SodaStream CO2 cylinders are totally safe to have in your home. They are manufactured to exacting safety specifications to protect our consumers and are safe at virtually any altitude (our customers in the Swiss Alps can attest to that!). Our cylinders are specially equipped with a safety valve that will harmlessly release the gas in the unlikely event that the pressure within the carbonating cylinder rises above threshold levels. Make sure to always store your CO2 cylinder in a cool and dry environment, away from direct sunlight. The carbonating cylinder must not be exposed to sources of heat (such as prolonged travel in the trunk of a car) or placed right next to a heat source such as an oven, stove or fireplace.