How Long Should Air Be Left in a SCUBA Tank?

How Long Should Air Be Left in a SCUBA Tank?
Many divers keep SCUBA tanks filled and ready in anticipation of future dive trips. A filled SCUBA cylinder may be stored up to a year. The limitation on stored air in a SCUBA cylinder relates to the timetable for regular maintenance of the cylinder.

Shelf Life of Air

Air in a SCUBA cylinder will not spoil. Of primary concern is the presence of moisture and contaminants. Air compressors used for life-support equipment remove much of the moisture content of air and prevent many contaminants when operated and maintained properly. Without moisture, the oxygen in the air is not a factor in corroding the metal of the cylinder.

Cylinder Metals

Cylinders are constructed of steel or aluminum alloys. A small percentage of aluminum 6351-alloy cylinders have displayed sustained load cracking (SLC) from prolonged storage when full. These cylinders still are in use and underscore the need for a regular service inspection of the cylinder.

Visual Inspection

SCUBA cylinders filled less than five times a week should be visually inspected by qualified personnel once a year.

Hydrostatic Testing

The US Department of Transportation requires SCUBA cylinders to be hydrostatically tested once every five years.

Special Circumstances

A SCUBA cylinder that has been improperly stored, mishandled or show signs of damage should be visually inspected before being put back into service. Cylinders exposed to high heat, such as a house fire, should be hydrostatically tested.

Proper Storage

SCUBA cylinders should be thoroughly rinsed with fresh water following use. Store with positive pressure inside the tank to prevent moisture from entering, at room temperature, and in an upright or horizontal position where they will not roll, tip, fall, or be damaged.

Article Written By David Chandler

David Chandler has been a freelance writer since 2006 whose work has appeared in various print and online publications. A former reconnaissance Marine, he is an active hiker, diver, kayaker, sailor and angler. He has traveled extensively and holds a bachelor's degree from the University of South Florida where he was educated in international studies and microbiology.

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