Rescue may be needed for various reasons where the diver becomes unable to manage an emergency, and there are several stages to a rescue, starting with recognising that a rescue is needed. In some cases the dive buddy identifies the need by personal observation, but in the more general case identification of the need is followed by locating the casualty. The most common and urgent diving emergencies involve loss of breathing gas, and the provision of emergency gas is the usual response. On other occasions the diver may be trapped and must be released by the rescuer. These first responses are usually followed by recovery of the distressed diver, who may be unconscious, to a place of safety with a secure supply of breathing gas, and following rescue, it may be necessary to evacuate the casualty to a place where further treatment is possible.