Composition

• Scuba tanks are also called cylinders, and most are composed of steel or aluminum. Steel tanks are heavier and less susceptible to damage, but they can rust after prolonged use. Aluminum scuba tanks cost less than steel ones, but they require more maintenance.
  
  

Codes

• The Department of Transportation (DOT) requires that codes be placed on scuba tanks. The codes indicate whether the tanks are steel or aluminum, the rated service pressure in pounds per square inch (PSI), the manufacturer and the date of the last inspection.
  
  

Safety

• Scuba tanks should generally not be filled above their PSI code level, which is stamped on the side. Over-pressurized tanks can explode, injuring a diver or damaging a boat or other property.
  
  

Testing

• Scuba tanks should be inspected once a year for physical damage, including cuts, stress lines and dents. The thread where the scuba tank connects to the tank valve should also be inspected.
  
  

Hydrostatic Testing

• A more thorough test on scuba tanks is a hydrostatic test. The tank is subjected to over-pressurization to determine its structural integrity.