[Hygienic control of contingencies associated with local fire events aboard piloted orbital stations]

Based on the multiyear experience of hygienic control of the orbital stations, there are three causes of contingent air pollution: leakage of service system pipeline with chemical working bodies, spills of reagents used in biochemical and technological experiments, and air pollution by products of thermal oxidative degradation of nonmetallic materials. The authors describe their experience in successful elimination and prevention of hazardous consequences of fire aboard the space stations. Analysis of air pollution dynamics after actual fire events in the space station modules showed that it approximates a two-chamber air flow model with two phases of pollutant equilibration: first a rapid fall of concentration in the module on fire till air in the modules gets completely mixed, and then slow elimination of harmful pollutant from air. Identified were markers,--propylene and methylmetacrilate,--reacting to first signs of fire. Carbonic acid nitriles were recognized as toxic products of destruction. The positive effect of intermodular ventilation on dilution of toxic products of thermal oxidative destruction of materials was demonstrated. Satisfactory agreement of calculated and factual pollutant concentrations on board Mir permitted conclusion on applicability of the theoretical model to prediction of levels of air pollution due to contingency.