The lowest temperature at which a liquid will give off vapors at a sufficient rate to support a momentary flame across its surface is known as its: . In a report from the same laboratory, Braun et al. The test conditions were designed so that the fire conditions met the ISO 19706 (2007) fire type 2 (well-ventilated flaming fire <0.75) and fire type 3b (post-flashover fire in large or open compartments ~2.0). Oxygen depletion can be lethal if the oxygen concentration falls below tenable levels (~6%). 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). (2007)), the sample is raised to a fixed furnace temperature, which is further increased in the gas phase during flaming combustion. 4). 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). Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. The samples tested included both commercial rigid polyurethane foam and polyisocyanurate foam. Fire Safety Science - Proceedings of the First International Symposium, p1111-1122, Markets and Markets report (2011) Methylene Diphenyl Diisocyanate (MDI), Toluene Diisocyanate (TDI) and Polyurethane Market (2011 2016): Markets and Markets CH 1596, July 2011, Marsh ND, Gann RG (2013) Smoke Component Yields from Bench-Scale Fire Tests: 4. 2 (Avar et al. UPDATED 8/16/2011 The Massachusetts Division of Fire Safety (DFS) is investigating the causes of three house fires that were ignited while insulation contractors were installing spray polyurethane foam. Spray foam can potentially generate toxic emissions under these circumstances. Polyurethane and other organic foam materials are finding increased use on vessels because of their excellent insulating properties and light weight. However, due to the poor reproducibility of smoke chamber experiments, the tendency for it to give very low HCN yields, and the fact that the experiment is well-ventilated, the reported toxicity is likely much lower than in a real fire situation. It forces combustion by driving the sample into a furnace of increasing heat flux at a fixed rate, so that, by running several tests with the same material with different ventilation conditions, each fire stage can be replicated by steady state burning. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. 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. Both of the materials showed a clear relationship with the HCN yield increasing with . The authors made this assertion based on the yield of average CO from post-flashover fires being 2009mgg1. As the main reactive group that isocyanates react with, polyols are a major component of the resulting polyurethane product. 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. Only the SSTF has a heated reaction zone which replicates the hot layer. 1982), a developmental method (SwRI/NIST method) which used a radiant heater on the sample which lead into a 200 L exposure chamber, a cone calorimeter (ISO 5660 2002), a furniture calorimeter (as described in Babrauskas et al. 2008; Kaplan 1987b). The authors noted a primary depolymerisation of the foam which would release volatile TDI and leave the polyol precursors in the condensed phase. The main toxic combustion products can be divided into two classes: asphyxiant gases, which prevent oxygen uptake by cells, with loss of consciousness and ultimately death; and irritant gases which cause immediate incapacitation, mainly by effects on the eyes and upper respiratory tract, and longer term damage deeper in the lung. The trimerisation results in a highly stable isocyanurate ring which confer additional thermalstability to polyisocyanurates (Scheme7). The cribs used in the ISO 9705 tests were constructed from PIR sticks which burned rapidly, albeit with minimal damage to the room. The products generated in the flame zone then pass through the heated furnace tube, maintaining a high temperature, as in the upper layer of a compartment fire. Fire Safety Science Proceedings of the ninth international symposium. Garrido and Font (2015) reported two main steps in the inert-atmosphere decomposition of flexible polyurethane foams. It is inexpensive and easy to install, however, it is a severe fire risk and requires a thermal barrier to make it safe. FEC model from ISO 13571. Journal of Applied Polymer Science 111:p11151143, Stec AA, Hull TR (2011) Assessment of the fire toxicity of building insulation materials. 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. Recent work by Allan et al. These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. 6). 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. As the availability of oxygen becomes lower in proportion to the amount of fuel, the yields of certain toxic gases will increase. Isocyanurate rings are the most thermally stable in an inert atmosphere and decompose between 270 and 300C. As fires grow, they become ventilation controlled, and fires in enclosures such as buildings rapidly change from well-ventilated to under-ventilated. 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 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). This char can decompose further, leaving behind a residue at >800C, to produce simple organic fragments and some polycyclic aromatic hydrocarbons (PAHs). Do memory foam mattresses give off toxic fumes? The applied heat flux must be large enough for burning to continue at oxygen concentrations as low as 5%. At high concentrations these acids can cause pulmonary oedema and death (Paul et al. The two main families of polyols used are polyether polyols and polyester polyols (Fig. Urethane Foam Health Effects | livestrong Michal (1982) reported a similar trend at a fixed air flow rate. Hexamethylene diisocyanate (HDI) (i), 1,5-naphthalene diisocyanate (NDI) (ii) and isophorone diisocyanate (IPDI) (iii). Diesel engines use the principle of _____ to ignite fuel vapor. As a result of this, studies that use ventilation controlled conditions, such as those using the steady state tube furnace (ISO/TS 19700 2013), are more likely to give a realistic representation of these reduced oxygen environment fire conditions. When a liquid fuel gives off enough vapors so that it can be . Bott et al. Secondary air is added in a mixing chamber to give a total gas flow of 50Lmin1. Heating of polyurethane foam while working on pipes Heating MDI-based glues Soldering Treatment with a heat gun Cutting with torches or hot wire Hot scissors Grinding Sawing It has been estimated that non-flaming thermal degradation of some polyurethane products may begin as low as about 150C (300F) to . Further reactions occur with amines, water, ureas, urethanes and even other isocyanates to produce a diverse range of functional groups including urethanes, ureas, isocyanurates, carbodiimides and uretdiones. 9). New memory foam smell? 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. The review refers to a publication by Babrauskas et al. In many studies (such as those by Stec and Hull (2011), Purser and Purser (2008a) and Blomqvist et al. 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. DiNenno) Fourth Edition. 12, feeds the sample (typically around 25g of pellets or granules) into its hot zone at a fixed rate, under a controlled air supply, inside a horizontal silica tube of diameter 48mm, allowing adequate mixing of fuel and oxidant. The rigid polyurethane foam yielded ~55mgg1 CO and ~0.5mgg1 of HCN. Nitric oxide (NO) and nitrogen dioxide (NO2) are non-flammable gases present in fire effluents. 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. Fire Safety Journal 42:p340365, ISO 12136 (2011) Reaction to fire tests Measurement of material properties using a fire propagation apparatus, ISO 13344 (1996) Estimation of lethal toxic potency of fire effluents, ISO 13571 (2012) Life-threatening components of fire-Guidelines for the estimation of time available for escape using fire data. In: Fahima Z, Eram S (eds), InTech. McKenna, S.T., Hull, T.R. 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. California Privacy Statement, Most rigid foams and speciality polyurethanes use polymeric MDI derivatives which are mixtures components such as dimers and trimers (Fig. Comparison with Room Fire Results, NIST Technical Note 1763, National Institute of Standards and Technology, Gaithersburg, MD, Michal J (1982) Determination of Hydrogen Cyanide in Thermal Degradation Products of Polymeric Materials. Preliminary calculations suggested that 27% of the TDI should be recovered as DAT. In general conversion efficiencies are high for halogen acid gases. Anderson RC, Croce PA, Feeley FG, Sakura JD (1983) Study to assess the feasibility of incorporating combustion toxicity requirements into building materials and furnishing codes of New York State: Final report, vol I, II, III, Arthur D. Little, Inc. Report, Reference 88712, May 1983. (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. 2012). The study also suggested that any remaining isocyanates residue would react with themselves to produce polycarbodiimides, thus anchoring the isocyanate precursors in the condensed phase until around 600C, where they would fragment. Springer Nature. Isocyanates also react with themselves in various ways to produce dimers, trimers and completely new functional groups. The difficulty of replicating the conditions of fully developed under-ventilated flaming on a bench-scale is caused by several practical problems. Summing these contributions generates a fractional effective dose (FED). They produce a strong odor for awhile after manufacture. 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. Polymer Degradation and Stability 98:535541, Anderson RA, Watson AA, Harland WA (1981) Fire Deaths in the Glasgow Area: I General Considerations and Pathology. 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). (2006) and also Garrido and Font (2015). PML 1998-A97. At high concentrations nitric oxide is rapidly oxidised in air to form nitrogen dioxide, however, at the concentrations found in fire gases, most of the nitric oxide remains unoxidised. 13) (UK Fire Statistics 2013). 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. 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. However, no amines were detected in the vapour phase. 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.
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