There are two types of propane containers, the ASME tank and the DOT cylinder. NFPA pamphlet 58 states that all DOT cylinders need to be recertified after 12 years from the manufacturing date and depending on what certifying method is used they are recertified every 5,7,12 years thereafter. Recertification involves a periodical documented inspection and testing of the cylinder to confirm that the cylinder is still safe and legal to remain in service.

ASME tanks do not get recertified. They should have the relief valve replaced every 10 years and follow the same standards established by the Dept. of Transportation.