FIRE SAFETY, SMOKE TOXICITY AND ACIDITY

The question of the importance of smoke toxicity in relation to fire hazard or to the emission of acid gases in smoke is misdirected. Although roughly 2/3 of fire victims die as a direct effect of smoke toxicity, it is extremely rare that their deaths are caused by the inhalation of smoke from a specific very toxic material. In fact, probably well over 90 % of fire deaths are the result of fires becoming too big (often so big that they extend beyond the room of origin) and thus resulting in too much toxic smoke. There is excellent correlation between blood CO concentrations in fire victims and the resulting fire fatalities; thus the toxic effects of other combustion products are negligible. More important than any individual combustion product is the fact that if a fire remains small it almost never causes fatalities. Therefore, fire hazard is directly related to the fire heat release rate (i.e. the fire intensity) with other issues (such as smoke toxicity) being of minor relevance. The toxic potency of the smoke of almost all individual polymers lies within a very small band, so that they are almost indistinguishable. At flashover, every polymer will give off ca. 20 % of its weight as CO: that is toxic enough to be lethal. The lethal toxic potencies of CO and HCl are similar and significantly lower than that of acrolein or HCN. In order to study the small toxic effects that can be added to the major heat release effect, th