A tourniquet is generally reserved for severe, life-threatening bleeding from an arm or leg that cannot be controlled by direct pressure alone. Common signs of life-threatening bleeding include blood that is spurting, pooling, or rapidly soaking through bandages.
Whenever possible, use a commercially manufactured tourniquet designed for medical use rather than an improvised one.
Once a tourniquet is applied, it should only be removed by a qualified medical professional in a clinical setting.