How long may a tourniquet used to stop bleeding remain in place?

Explanation

A tourniquet stops blood flow to the whole part of the limb below it, and the tissues get no oxygen, so it cannot stay on indefinitely. The limit is 1 hour in warm weather and half an hour in cold weather, because a limb without circulation cools quickly and risks frostbite. That is why a note with the time of application is attached to the tourniquet.