Helium-Air

The production of helium, a light, rare gas, has already become a prime requisite for aviation because it is non-inflammable and saves dirigibles from fire hazard. A new use for it is likely to be developed as the result of researches by the Department of the Interior.

Ordinary air is composed of four-fifths nitrogen and one-fifth oxygen and smaller amounts of other gases such as carbon dioxide. The oxygen content of air is the only part valuable to man in breathing. When men work in certain types of caissons, in diving suits or diving bells, they are subject to great air pressure. Under these circumstances, nitrogen goes into the tissues of the body. When the external pressure is released, as by coming out of a caisson or being raised to the surface of the water, the excess nitrogen in human tissues tends to form bubbles. If one of these occurs in the spinal cord or brain it may cause paralysis or death. If they form in the right half of the heart they are forced into the lungs where they form a frothy mixture, interfering with circulation and breathing. These effects give rise to what is known as compressed air illness or caisson disease.

Effort is made to avoid these ill effects by having men who work under heavy air pressure gradually removed from it; but ever and again, through accident or carelessness, it occurs.

The experimenters of the Department of the Interior, according to their claim, have found that, by mixing helium instead of nitrogen with oxygen, a breathing mixture is formed equally as good as ordinary air, and the helium has not the tendency to "bubble" and cause the disease when the pressure is released.

Experiments with animals, partially confirmed by experiments with men, showed that the time of gradual decompression with helium-oxygen mixtures can be reduced even to one-sixth of that required with ordinary air without evil effects. If so, the use of helium-air will greatly increase the margin of safety for workers in compressed atmospheres.