Breathing Gas
Definition
Breathing gas is a specially blended mixture of gases used by divers to breathe underwater at various depths.
More on Breathing Gas
Diving requires breathable gases that provide adequate oxygen while controlling levels of nitrogen and helium. Common breathing gases include air (21% oxygen, 79% nitrogen), nitrox (enriched oxygen), trimix (oxygen, nitrogen, helium), and heliox (oxygen and helium). Different gas blends are used depending on the depth, duration, and objectives of the dive. Gas selection is critical for managing risks like nitrogen narcosis, oxygen toxicity, and decompression sickness. Proper training and gas analysis are required for any blend beyond air.
Frequently Asked Questions
Air contains 21% oxygen, while nitrox is enriched with more oxygen (usually 32% or 36%), reducing nitrogen uptake and extending no-decompression limits.
Helium reduces nitrogen narcosis and oxygen toxicity at great depths. Trimix and heliox are used in technical and commercial diving beyond recreational limits.
Not at depth. Oxygen toxicity becomes dangerous at partial pressures above 1.4 ATA. 100% oxygen is used for shallow decompression stops only.
A gas analyzer measures the oxygen (and sometimes helium) content of a breathing gas mix, ensuring it matches what was planned before the dive.
A nitrox certification teaches gas theory, oxygen exposure limits, and how to analyze and plan dives using EANx blends.