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. VOCs have the ability to vaporize, or off-gas, at room temperature. Spray foam can potentially generate toxic emissions under these circumstances. (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. 1982), and a three . 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. Additionally, the amount of CO generated for both materials began to taper off at 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. Anal Bioanal Chem 387:p219236, Herrington R, Hock K (1998) Flexible Polyurethane Foams, 2nd edn. Therefore, the products of decomposition can be predicted from the composition of the polymer. Is Polyurethane Foam Toxic, And Should You Avoid it? - The Safe Parent The second results in a brief stimulation, followed by severe depression, of respiratory frequency, also starving the body of oxygen, and causing convulsions, respiratory arrest and death (Alarie 2002). 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. The authors acknowledged that they did not include isocyanates in their calculations. Primarily, isocyanates react with alcohols to produce urethane linkages in the polymer (Scheme1). 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 review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. 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. (2007). J Allergy Clin Immunol 104:p341347, Woolley WD, Fardell PJ (1977) The prediction of combustion products. In most countries, there are no regulations covering the fire toxicity of building components, or for most road vehicles, including goods vehicles in tunnels. Levin BC, Fowell AJ, Birky MM, Paabo M, Stolte A, Malek D (1982) Further development of a test method for the assessment of the acute inhalation toxicity of combustion products. The fire toxicity of polyurethane foams. 50 A summary of these results can be found in Table9. 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. Work by Ravey and Pearce (1997) on the decomposition of a polyether based flexible polyurethane foam suggested that up to 360C the decomposition of the foam was achieved by two main mechanisms. Resources & Documents Library 2 2005; Blomqvist & Lonnermark 2001). At >800C these compounds further fragment into simple molecules (such as HCN, CO, CH4 and CH2O) and PAHs. The trimerisation results in a highly stable isocyanurate ring which confer additional thermalstability to polyisocyanurates (Scheme7). Additionally, the authors suggested the positions on the polyol chain where bond scission could occur, explaining the presence of the short-chain alkenes, aldehydes and ketones (Scheme9). Each method is described briefly in the following section. p 102-120. At a CO concentration of 10 ppm, impairment of judgement and visual perception occur; exposure to 100 ppm causes dizziness, headache, and weariness; loss of consciousness occurs at 250 ppm; and 1000 ppm results in rapid death. Isocyanate derived functional groups that cross-link polyurethane chains i) biurets ii) allophanates. The non-flaming decomposition of non-fire retarded polyurethane foams in air is generally quite well understood and comparable to the inert atmosphere decomposition, in terms of both products and mechanisms. Fire Safety Journal 40:439465, Aneja A (2002) Chapter 2, Structureproperty Relationships of Flexible Polyurethane Foams, PhD. Stec and Hull (2011) assessed the fire toxicity of building insulation materials using a steady state tube furnace asdescribed in ISO/TS 19700 (2013). Cookies policy. Two mechanisms have been identified for the toxic effects of cyanide. 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. Using a smoke chamber set up for animal exposure experiments (as described in Levin et al. Draeger tubes), conventional or Fourier transform infrared spectroscopy (FTIR) gas analysis, despite significant problems of reproducibility. Humans may react differently than animals exposed to toxic materials. 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 Steady state tube furnace apparatus, ISO/TS 19700. National Fire Protection Association, Quincy, pp 283, Purser DA (2007) The application of exposure concentration and dose to evaluation of effects of irritants as components of fire hazard. 8 and Table3. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100250mgg1. The yields of CO and HCN at varying and temperature are presented in Table5. The initial decomposition of the foam, at >300C, results in the volatilisation of isocyanates, amines and Woolleys yellow smoke, leaving behind polyols in the condensed phase. In this modification, the controlled atmosphere cone calorimeter (CACC) (Babrauskas et al. Further fragmentation of these molecules led to the production of HCN, acetonitrile, acrylonitrile and a range of olefinic fragments. The difference with other polyurethane foams is that memory foam also contains added chemicals that increase its viscosity and elasticity, hence its alternate name, viscoelastic foam. It is therefore essential to the assessment of toxic hazard from fire that each fire stage can be adequately replicated, and preferably the individual fire stages treated separately. Journal of Analytical and Applied pyrolysis 108:p143150, Hartzell G (1993) Overview of Combustion Toxicology. The authors tested a rigid polyurethane foam using a NBS cup furnace (as described in Levin et al. FED model from ISO 13571, Equation Polymer International 53:p15851610. Relation of LC Flaming combustion of the polyurethane foam did not cause any animal deaths, however the non-flaming combustion resulted in deaths post-exposure. It can continue to irritate people sensitive to chemicals or odors . Full-scale fires simultaneously involve different fire stages in different places, which are changing with time. While this may occur to some degree, it is generally accepted that the majority of the diisocyanates produced in the decomposition of polyurethanes are either volatilised or converted into their amine derivative and then volatilised. 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. Science 187:p742744, Wisnewski AV, Lemus R, Karol MH, Redlich CA (1999) Isocyanate-conjugated human lung epithelial cell proteins: A link between exposure and asthma? Thermosets are cross-linked polymer molecules which, on heating, do not melt but will eventually decompose. 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). Stec and Hull (2011) presented material-LC50 data for rigid polyurethane foam and polyisocyanurate foam, calculated using rat lethality data from ISO 13344 (1996). 2012). Progressive changes in the composition of a static specimen (for example due to char formation) provide additional complexity. (2007)), the sample is raised to a fixed furnace temperature, which is further increased in the gas phase during flaming combustion. 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. Refer to MSDS. At sufficiently high concentrations, or when attached to submicron particles, such as soot, most irritants can penetrate deeper into the lungs, causing pulmonary irritation effects which may cause post-exposure respiratory distress and death, generally occurring from a few hours to several days after exposure, due to pulmonary oedema (flooding of the lungs) (ISO 13571 2007). 2011). These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. Common polyurethane functional groups i) urethane ii) urea iii) carbodiimide iv) uretdione v) isocyanurate. 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. Fire and Materials 31:p495521, Bott B, Firth JG, Jones TA (1969) Evolution of toxic gases from heated plastics. The significant increased yields at 1000C and 1200C could also be attributed to pyrolysis of the nitrogenous combustion products into HCN due to the low air flow rate. PML 1998-A97. CORE - Aggregating the world's open access research papers In a letter to the editor of the journal, Barbrauskas et al. 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. Various apparatus and protocols for quantifying fire effluent toxicity in different jurisdictions and industries have been critically reviewed (Hull & Paul 2007). 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. 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. Short chains with high functionality results in highly cross-linked polyurethane polymers which is characteristic of rigid foams. The first being a depolymerisation which would dissociate the polymer to isocyanates and alcohols, the second being dissociation to a primary amine, an olefin and carbon dioxide. California Privacy Statement, The cribs used in the ISO 9705 tests were constructed from PIR sticks which burned rapidly, albeit with minimal damage to the room. The FED value is calculated using the exposed dose relationship (concentration-time product, Ct) for CO. This suggests that the nitrogen in the char will more readily form HCN, even when the flaming is well-ventilated. The NFX generates data intermediate between the well-ventilated and under-ventilated fire conditions. While there were some problems, the data does show that the yields of toxicants from the polyurethane foam were generally most representative of post-flashover conditions in the test methods that were designed for ventilation controlled conditions, such as the steady state tube furnace and the controlled atmosphere cone calorimeter. NBSIR 822532. When polyurethane foam is burned, it gives off a wide variety of potentially harmful substances. Syntheticpolymeric materials may be divided into thermoplastics and thermosets. (1999) used the controlled atmosphere cone calorimeter, but argues correctly,in the authors' opinion,that an instantaneous effective global equivalence ratio STM wrote the manuscript and produced all of the images used in figures. Additionally, a polyol-rich residue is left behind that begins to fragment and volatilise between 300 and 600C. Research predicting the carbon monoxide evolution from flames of simple hydrocarbons, reviewed by Pitts (1995), has shown the importance of the equivalence ratio . It is usually used in isomeric mixtures of varying ratios, with 80:20 2,4 to 2,6 being the most commonly used (Fig. Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. The highest concentration these compounds were formed at occurred at a decomposition temperature of 350400C which indicated no new degradation steps had occurred beyond 350C. 1999). Ureas and urethanes decompose between 160 and 200C. 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. (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. Toxicology 47:165170, Kaplan HL, Grand AF, Hartzell GE (1984a) Toxicity and the smoke problem. However, the lower yields can be attributed to the fact that the cone calorimeter is a well-ventilated scenario, estimated as ~0.7 (Schartel & Hull 2007). The rigid polyurethane foam yielded ~55mgg1 CO and ~0.5mgg1 of HCN. However, once one of the groups forms a urethane or urea, the activating effect on the other isocyanate is reduced, as ureas and urethanes are weaker activating groups than isocyanates. Results from these burn tests are used for comparison with the model developed to simulate flame spread, heat fluxes, and smoke development over time (Figure 1). Whether one or other of these mechanisms predominates, or their interrelationship, remains unclear. Hietaniemi et al. Part of 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. 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. The toxic product yields may be quantified from the gas concentrations and mass feed rate during the steady state burn period. 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. Taking this into consideration, the reported yields of isocyanates, aminoisocyanates and amines are still relevant, as the results of Blomqvist et al. From this, the library of data was sorted into categories of combustion/pyrolysis conditions, material/product, type of test animal and toxicological endpoint. Journal of Fire Sciences 8:p6379, BS 6853 (1999) Code of practise for fire precautions in the design and construction of passenger carrying trains. Energy and Buildings 43:p498506, Stec AA, Hull TR (2014) Fire Toxicity Assessment: Comparison of Asphyxiant Yields from Laboratory and Large Scale Flaming Fires. Fire Res 1:p1121. But many products or materials continue off-gassing even after the "new smell" has gone awaythe fumes are just much more subtle. The authors suggested that the presence of oxygen does not affect the mechanisms by which CO and HCN are produced. Both may be present in fire effluent, for example from PVC or halogenated flame retardants, and since the damage caused by the acidity (the concentration of H+ ions) is independent of the specificanion (Cl or Br), the discussion on HCl is also applicable to HBr. \( \phi =\frac{actual\; fuel\;to\; air\; ratio}{stoichiometric\; fuel\;to\; air\; ratio} \). (1990) also reported increased HCN yields when the sample was allowed to smoulder before flaming in similar apparatus as above. 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 test room was 2.43.03.0m with a door (dimensions not specified) and a 1 to 2kg slab of foam in the centre of the room. Their development continued commercially in Germany, eventually leading to a global multibillion dollar industry (Vilar 2002). 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. Fire Hazards Of Polyurethane Foam - Klausbruckner ISO 13571 (2007) considers the four major hazards from fire which may prevent escape (toxic gases, irritant gases, heat and smoke obscuration). Animal studies provide most of what we know about the dangerous effects of toxic substances. 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. If exposed to sufficient heat and flame, polyurethane foam will burn. Nitric oxide (NO) and nitrogen dioxide (NO2) are non-flammable gases present in fire effluents. 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)). Journal of Applied Polymer Science 111:p11151143, Stec AA, Hull TR (2011) Assessment of the fire toxicity of building insulation materials. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). An FED equal to one indicates that the sum of concentrations of individual species will be lethal to 50% of the population over a 30min exposure. 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. (2006) and also Garrido and Font (2015). These yields are comparable to that of the results reported by Blomqvist et al. The authors noted that the polyester polyols were more stable than the polyether polyols, with the latter fragmenting at a lower temperature (300400C). The severity of the effects increases with dose (Hartzell 1993). 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). (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. A summary of these structures is shown in Fig. 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. In particular, reports that used non-standard tube furnace apparatus lacked sufficient information about the conditions of the experiment and as such were not included. 2 (Avar et al. decomposition products will burn. The increased yield of HCN for the CMHR-FPUR between 650C and 850C is likely due to the increased fragmentation of nitrogenous organic compounds in the flame, similar to the behaviour during non-flaming combustion in air reported by Woolley et al. Hydrogen cyanide is approximately 25 times more toxic than carbon monoxide through the formation of the cyanide ion, which is formed by hydrolysis in the blood (Hartzell 1993). 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. (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. Critical Reviews in Toxicology 32(4):259, Article Tests were carried out on the CMHR-PUF at 650C and 850C and at 700C for the PIR in order to achieve steady flaming conditions. Polyurethane foam, when burnt, gives off: Sulfuric acid Cyanide gas Ethane Phosphine. 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. Both authors read and approved the manuscript. These substances can include carbon dioxide, carbon monoxide, formaldehyde, aldehydes, and other volatile organic compounds (VOCs), as well as soot and particulates. The average well-ventilated yield of HCN was found to be 4mgg1, while it was 9mgg1 for under-ventilated conditions. Since 2004, by law, the U.S. requires all mattresses to be fireproof to a specific temperature point and ever since the toxicity levels in foam memory mattresses have increased. 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 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. Avar G, Meier WU, Casselmann H, Achten D (2012) Polymer Science: A Comprehensive Reference, Polymer Science: A Comprehensive Reference, 10, p411-441. Summing these contributions generates a fractional effective dose (FED). (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam.
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