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APPENDIX A SURVIVAL SUBSYSTEM Two life support systems are required for the proposed coal mine rescue and survival system: a lightweight individual emer- gency breathing device that can be carried continuously by a coal miner and a life support system capable of supporting 15 men for up to two weeks for a small refuge chamber. Emergency Breathing Device The present emergency breathing device for individual miners is the self-rescuer. This device uses the catalyst hopcalite to con- vert carbon monoxide to carbon dioxide as the mine atmosphere is breathed through the self-rescuer. The name hopcalite refers to various mixtures of the oxides of manganese, copper, cobalt, and silver. In "four-component hopcalite" all of these oxides are pres- ent, and the catalyst is precipitated as hydrous oxide. In the two- component catalyst only oxides of manganese and copper are present; the copper is precipitated as a carbonate. Both of these hopcalite catalysts are very effective for low-temperature oxidation of carbon monoxide, although the four-component catalyst rapidly loses its activity at elevated temperatures. Hopcalite is relatively immune to the effects of water vapor at elevated temperatures, but at lower temperatures the catalyst must be protected from water vapor by the addition of a drying agent. It must also be protected from organic materials that can poison the catalyst. In a 1 1/2 percent carbon monoxide atmosphere, temperatures at the mouthpiece of the self-rescuer may reach 185°F because of the exothermic reaction of the conversion of carbon monoxide in the catalyst. At concentrations higher than about 11/2 percent, the temperature of the inhaled air becomes greater than can be tolerated by the man wearing the self-rescuer. In addition to the disadvantage of the high temperature of the inhaled air, the percentage of carbon dioxide in the air breathed by the wearer is increased by three factors. First, following a mine fire or explosion, the concentration of carbon dioxide in the air is substantially increased. Second, the carbon monoxide is converted to an equal percentage of carbon dioxide by the action of the self-rescuer. - 15 -
