The Oxygen Canisters have a shelf life of 2 years. It is still safe to use the oxygen canisters past the expiration date, as the 2-year shelf life covers the canister itself, rather than the oxygen it contains. We recommend testing to make sure your canister contains oxygen past the expiration date, as past that time, the pressure seal on the canister is not guaranteed. You can use the pressure gauge on your regulator to test whether the canister is still full, which indicates that your pressure seal is intact.