Show k I 1 OXYGEN AND AIR IN SAFETY normal air contains about 21 percent per cent of c oxygen man works best at this proportion of oxygen A candle ori or oil flame will not burn in atmospheres containing less than ihan ap proximately I 1 az 16 percent percent oxygen yet man is sufficiently adaptable tp to get along fairly well in 1 7 per cent of oxygen he will breathe a little faster and a little deeper the effect is about the same as going from pittsburgh to ito denver colorado with elevations of to feet respect respectively biely but most men can not work in air with oxygen below 13 per cent the point where an acetylene flame is ext extinguished by oxygen deficiency no one should ever enter an atmosphere where an acetylene flame goes out without an oxygen breathing apparatus or an air hose mask in an atmosphere containing between 10 and 13 per cent oxygen men become dizzy pant have a rapid heart beat and often suffer from headache ato 10 per cent usually produces unconscious unconsciousness ne and ultimately death according to a bureau of mines circular ap f a |