{O}}}+\frac{\left[\mathrm{H}\mathrm{C}\mathrm{N}\right]}{{\mathrm{LC}}_{50,\;\mathrm{H}\mathrm{C}\mathrm{N}}}+\frac{\left[\mathrm{A}\mathrm{G}\mathrm{I}\right]}{{\mathrm{LC}}_{50,\;\mathrm{A}\mathrm{G}\mathrm{I}}}+\frac{\left[\mathrm{O}\mathrm{I}\right]}{{\mathrm{LC}}_{50,\;\mathrm{O}\mathrm{I}}}\dots \right\}\times {\mathrm{V}}_{{\mathrm{CO}}_2}+\mathrm{A}+\frac{21-\left[{\mathrm{O}}_2\right]}{21-5.4}\\ {}{\mathrm{V}}_{{\mathrm{CO}}_2}=1\kern0.36em +\kern0.36em \frac{ \exp \left(0.14\left[{\mathrm{CO}}_2\right]\right)-1}{2}\end{array}$$, $$\mathrm{FED}={\displaystyle \sum_{t_1}^{t_2}\frac{\left[\mathrm{C}\mathrm{O}\right]}{35\;000}}\;\Delta t+{\displaystyle \sum_{t_1}^{t_2}\frac{ \exp \left(\left[\mathrm{H}\mathrm{C}\mathrm{N}\right]/43\right)}{220}}\;\Delta t$$, $$\mathrm{F}\mathrm{E}\mathrm{C}=\frac{\left[\mathrm{H}\mathrm{C}\mathrm{l}\right]}{{\mathrm{IC}}_{50,\;\mathrm{H}\mathrm{C}\mathrm{l}}}+\frac{\left[\mathrm{H}\mathrm{B}\mathrm{r}\right]}{{\mathrm{IC}}_{50,\;\mathrm{H}\mathrm{B}\mathrm{r}}}+\frac{\left[\mathrm{H}\mathrm{F}\right]}{{\mathrm{IC}}_{50,\;\mathrm{H}\mathrm{F}}}+\frac{\left[{\mathrm{SO}}_2\right]}{{\mathrm{IC}}_{50,\;{\mathrm{SO}}_2}}+\frac{\left[{\mathrm{NO}}_2\right]}{{\mathrm{IC}}_{50,\;{\mathrm{NO}}_2}}+\frac{\left[\mathrm{acrolein}\right]}{{\mathrm{IC}}_{50,\;\mathrm{acrolein}}}+\frac{\left[\mathrm{fomaldehyde}\right]}{{\mathrm{IC}}_{50,\;\mathrm{fomaldehyde}}}+{\displaystyle \sum \frac{\left[\mathrm{irritant}\right]}{{\mathrm{IC}}_{50,\;\mathrm{irritant}}}}$$, $$\mathrm{material}\hbox{-} {\mathrm{LC}}_{50}=\kern0.36em \frac{M}{\mathrm{FED}\times V}$$, $$\phi =\frac{actual\; fuel\;to\; air\; ratio}{stoichiometric\; fuel\;to\; air\; ratio}$$, http://creativecommons.org/licenses/by/4.0/, https://doi.org/10.1186/s40038-016-0012-3. National Bureau of Standards, Washington D.C. Levin BC, Paabo M, Fultz ML, Bailey C, Yin W, Harris SE (1983a) Acute inhalation toxicological evaluation of combustion products from fire-retarded and non-fire retarded flexible polyurethane foam and polyester. 9). ϕ depends on the mass loss rate of the specimen and the available air; for most methods one or both are unknown; ϕ will be increased by an unknown factor if products are recirculated into the flame zone. These bubbles are what create the cellular structure of the foam, which can be open cells or closed cells. 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. 3) (Aneja 2002). For a fixed chamber volume (0.51 m3), 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. 1982), the authors exposed male Fisher 344 rats in a 200 L exposure chamber to the fire effluent from the flaming and non-flaming combustion of both materials. During the study, scientists utilized lab rats to breath in the fumes for a certain period of time. Many foams use greenhouse gases as blowing agents, and thus must comply with legal guidelines mandating thickness levels and distribution arrays. In this post, we will explore the toxicity of thermoset polyurethanes and the factors that may cause polyurethanes to be toxic or not. Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. 13) (UK Fire Statistics 2013). The authors noted that the yields of CO during the well-ventilated testing were higher than expected for both materials, and attributed this to the possible presence of gas phase free radical quenchers, such as halogens or phosphorous containing flame retardants, which would reduce the conversion of CO to CO2 (Schnipper & Smith-Hansen 1995). Relation of LC A summary of these results can be found in Table 9. This can be explained by the fragmentation of nitrogen containing organics in the flame and in the effluent, as suggested by studies of the inert-atmosphere decomposition of polyurethane materials. To learn more about the different types of foams and how they are produced, make sure to check out our ". 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 overall toxicity of the polyisocyanurate foam shows a clear increase as the fire became more under-ventilated, while the rigid polyurethane foam showed a slight decrease at ϕ 1.24—2.00. A large number of studies have been performed over the last 50 years to understand the thermal decomposition of polyurethane materials, and as a result of this the mechanism of their decomposition in inert-atmospheres is fairly well understood. Two mechanisms have been identified for the toxic effects of cyanide. Various apparatus and protocols for quantifying fire effluent toxicity in different jurisdictions and industries have been critically reviewed (Hull & Paul 2007). Farrar DG, Galster WA (1980) Biological end-points for the assessment of the toxicity of products of combustion of material. This report presents a comprehensive literature review of the toxicity of the combustion products of flexible polyurethane foam and the thermal decomposition products of this polymer. 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. 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. The authors noted that the total concentrations of CO and HCN during flaming combustion were greater than the sum of those from the individual materials. Only the SSTF has a heated reaction zone which replicates the hot layer. Hietaniemi et al. Google Scholar, Schartel B, Hull TR (2007) Development of fire-retarded materials - interpretation of cone calorimeter data. 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. In terms of hazard, carbon monoxide (CO) is typically the most abundant toxicant in fires under almost all combustion conditions. Purser model, [AGI] is the concentration of inorganic acid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2] × 0.05. A more recent review, by Levchik and Weil (2004), assessed the decomposition, combustion and fire-retardancy of polyurethanes. Higher temperatures resulted in the volatilisation of most of the polyurethane precursors via the formation of lower molecular weight compounds. Polymer-Plastics Technology and Engineering 45:p95–108, Singh H, Jain AK (2009) Ignition, Combustion, Toxicity, and Fire Retardancy of Polyurethane Foams: A Comprehensive Review. CO yields are generally very low for well-ventilated conditions (in the absence of halogens) but increase considerably under-ventilated combustion conditions. 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 5659–2 2012) to assess the toxicity. Uncoated foam “rusts” (forms a brown dusty layer). The dangerous concentrations of some important toxic fire gases are shown in Table 4 alongside the influence of ventilation condition on their yields. In some bench-scale apparatus the heat flux is constant, and often insufficient to sustain flaming at such low oxygen concentrations; further, an unknown quantity of fresh air bypasses the fire plume, so the ventilation condition, and hence ϕ, remains undefined. (1972) noted that the yellow smoke was produced up to around 600 °C, where it would then decompose to give a family of low molecular weight, nitrogen containing products including hydrogen cyanide, acetonitrile, acrylonitrile, pyridine, and benzonitrile. The authors would like to thank Dr. Linda Bengtstrom for her contribution regarding the toxicity of isocyanates. Journal of Fire and Materials 4:p50–58, 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. 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. 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. 1986). The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. 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. Urethane foam is everywhere — it’s under your carpet, in your furniture and your bed, in your walls, on the soles of your shoes and in your athletic helmet. Additionally, the authors reported a yield of 13–15 mg g−1 of CO, 1.4–1.5 mg g−1 of HCN, and 10–12 mg g−1 of NO. Bulky substituents that impinge on the isocyanate group can reduce its reactivity. This resulted in the reported HCN yields for the under-ventilated conditions being lower than expected in all of the tests. 2011). 4). Isocyanates were primarily produced during the first stage, and in the second stage primarily carbonyls (R2-C = O) and hydrocarbons were detected using infrared analysis. Isocyanate structure also affects the reactivity of the isocyanate group. 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. 2012). 2013). LAST-A-FOAM ® rigid CFC-free polyurethane foam boards and products are cost-effective, versatile, strong and durable. Isocyanates also react with themselves in various ways to produce dimers, trimers and completely new functional groups.