Ventilation of impermeable clothing: the effectiveness of the ambient atmosphere in ventilating coveralls worn in hot and humid conditions.

In the handling of highly concentrated liquids used as oxidants in guided weapons or for protection against highly toxic gases and liquids the Services require a completely impermeable coverall which can be worn for periods of up to two hours. It is well known that wearing such clothing restricts evaporative cooling and may cause collapse from heat stroke. Robinson and Belding (1948) place a limit of one hour at 750 F. and 25 minutes at 850 F. on the time of wearing such a suit. Under tropical and desert conditions the problem of cooling is particularly difficult and some form of ventilation becomes essential. Since the beginning of the century patents have been issued for devices to relieve this heat stress by circulating cooled air under clothing. None of these devices, however, is practicable for use under Service conditions in remote areas nor do they meet a requirement that the protective clothing should be self-contained, i.e., it must not be attached to a remote source for cooling or dehumidifying. It seemed, therefore, that any practical method of ventilation would necessarily be based on the use of ambient atmospheres, but no information was available about this. Although such a method cannot maintain temperature equilibrium in a wearer, except under mild conditions, it was felt desirable to ascertain the degree of alleviation which might be obtained under various conditions. To this end a study has been made of the physiological strain produced in men performing light work in a range of simulated climatic conditions while wearing impervious suits through which ambient air was pumped at controlled rates. A practical garment would need a portable pump to supply the air, and the present data will be used in the development of a suitable pump. Experimental Subjects.-Nine fit young men of ages ranging from 18 to 25 years volunteered for the trials. Two were Naval ratings, six were men from these laboratories, and one was an Army officer from the Weapons Research Establishment, Woomera. Seven were used in each trial, five as subjects and the other two as controls.