Oxygen rooms in hospitals should have entrances from the top and not from the sides.

Abstract

Gases in general are characterized by the ability of their molecules to move freely in any direction. As a result, they show high diffusivity and miscibility. Spectacular experiments demonstrating these properties are found in most general chemistry textbooks. Although gaseous mixtures do not usually settle out in layers, density differences often prevent intermixing of individual gases. A striking example of this is encountered in the famous Dog's Cave (Grotto del Cane) in the volcanic area near Naples, Italy. In this cave carbon dioxide, about 34% heavier than air, pours out from earth fissures in the floor and collects to the height of 2 to 3 ft. (61 to 91 cm. ). No appreciable amount of carbon dioxide diffuses above this level. As a result it is possible for a man to walk into the cave safely, but dogs or other small animals are soon overcome. In the same area after