What you need to know about compressed gas containers
Laws regarding compressed gas tanks (aka “cylinders” or “bottles”) are enforced by the United States Department of Transportation. There are a variety of issues that need to be taken into account before having your cylinder filled.
Is it your cylinder?
Although you may have paid for the tank in your possession, it doesn’t mean that it belongs to you. Some tanks are metal-stamped with identification marks designating their proper owner.
Is it in date?
Every 5 or 10 years compressed gas containers need to be subjected to a hydrostatic test. The last date will be stamped on the cylinder near the valve and consist of the month and year the tank was last tested.

Bottom Line: Policy and Laws about filling tanks vary from region to region. You can own any size tank your heart desires, it is a matter of who will fill them.