Emissions from Fires Consequences for Human Safety and the Environment

Sammanfattning: Accidental fires represent a risk for people from the heat and fire effluents produced. It is clear from fire statistics that it is, in fact, the toxic gases that kill and injure many fire victims. Further, there are a number of compounds that are readily produced in fires, which have important sublethal effects on humans. Some of those compounds are known to have a long-term effect on people, and fires might significantly contribute to the emission of such compounds to the environment.

Although, the importance of the quality of the fire effluents has been acknowledged for a long time in the fire science community, information on the detailed composition is to some degree missing. In particular, there has been a lack of real-scale fire experiments including detailed chemical analysis, to confirming the present knowledge-base, which in many cases relies on data from small-scale experiments.

The work presented in this thesis is largely based on the results of a number of unique series of large-scale fire experiments, where the composition of the fire effluents has been characterised in detail. The analyses have included many types of species, e.g.: narcotic fire gases such as CO and HCN, irritants such as HF, HCl and isocyanates, carcinogenic compounds such as benzene, PAHs and dioxins. The particulate phase of the fire effluents has also been characterised in a number of tests.

Information on the production of toxic gases, such as HCN, is important for estimating the time for evacuation in case of fires in buildings. Quantitative information on HCN, and other toxic gases relevant for an evacuation scenario, has been determined in real-scale fire experiments. An application of an FED model for asphyxiant gases, showed that these gases presented the greatest danger in a series of experimental tunnel fires, and that HCN, in particular, had a major impact in these fires.

Further, a chemical kinetic model included in a computational fluid dynamic (CFD) study, has been evaluated for the prediction of HCN production in fires. The prediction of the model was satisfactory compared to the results of large-scale enclosure tests.

An estimate of the total amounts of dioxin, PAH and VOC from fires in Sweden during a specific year was made, by combining the amounts of materials involved in fires with emission factors for these fires. It was concluded that the emissions of PAH, VOC and dioxins from fires are large. The fire related emissions of PAH and dioxins were further shown to be significant and comparable to those from many other sources. For dioxins it is further clear that large catastrophic fires can lead to major emissions.