Air Tec divers often use ordinary air (21% oxygen, 79% nitrogen) to depths as deep as 165 feet (in ideal, non-overhead conditions). They sometimes use it as a decompression gas, though not commonly.

EANx Enriched Air Nitrox is an oxygen/nitrogen gas blend with more than 21% oxygen. Tec divers may use EANx to reduce decompression time on long, shallow dives (especially cave dives), or switch from another gas to EANx during ascent to speed up decompression. EANx with 32%, 36%, 50% and 70% oxygen are common tec-diving choices.

Trimix Trimix is oxygen, helium and nitrogen, used for diving deeper than 165 feet, deeper than 130 feet in an overhead environment or even at shallower depths when required by challenging conditions. The addition of helium reduces narcosis at depth and also dilutes the oxygen (oxygen is toxic at high pressures).

Oxygen Tec divers use pure oxygen to accelerate decompression. Because of oxygen toxicity concerns, they cannot use it deeper than 20 feet. However, since the longest stops are the shallowest stops, oxygen markedly reduces overall decompression time.

Argon Tec divers use this, but they don't breathe it! Rather, they use argon to inflate their drysuits because it has superior insulating qualities compared to air.