A scuba tank is also known as a diving cylinder. It houses and transports breathable compressed air as part of a SCUBA (Self-Contained Underwater Breathing Apparatus). Scuba tanks provide gas to the diver through diving regulators. Scuba tanks are usually filled to either the 232 or 300 bar, with volumes of three to 18 liters or with a gas carry capacity of 850 to 4200 liters. Tanks that come in 1.5 and two liters are also available, though these types are not usually used for breathing, but rather for buoyancy control devices and suits that require inflation.
The term diving cylinder is used by professional people as a technical term, whereas scuba tank and diving tank are used more often by non-professionals and are non-technical terms.
Purpose of the Scuba Tank
The purpose of diving tanks may differ depending on the nature of the dive. If the water is warm and visibility is good, divers usually carry just one scuba tank. Coral reef diving and other recreational diving does not require divers to go very deep. As a result, the need for more than one scuba tank is not necessary. However, when diving in cold water with low visibility, it is advisable for divers to bring more than one scuba tank. In the northern part of Europe where the water is very cold and visibility is low, divers bring at least two scuba tanks for emergency purposes.
Besides the two diving cylinders there is another one used for emergency purposes. A pony bottle is a very compact tank used for backup air supply. It ranges from 1.7 cubic foot to 40 cubic foot depending on the situation and conditions.