A diving cylinder, scuba tank or diving tank is a gas cylinder used to store and transport the high pressure breathing air needed for diving. Cylinders provide air to the diver through the regulator.
Diving cylinders are usually manufactured from aluminium or steel alloys, and are normally fitted with one of two common types of cylinder valve for filling and connection to the regulator.
Cylinders used for scuba typically have an internal volume of between 3 and 18 litres and a maximum pressure rating from 184 to 300 bars (2,670 to 4,350 psi). Cylinders are also available in smaller sizes, such as 0.5, 1.5 and 2 litres, however these are often used for purposes such as inflation of surface marker buoys, drysuits and buoyancy compensators rather than breathing.
Choosing a cylinder depends on the length of dive you want to complete, the longer the dive the larger the tank needed. Diving cylinders are most commonly filled with air, but because the main components of air can cause problems when breathed underwater at higher ambient pressure, divers may choose to breathe from cylinders filled with mixtures of gases other than air.
Periodic inspection and testing of cylinders is often obligatory to ensure the safety of operators of filling stations. This is key to ensuring your safety and the safety of those around you. Scuba divers may dive with a single cylinder, a pair of similar cylinders, or a main cylinder and a smaller "pony" cylinder, carried on the diver's back or clipped onto the harness at the sides. This all depends on diver preference so look into which set up will be best for you.
