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. More recent studies have supported and expanded upon the aforementioned thermal decomposition mechanisms of polyurethane foams. Fire Sci Rev 5, 3 (2016). Prog Energy Combust Sci 21:197237, Purser DA (2002) Toxicity Assessment of Combustion Products, The SPFE Handbook of Fire Protection Engineering 3rd Edition, Edited by DiNenno, P.J. Ask Pablo: How Bad Is Memory Foam? Google Scholar, Allan D, Daly J, Liggat JJ (2013) Thermal volatilisation analysis of TDI-based flexible polyurethane foam. 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. (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam. Springer Nature. The yield of CO had a wide range during the under-ventilated tests due to inconsistent flaming of the sample with yields from 100250mgg1. 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. In the case of flaming combustion, one of the most important factors relating to the toxic product yield is the fuel/air ratio which, as defined earlier, can be expressed as an equivalence ratio (). 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). In contrast to the relativelywell-defined effects of asphyxiants, the effects of exposure to irritants are more complex. Both types of foam yielded very similar products at temperatures above 600C. 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. NIST performed the experimental burn tests 1 on 4-inch (10-cm) thick by 4 ft x 4 ft (1.2 m x 1.2 m) wide polyurethane foam slabs. PDF Fire Properties of Polyvinyl Chloride 2012). Most fuel nitrogen is released as N2, but in well-ventilated combustion conditions a proportion is released as oxides of nitrogen (mainly NO) and in under-ventilated combustion conditions a proportion is released as HCN (Purser & Purser 2008a). The interior of large flames are always under-ventilated, because oxygen cannot penetrate the flame. The process of . Work by Guo et al. 8 and Table3. Two mechanisms have been identified for the toxic effects of cyanide. Primarily, isocyanates react with alcohols to produce urethane linkages in the polymer (Scheme1). 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. 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. 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. For any larger fire there will always be a significant yield of CO, HCN (from nitrogen containing materials), hydrocarbons and smoke. Table1 shows the relative reactivity of isocyanates with nucleophiles at 25C without the presence of a catalyst. Top of Page. (2006) and also Garrido and Font (2015). The authors declare that they have no competing interests. In order to relate the fire effluent toxicity to a "maximum permissible loading", the FED can be related to the mass of material in a unit volume which would cause 50% lethality for a given fire condition. volume5, Articlenumber:3 (2016) Respiratory Issues First, polyurethane is a petrochemical resin that contains known . Fire and Materials 5(4):p133141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. This is due to the large range of available fire retardants found in polyurethane foams, which suggests that the toxicity will likely follow the general trends in the literature for all materials regarding fire retardants. The difficulty of replicating the conditions of fully developed under-ventilated flaming on a bench-scale is caused by several practical problems. 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. Bench-scale methods used for generating toxic effluents from polyurethane foams have met with controversy. 4)). The polyurethanes used were elastomers based on TDI, which could potentially have differing decomposition mechanisms to their foam counterparts. Biurets are the result of the reaction of isocyanates with substituted-urea functional groups and allophanates are formed in small amounts (unless catalysed) by the reaction of isocyanates with urethanes. Therefore, in certain conditions, polyurethanes foams can reach their auto-ignition temperature and ignite which will significantlyalter the effect the decomposition mechanisms and resulting products. But many products or materials continue off-gassing even after the "new smell" has gone awaythe fumes are just much more subtle. Fire and Materials 31:p327354, Schnipper L, Smith-Hansen ES (1995) Reduced combustion efficiency of chlorinated compounds, resulting in higher yields of carbon monoxide. A detailed understanding of the thermal decomposition chemistry of polyurethane foams is necessary in order to relate the toxicants generated during bothflamingand non-flaming combustion of the polymer to its structure. PDF Polyurethanes and Thermal Degradation Guidance The reported yields were extremely low for both CO and HCN, as the NBS smoke chamber apparatus is a well-ventilated fire scenario reported to give low HCN yields (Table6). The authors would like to thank Dr. Linda Bengtstrom for her contribution regarding the toxicity of isocyanates. A review by Paabo and Levin (1987) found that there is no difference in the decomposition products of rigid and flexible polyurethane foams at high temperatures regardless of their differing degradation mechanisms at lower temperatures. Fire and Materials 11:p129, Paul KT, Hull TR, Lebek K, Stec AA (2008) Fire smoke toxicity: The effect of nitrogen oxides. Critical Reviews in Toxicology 32(4):259, Article . Refer to MSDS. Most rigid foams and speciality polyurethanes use polymeric MDI derivatives which are mixtures components such as dimers and trimers (Fig. By using this website, you agree to our Med Sci Law 21:60. 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. Equation Polyurethane foam may be formed at a construction site or installed in the form of board stock (see the "Composite Insulations, Structural Insulated Panels" section). 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. 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 full-scale test showed good accordance with the SSTF data considering the inherent unreliability of large-scale testing. 6 Sources of Toxic Chemicals (VOCs) in Your Home Polymer Degradation and Stability 93:p20582065, Tewarson A (2002) SFPE Handbook of Fire Protection Engineering, 3rd ed. Polyurethane. Syntheticpolymeric materials may be divided into thermoplastics and thermosets. Although these temperatures can provide a good general idea of which bonds will be likely to break down with heating, the steric and electronic effects of the attached groups can affect the strength of the bonds and thus the temperature at which the bond will decompose. International Association for Fire Safety Science, Ravey M, Pearce EM (1997) Flexible Polyurethane foam. 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. Faster. 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. This value decreased to 18mgg1 at ~2.0. The peak HCN value reached was 10mg per g1 in the under-ventilated tests. ISO 19706 (2011) Guidelines for assessing the fire threat to people. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. Hazwoper lesson 3 Toxicology Flashcards | Quizlet The fire department was not immediately called, so the oil burned completely. Acrolein and formaldehyde are formed especially from cellulosic materials under non-flaming decomposition conditions, but products of vitiated combustion contain other organic irritants. DiNenno et al., eds.). (PDF) The fire toxicity of polyurethane foams - ResearchGate Fire and Polymers II: Materials and Tests for Hazard Prevention 599:p498517, Chun BH, Li X, Im EJ, Lee KH, Kim SH (2007) Comparison of Pyrolysis Kinetics between Rigid and Flexible Polyurethanes. 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. However, many people fail to escape from fires because of the incapacitating effect of smoke (obscuring visibility) and its irritant components which cause pain, preventing breathing and escape or reason death occurred. Equations2 and 3 have been taken from ISO 13571 (2007). The flexible foam produced ~175mgg1 of CO and 5mgg1 of HCN. The first step is the decomposition of the urethane bonds to release and volatilise isocyanates up to 300C, with long chain alcohols being left behind in the condensed phase, followed by the alcohols degrading at around 400C. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. DiNenno et al. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. Gaithersberg, MD, Babrauskas V, Twilley WH, Janssens M, Yusa S (1992) Cone calorimeter for controlled-atmosphere studies. 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). The authors suggested that the presence of oxygen does not affect the mechanisms by which CO and HCN are produced. ISO/TS 19700 (2013) Controlled equivalence ratio method for the determination of hazardous components of fire effluents the steady state tube furnace. 1982), and a three-compartment large scale test. Foam: Fire Hazard and Fire Barrier | Monolithic.org 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. These reactions make up the basis of polyurethane chemistry and can be used to tailor polyurethanes with a range of properties by varying the structure and ratios of the individual components. A polyether polyol (i) and a polyester polyol (ii). al, 2014). (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. The authors acknowledged the complexity of the decomposition of the material but were able to summarise it effectively in a 5-step mechanism (Fig. 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. Paabo and Levin (1987) reviewed the literature of the toxic product generated by the combustion of rigid polyurethane foams. Investigations by Woolley et al. 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). 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. A large number of studies have been performed over the last 50years 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. 1982), the authors exposed male Fisher 344 rats in a 200L exposure chamber to the fire effluent from the flaming and non-flaming combustion of both materials. 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. Ask if the mattress materials are generally free of VOC and HAPs. 6). In general conversion efficiencies are high for halogen acid gases. The polyurethane market was estimated to be worth $33 billion in 2010 and is expected to continue to grow to over $55 billion by 2016. 5-step decomposition mechanism for flexible polyurethane foam (Rogaume et al. Isocyanates also react with themselves in various ways to produce dimers, trimers and completely new functional groups. McKenna, S.T., Hull, T.R. TDI is produced as the 2,4- and the 2,6- isomer which have a boiling point of 121C and 120C respectively. They produce a strong odor for awhile after manufacture. In the smoke chamber, the highest reported yield during flaming combustion was 1.02mgg1. CO and HCN are the main asphyxiants produced during the combustion of polyurethanes and there have been a large number of studies published regarding their yields. The polyester based polyurethane began to decompose at 284C with a secondary decomposition step at 359C. The heating of polyurethanes in an inert-atmosphere results in the progressive rupturing of bonds as a function of temperature. The yields of CO and HCN at varying and temperature are presented in Table5. Purser model, [AGI] is the concentration of inorganicacid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2]0.05. 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. 3 Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. . to FED. Free of VOCs and HAPs. 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? Other fire retardants such as melamine are reported to significantly increase the HCN yield of polyurethane foams. (2011) developed a mechanism based on both condensed and gas-phase decomposition in air. (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. The findings from these studies demonstrated that yields of different toxic products are highly dependent on equivalence ratio (either positively or negatively correlated), and elemental and molecular composition of the material. The results of these experiments and the mechanism of decomposition derived correlated well with work by Rein et al. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. Building renovations, demolition, or building disassembly done years later can disturb spray foam insulation. 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. 1986). 50 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. At ~2.0 the CMHR-FPUR resulted in 8% and 11% nitrogen recovered as HCN for 650C and 850C respectively. 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. The detection of the amino MDI derivative in the tar further supports the literature reports of a secondary decomposition mechanism where isocyanates trapped in the condensed phase are converted irreversibly into their amine derivatives. Polyol fragments in the gas phase will also begin to decompose at >800C to produce simple organic fragments and PAHs. PDF CORE - Aggregating the world's open access research papers As the availability of oxygen becomes lower in proportion to the amount of fuel, the yields of certain toxic gases will increase. The resulting substituted urea can then react with another isocyanate to pro-duce a biuret linkage (Scheme 4). The Model Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. 10. Provided by the Springer Nature SharedIt content-sharing initiative. The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. p 1-30. 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. 2 More recent work by Shufen et al. The fire toxicity of polyurethane foams. In general, isocyanate (R-NCO) exposure causes irritation to the skin, mucous membranes, eyes and respiratory tract (NIOSH 1989). Fumes Tiny particles are produced from heating, volatilization, and condensation of metals (examples: zinc oxide fumes from welding of galvanized metal). (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. 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). Reliable rate of heat release, fire effluent toxicity and smoke generation data are all essential components of such an assessment. Fire Safety Journal 40:439465, Aneja A (2002) Chapter 2, Structureproperty Relationships of Flexible Polyurethane Foams, PhD. Appropriate formulation affords a degree of control over the cross-linking in the polymer without the need for additional cross-linking agents. Most fire deaths and injuries actually occur in residential fires, although assessment of fire toxicity is currently focused on areas where escape is restricted, such as aeroplanes, railway carriages, and passenger ships, which include requirements to quantify the fire toxicity of internal components. 11) ultimately giving well-ventilated flaming. The authors also noted that the presence of aldehydes was detected during the flaming combustion of the flexible foam, albeit in extremely low yields. The yields of some of the most toxic gases from unwanted fires (such as CO, HCN and some organic irritants) have been demonstrated to be directly related to the combustion conditions (Purser 2002). Is Memory Foam Toxic? | Sleep Foundation This is due to the concentration of oxygen directly under a flame being close or equal to 0% (Schartel & Hull 2007). 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). Equation 3 calculatesthe Fractional Effective Concentration (FEC) of sensory irritants in the fire effluent which limit escape. Rigid polyurethanes primarily produced aromatic compounds in the condensed phase products of decomposition, whereas flexible polyurethanes produced aromatics, alcohols, aldehydes and heterocycles. Do memory foam mattresses give off toxic fumes? Sub-ambient differential distillation of the remaining residue yielded a range of short-chain aldehydes (such as formaldehyde and acetaldehyde), ketones, alkenes and high molar mass polyol fragments. The 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. 1992), shown in Fig. 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. Brit Polym J 1:p203204, Braun E, Gann RG, Levin BC, Paabo M (1990) Combustion product toxic potency measurements: comparison of a small scale test and real-world fires. Terms and Conditions, However, spray foam insulation is a highly energy-efficient product and quickly offsets its manufacturing footprint. Polyurethane Fume Exposure And Your Health: What You Need To Know In general, How do low-density materials (such as polyurethane foam) burn compared to higher-density materials (cotton padding) of similar makeup? NO. 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. For example, Levin and coworkers reported that melamine-treated flexible polyurethane foam generated 6 times more HCN than an equal amount of non-melamine treated foam. Most polyurethanes are cross-linked to some degree and decompose without melting. 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. 2013). These substances can include carbon dioxide, carbon monoxide, formaldehyde, aldehydes, and other volatile organic compounds (VOCs), as well as soot and particulates. During these tests, the PIR was set up as wall panels covered on two faces with aluminium foil. 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. The smoke density chamber (ISO 5659-2) showing a sampling probe for fire smoke toxicity. Does the foam give off toxic fumes if burned? Experimental data reported a 28% recovery of DAT which supports the proposed decomposition mechanism. However, in the field of combustion toxicity testing, this under-ventilated burning is the most difficult to create using bench-scale apparatus.