In scuba diving, a freeflow occurs when the diving regulator continues to supply air instead of cutting off the supply when the diver is not breathing in.[1] This may be caused by very cold water freezing the second stage valve open, a malfunction of either the first or second stages, or by the venturi effect on very sensitive demand valves keeping the internal pressure low enough for the valve to stay open. If the freeflow is caused by freezing, then switching to an alternative air supply briefly should allow water that fills the second stage to unfreeze it. Otherwise, simply replacing the valve in the mouth and attempting to breathe normally will usually resolve the problem.[1]