The Helicopter Aircrew Breathing Device or HABD (also known as a Helicopter Emergency Egress Device HEED or SEA [clarification needed] [1]) is an item of survival equipment which was adopted by the military to increase the chances of survival for embarked troops and aircrew trapped in an aircraft which has ditched (crashed into a body of water). It is a form of self contained underwater breathing apparatus (scuba) which consists of a small cylinder pressurized with atmospheric air and first stage regulator worn in a pouch on the user's life vest; a pressure gauge; an air hose and a second-stage demand regulator that delivers air to the user's mouth when the internal pressure of the mouthpiece drops during inhalation, and is ruggedly constructed to survive impacts associated with emergency ditchings.