Assessment of chemical asphyxia caused by toxic gases generated from rigid polyurethane foam (RPUF) fires.

Rigid polyurethane foam (RPUF) is widely used for thermal and sound insulation owing to their low thermal conductivity and light weight. However, they have serious disadvantages, including flammability and toxic gas generation, which can cause chemical asphyxia during a fire. Carbon monoxide (CO) and hydrogen cyanide (HCN) are representative toxic gases formed by incomplete combustion and HCN, in particular, is closely related to polyurethane product fires. In this study, the risk of inhalation of toxic gases such as CO, HCN and NO during RPUF fires was demonstrated convincingly through the analysis of carboxyhemoglobin (COHb), cyanide (CN) and methemoglobin (MetHb) in the postmortem blood samples of 38 victims of RPUF fires. To better understand the toxic gas poisoning and chemical asphyxia, we classified all cases into two groups based on the extent of injuries and location where the victim was found. Mean concentrations of COHb and cyanide in group 1 without injuries were approximately two times higher than in group 2 with severe injuries, while concentrations of free MetHb showing possibility of NO inhalation were approximately six times lower than in group 2. Furthermore, we presumed concentrations of cyanide at the time of death and five cases showed the possibility of cyanide poisoning.