Divers use a gas mixture of Helium and Oxygen ("Heliox") instead of ordinary compressed air at diving depths greater than one-hundred (100) feet, to prevent Nitrogen Narcosis, or "Rapture of the Deep". The decompression chamber has to pressurize the diver to the same or greater depth than the maximum depth he reached on the dive, to force the gas bubbles in his blood back into solution, so if the chamber pressure is greater than 100 feet, Heliox must be used in the chamber as well. The Helium in the gas mixture causes the classic high-pitched voices caused by Helium inhalation for everyone inside the chamber.