OOA (Out of Air) – An Emergency Situation in Scuba Diving


OOA, or Out of Air, is a critical emergency situation in scuba diving where a diver’s supply of breathing gas is depleted or interrupted. This can be a life-threatening event as it may lead to panic, injury, or even death, particularly if the diver is at significant depth or far from the surface. As such, it is essential for divers to understand the causes, prevention, and management of OOA situations to ensure their safety while exploring underwater environments.

Causes of OOA:

  1. Equipment Failure: One of the primary causes of OOA is equipment malfunction or failure. This can involve a regulator failure, a burst or disconnected low-pressure hose, or a sudden tank valve closure.
  2. Gas Supply Depletion: An OOA situation can occur when a diver consumes their entire gas supply, either due to poor air management or an extended dive time. In some cases, this may result from the use of an incorrect gas mixture or diving deeper than planned.
  3. Entanglement or Entrapment: A diver may become trapped or entangled in underwater structures, such as wreckage or kelp, resulting in the inability to reach their air supply or effectively manage their air consumption.
  4. Human Error: Miscommunication, lack of awareness, or inattention to gauge readings can result in a diver failing to notice their dwindling air supply.

Prevention of OOA:

  1. Pre-Dive Checks: Conduct thorough equipment checks before each dive, ensuring that all components are functioning correctly and that connections are secure. This includes inspecting the regulator, hoses, tank valves, and pressure gauge.
  2. Dive Planning: Plan and execute dives within the limits of one’s training, experience, and equipment. Utilize a dive computer or dive tables to monitor the dive profile and ensure that the dive remains within safe limits.
  3. Air Management: Regularly monitor air consumption throughout the dive, and adhere to the rule of thirds: reserve one-third of the air supply for the return journey, one-third for emergencies, and use the remaining third for the planned dive.
  4. Communication: Establish clear communication protocols and signals with dive buddies, ensuring that all divers understand and agree on the dive plan, maximum depth, and turnaround points.
  5. Training and Practice: Regularly participate in refresher courses and practice emergency scenarios, such as sharing air with a buddy or performing a controlled emergency swimming ascent (CESA).

Managing an OOA Situation:

  1. Stay Calm: In an OOA situation, it is crucial to remain calm and focused. Rapid breathing and panic can exacerbate the situation, making it difficult to think clearly and act appropriately.
  2. Signal for Help: Immediately signal to your dive buddy or the surface support team that you are out of air. Use established hand signals, such as the “out of air” sign (a cutting motion across the throat), or deploy a surface marker buoy (SMB) to alert the surface team.
  3. Share Air: If possible, locate your dive buddy and establish a shared air source, such as an alternate air source (octopus) or buddy breathing from the same regulator. Maintain physical contact with your buddy while sharing air to prevent separation.
  4. Ascent: Once a shared air source is established, begin a controlled ascent to the surface, observing proper ascent rates and safety stops if necessary. If the situation is dire and a shared air source is not available, perform a controlled emergency swimming ascent (CESA) to the surface, exhaling slowly and continuously to avoid lung over-expansion injuries.
  5. Surface Support: Upon reaching the surface, signal for help, establish positive buoyancy, and await assistance from the surface support team.


OOA situations can be alarming and potentially dangerous. However, by following proper dive procedures, maintaining regular training, and practicing emergency scenarios, divers can significantly reduce the risk of experiencing an OOA event.

To further minimize the likelihood of an OOA situation, divers should also consider the following:

  1. Equipment Maintenance: Regularly service and maintain dive equipment according to manufacturer guidelines. This includes replacing worn or damaged parts and checking for signs of wear or corrosion that may compromise the integrity of the equipment.
  2. Gas Management Techniques: Utilize gas management techniques such as the “rule of thirds” and adhere to conservative dive profiles to ensure a sufficient supply of breathing gas throughout the dive.
  3. Dive Briefings: Attend comprehensive dive briefings and familiarize yourself with the dive site, potential hazards, and emergency procedures. Make sure all divers understand the plan and have agreed upon communication signals and procedures.
  4. Buddy System: Diving with a buddy or a group is essential for safety. Ensure that the buddy team has compatible equipment, dive objectives, and experience levels. Regularly check on your buddy throughout the dive and maintain close proximity to facilitate communication and assistance in an emergency.
  5. Continuing Education: Pursue advanced scuba diving certifications and specialized training, such as rescue diver or technical diving courses, to enhance your knowledge, skills, and preparedness for a variety of diving situations.

In conclusion, OOA situations are a critical concern for scuba divers, as they can lead to severe consequences if not managed effectively. By understanding the causes and implementing preventative measures, divers can significantly reduce the likelihood of encountering an OOA situation. Additionally, by maintaining regular training, practicing emergency procedures, and ensuring proper communication, divers can effectively manage an OOA situation, should it arise, and mitigate the associated risks.

By fostering a culture of safety, responsibility, and ongoing education within the diving community, we can continue to enjoy the wonders of the underwater world while minimizing the risks associated with OOA and other diving emergencies.