About Scuba Tanks

Scuba tanks are critical to a diver's underwater life support system. Any scuba tank will store air. However, divers can select tanks of the right material and size to make diving more enjoyable and safer. Divers also must ensure that their tanks have been tested for safety on a regular basis.

  1. The Facts

    • Scuba divers need a source of air while diving. Scuba tanks store pressurized air during dives and are attached to a regulator that controls the flow of air to the diver's mouth. Scuba tanks resemble the large metal tanks used in stores to contain the helium used for blowing up balloons, but they are smaller so they can be carried on a diver's back. The tanks are made of either aluminum or stainless steel, and come in different sizes for various purposes. A diver typically carries one to three tanks, depending on the type of diving he does.

    History

    • Scuba tanks for non-military use first became available in the United States in the late 1940s. After the famous ocean explorer Jacques Cousteau patented his scuba diving system, called the "Aqua Lung," in the early 1940s, scuba diving gradually replaced "breath-hold" or free diving, as the dominant diving technique in the United States. The ability to carry one's own air in tanks on a dive made underwater adventures easier, pleasurable and accessible to a wider variety of divers.

    Types

    • There are numerous types and sizes of scuba tanks. The primary differences are in material and size. Aluminum tanks are most common and are cheaper. However, aluminum tanks gradually become positively buoyant during a dive as the diver uses up air, requiring the diver to compensate for this buoyancy to avoid its pull toward the surface. Steel tanks, the more expensive option, instead become neutrally buoyant as air is used, not affecting the diver's overall buoyancy.

      Scuba tanks are sized by the amount of air they can hold. The most common tank available from scuba shops is an aluminum 3,000 psi tank that holds about 80 cubic feet of air. However, tanks range from 2,400 psi to 3,500 psi and 65 to 100 cubic feet of air.

    Warning

    • Divers should use caution when selecting a tank to purchase or rent. In the United States, regulations from the U.S. Department of Transportation require that all scuba tanks undergo an annual visual inspection and a hydrostatic test every 5 years. The hydrostatic test verifies that the tank is still sound and will hold up under the pressures of diving. If you are unsure about a tank's history, be sure to ask for records of its use and testing.

    Potential

    • Another recent development in scuba tanks has been the widespread availability of smaller backup tanks for emergency use during dives. Cave divers have for many years carried smaller "pony bottles" with them for risky situations; however, many recreational divers are now carrying pony bottles as well. These small tanks can easily be attached to a diver's buoyancy compensator (BC) vest, and they can hold 3 to 15 cubic feet of additional air. They may also have a built-in regulator, so they can serve as a breathing system in the event of an out-of-air situation or a primary regulator malfunction.