It was called "Respirable air".
"Our Legal Heritage"
S. A. Reilly
There one finds the Respirable air, the illuminating light, normal heat, classic cookery, and, in moderation, so many other things without which it would not be worth the while to promenade this round ball.
"The Simple Life"
Charles Wagner
To each elemental being the element in which it lives is transparent, invisible, and Respirable, as the atmosphere is to ourselves.
"The Best Psychic Stories"
Various