Scuba diving

Some common gases used for scuba tanks

Among us must have seen divers using air-breathing tanks underwater. Unlike other diving methods, relying on breath or breathing under pressure from the surface of the diver usually carries a breathing air source that allows them to move more freely than the hold breath.

So do you know what gas they carry with you?

Scuba diving tanks are metal tanks that are compressed with natural outdoor air inside, not oxygen. Used to provide gas for you to breathe in the water for a safe time. There are valves for opening and closing.

Scuba Cylinder Care — O2ToGo Dive Centre

There are many other types of tank capacity available, depending on the size and pressure resistance of the tank. The volume of the bottle is measured in liters or kilograms. By compressing the air, a small bottle can hold a very large amount of air. There are 3 common sizes: 8, 10, 12 liters. In some diving cases it is necessary to combine 2 tanks to get more diving gas for longer. The pressure of the gas diving tank can withstand higher than about Mpa (320 bar). Typical pressure is 20.7, 27.6 (207 – 276 bar).

Some common breathing gases:


A mixture of oxygen, nitrogen and helium gas and is often used in deep diving in engineering and commercial diving instead of air to reduce nitrogen toxicity and to avoid the risk of oxygen poisoning.


It is a mixture of Oxygen and helium gas and is often used in very deep diving to eliminate nitrogen poisoning.


A form of trimix that is blended from helium and air without mixing with pure oxygen. It always has a ratio of 21 oxygen and 79 nitrogen. The balance of the mixture is helium.


A mixture of oxygen, helium, and hydrogen and is used to dive below 130 meters.


A mixture of hydrogen and oxygen gas, used as a breathing gas for very deep diving.

Fun Diving - Cham Island Diving Center Hoi An, Vietnam

Some common gases used for scuba tanks:


A mixture of 21% oxygen, 78% nitrogen, and about 1% other gases, mainly argon. To simplify these calculations the last 1% is usually treated as if it were nitrogen. It is the most popular diving gas. Due to its nitrogen content causes nitrogen toxicity. It was only used to dive up to 40 meters (130 feet) deep.

Pure oxygen:

Mainly used for acceleration of military, commercial or technical diving and is only safe to a depth of 6 meters (maximum operating depth). Through this depth, it is susceptible to oxygen poisoning.


A mixture of oxygen and air, and generally mixtures with more than 21% oxygen. It can be used as a tool to speed up decompression nodes in water or reduce the risk of decompression disease and thus prolong diving time.

Helium is present in most gas mixtures used in scuba tanks. Thereby, we can see the importance of helium how. In addition to gas for helium scuba diving, there are other uses and applications for other fields such as medicine, welding, cold electronics, …