Our oxygen canisters are designed, quality-controlled and filled in the U.S.A., and O+ canisters are 100% recyclable after use. Oxygen Plus is the only portable recreational oxygen filled in the U.S.A. in a FDA-registered facility. Oxygen Plus is designed for optimum convenience. The oxygen flows stronger with a new canister, and dispenses more slowly as you use it. The canister is completely empty when the oxygen flow stops while the actuating button is depressed. Each O+ oxygen product states “Best by 24 months from fill date” on the canister. The fill date is located on the bottom of each canister. While the gas of oxygen itself never expires, we added this "shelf life" or product lifespan timeframe to ensure you're completely satisfied with the value of your purchase well beyond the typical time you'd finish a canister. After 24 months, O+ products will still work and are safe to use if stored as directed, however a user may experience slightly fewer “breaths.” FYI, a canister that's been opened or used does not expire any faster than an unopened canister.