Oxygen tanks for water sports hold between 50 to 150 cubic feet of air. Diving tanks come with different pressure ratings.
Oxygen tanks for scuba diving are high pressure cylinders containing compressed gas. There are three pressure ratings, which are measured in pounds per square inch (psi):
- Low: 2,400 to 2,640
- Standard: 3,000
- High: 3,000 to 3,500
There are also specialty high-pressure steel tanks that require a Department of Transportation (DOT) permit. Tanks are identified by prefixes. For example, aluminum tanks are labeled with the prefix "AL," low-pressure steel tanks are labeled "LP" and high-pressure steel tanks are labeled "HP." Recreational divers often use tanks with a capacity of between 50 to 100 cubic feet of air, while many rental tanks typically hold 80. Pony tanks, which hold up to 40 cubic feet, are used as a back-up air supply.