Out of Air

An emergency in which a diver has no breathable gas left, resolved by sharing a buddy's alternate air source or making an emergency ascent.

Out of air is the emergency every course prepares you for: your regulator suddenly gives nothing, whether from an empty tank, a valve problem, or an equipment failure. The trained response is immediate and ordered. Signal your buddy with the throat-cutting out-of-air sign, secure their octopus, restore normal breathing, and ascend together at a controlled rate. If no buddy is within reach, a CESA, the controlled emergency swimming ascent, lets you reach the surface from moderate depth on the expanding gas in your lungs while exhaling continuously.

Almost all out-of-air situations are preventable, which is the real lesson. They trace back to not monitoring the SPG, misreading gas needs at depth where consumption is higher, or poor gas management. Planning a turn pressure, applying reserves like rock bottom or the rule of thirds, and checking gauges every few minutes make running empty extraordinarily unlikely. Redundant sources such as a pony bottle add another layer for deeper dives.

Air-sharing drills are worth refreshing regularly, not just at certification. A team that has recently practiced a calm octopus exchange and ascent will handle the real thing as a procedure rather than a panic. Practicing both roles matters, donor and receiver, and so does rehearsing the follow-through: establishing contact, controlling buoyancy, and making the ascent as a connected pair rather than two divers pulling in different directions.