When gas is drawn off from the container, part of the liquid vaporises and in so doing becomes cooler. No air flows into the gas container. If a large quantity of gas is drawn off, the liquid cools to below 0°C and the container freezes. At or preferably before this point, the user should stop removing gas or reduce the flow. Attempting to carry on extracting gas will cause the pressure in the container to fall even further and the flow of gas will ultimately cease, even though liquid LPG is still present in the canister. In this state it will not flow out, even if the canister is left unsealed. However, if the canister subsequently warms up, the gas will begin to flow again unnoticed, a situation that can give rise to fires or explosions.