Safety
Out-of-Air Emergency — What It Is and Why It Matters
An out-of-air emergency occurs when a diver's air supply is depleted or their regulator fails, cutting off their breathing gas. This is one of the most serious emergencies in diving because the diver cannot breathe and must act quickly. Response options in order of preference: switch to buddy's alternate air source, switch to your own alternate air source (pony bottle, if carried), or perform a controlled emergency swimming ascent (CESA).
Out-of-air emergencies are almost entirely preventable through proper gas management — monitoring your SPG or air-integrated computer throughout the dive, planning turn pressures, maintaining an adequate reserve, and diving within your training limits. Your dive computer's air time remaining (ATR) function exists specifically to prevent this scenario.
Frequently Asked Questions
How do I prevent running out of air?
Monitor your pressure gauge or air-integrated computer frequently — at least every 2 to 3 minutes. Plan your turn pressure (typically half-tank or at a pre-agreed pressure). Follow the rule of thirds for planned deeper or longer dives. Start your ascent early rather than late. Use your computer's low-air alarm settings.
What should I do if my buddy is out of air?
Present your alternate air source immediately — hold it out, make eye contact, and stay calm. Once they are breathing, control the situation by holding their harness or BCD. Begin a slow, controlled ascent together. Maintain close contact throughout the ascent and safety stop. Practice this scenario with your buddy regularly.
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