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. 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. In a letter to the editor of the journal, Barbrauskas et al. This suggests that any amines formed would have reacted with isocyanates in the vapour phase to form ureas, some of which would have condensed to produce the observed waxy white substance. 2012). Fire and Materials 5(4):p133–141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. Isocyanates should be considered when assessing the fire toxicity of polyurethane foams, due to their acute irritating effects and chronic effects associated with exposure. 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. In this modification, the controlled atmosphere cone calorimeter (CACC) (Babrauskas et al. The use of 13C labelling by Chambers et al. This results in relatively high yields of CO and HCN during under-ventilated flaming and relatively low yields during well-ventilated flaming. From this, the library of data was sorted into categories of combustion/pyrolysis conditions, material/product, type of test animal and toxicological endpoint. 2. 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). Other fire retardants such as melamine are reported to significantly increase the HCN yield of polyurethane foams. 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. 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. This makes the isocyanate functional group highly reactive towards nucleophiles with an available hydrogen. Polyether polyols are more resistant to hydrolysis, but less stable to oxidation, while for polyester polyols it is the opposite. Chambers et al. In many studies (such as those by Stec and Hull (2011), Purser and Purser (2008a) and Blomqvist et al. Stec and Hull (2011) assessed the fire toxicity of building insulation materials using a steady state tube furnace as described in ISO/TS 19700 (2013). Over short periods, inhaled CO impairs an individuals ability to escape, causing different effects at different concentrations. 2012). 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. This slight decrease is probably within the limits of experimental error, as it does not follow the general trend shown by most materials. The isocyanate precursors used in the production of polyurethane foams usually consist of aromatic diisocyanates such as toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI). They attributed the different decomposition mechanisms to the physical form of the polyurethane foam, rather than to any chemical differences. It can be used for testing samples 100 × 100 mm and up to 50 mm thick, in both the horizontal and vertical orientation. A new study has shown that breathing the chemicals from polyurethane foam can be dangerous. The authors acknowledged that they did not include isocyanates in their calculations. The average well-ventilated yield of HCN was found to be 4 mg g−1, while it was 9 mg g−1 for under-ventilated conditions. The standard specifies four test conditions, but fails to link them to particular fire scenarios. 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). 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). 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. 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. (2003) used a cone calorimeter to assess the yields of amines, aminoisocyanates and isocyanates from the flaming combustion of a flexible polyurethane foam. A "combustion modified high resilience" flexible polyurethane foam (CMHR-PUF) and a polyisocyanurate (PIR) foam were analysed a steady state tube furnace apparatus. More recent studies have supported and expanded upon the aforementioned thermal decomposition mechanisms of polyurethane foams. However, this did not take into consideration the incapacitating effects of the release of irritant gases. The fire toxicity of a material can also be expressed as a material-LC50, which in this case is the specimen mass M of a burning polymeric material which would yield an FED equal to one within a volume of 1 m3. Today, polyurethane foams can be found in cars, mattresses, baby products and just about everywhere. 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. Polyurethane is made when methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) react with polyols. 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. Similarly, Busker et al. 1984a). 2012). We are having a polyurethane insulation applied to our roof. The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. 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. 1981), probably because of increased use of nitrogen-containing synthetic polymers. To date, there have been no reports to our knowledge of toxicity in occupants of polyurethane-insulated homes. At 1000 °C the hydrogen cyanide produced accounted for a range of between 3.8 and 7.3 % by weight. As the availability of oxygen becomes lower in proportion to the amount of fuel, the yields of certain toxic gases will increase. Preliminary calculations suggested that 27 % of the TDI should be recovered as DAT. As polyurethane foams have very low thermal inertia, application of heat or a small flame can be enough to ignite them. Bulky substituents that impinge on the isocyanate group can reduce its reactivity. 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). 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. In air, the resulting decomposition fragments can be oxidised into CO, CO2, H2O and nitrogen oxides at high temperatures. Fire Safety Journal 42:p340–365, 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. 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