How to Avoid and Deal with Running Out of Air


There’s really no reason you ever find yourself running our or air. As long as you monitor you pressure gauge, and plan your dive correctly you should have enough air to finish a dive after a safety stop and a slow safe ascent to the surface.

What is the difference between running out of air and running low on air underwater?

Running low on air when scuba diving simply means it’s time for you to abort the dive, though you still have ample supply of air to complete the recommended safety stop and to slowly ascent to the surface. Scuba tanks shouldn’t be emptied completely as air pressure inside the tank prevents water and moister from entering it, corroding its interior. We should finish our dive with about 500psi, 35 bar of air pressure in our tank, meaning we need a bit more than that to start aborting our dive. Running Low on air isn’t life threatening, there’s still enough time to finish the dive.

The universal signal for running low on air is a feast held close to the chest.

Running out of air while scuba diving means you’re about to, or completely have finished your air supply and emptied your tank. Running out of air underwater is risky and demands immediate attention and response as will be described later in the article.

The universal sign for running out of air is a clear throat slitting motion.

How to avoid running out of air?

1. Monitor your air pressure frequently.

Some advanced Dive Computers allow you to monitor your tank’s pressure through transmitters attached to the tank. You can also monitor your buddy’s air supply as well using that feature, increasing safety furthermore. Otherwise, just check your pressure gauge occasionaly and follow your dive plan allowing enough time for getting back to the exit point , completing a safet stop and ascending to the surface.

2. Plan you dive properly.

When planning a dive you should limit yourself to the NDLs the No Decompression Limits, but it doesn’t mean neglecting your air supply limitation.

Remember, air consumption is individual and is effected by many variables.

Learn how to save air and dive longer here.

You can roughly estimate air consumption rate using this simple formula:

Air consumption at the surface*(1+depth in m /10)

For example a diver at 20 m, will consume air 3 times faster at 20m:

Surface air consumption*(1+20/10)=S.A.C*3

A good trick is to plan your dive backwards:

A. Allow 40bar / 500psi at the end of the dive, to prevent water and moisture from entering the tank and corroding its interior.

B. Allow some air for a minimum 3 minutes safety stop. (An estimated 20bar/300psi)

C. That leaves about 2200psi/140Bar for the rest of your dive.

D. you can keep adding more elements, such as moving from and away from the exit point (takes about the same time, air consumption varies depending on depth changes) or Multilevel Dive Plan, where at each depths you consume air in deferent rate.

Out of Air Emergency Procedures:

If eventually you run out of air, it’s important to Stop, Think, and finally Act according to the best solution possible, baring in mind that a rapid ascent to the surface may pose a serious risk of Decompression Sickness.

Use The sentence No Air Can Be Bad, and the acronym N.A.C.B.B that will help you remember the order of alternatives you have in an out of air emergency:

1. Normal Ascent.

Slowly ascend to the surface no faster than 18m/60ft per minute.

2. Alternate Air Source

. If out of air, your best option is to find your buddy, signal “Im out of air” locate and secure his AAS and ascend with him to the surface.

3. C.E.S.A – Controlled Emergency Swimming Ascent-

.If out of air, and can’t reach your buddy, you can inhale deeply and slowly ascend to the surface making a continuous AHHHHH sound, while keeping the regulator in your mouth. As most of us can exhale slowly for more than 25 seconds, you should be able to complete a slow ascent from 20ft/6m without exceeding maximum ascent rate.

4. Buddy Breathing

a similar option to AAS, where here we use a single regulators for two divers, which requires more coordination and practice. The skill is optional at the Open Water Course.

5. Buoyant Ascent-

Your worth case scenario, should not be practiced fully. Only if you’re:

A. Out of air.

B. Far away from your buddy or cannot find him.

C. in water to deep to perform C.E.S.A

Remember that all the above scenario should be avoided; putting yourself in that position is nearly 100% due to human errors.

At this point all you can do is to remove your weights, and float up. Its important to spread your arms and legs and stay horizontal to slow down ascent rate, and remember to continuously exhale making an AHHHH sound.

Running out of air can lead to serious consequences. Remember, as long as you plan your dive and dive your plans, most dive accidents can be easily avoided.

If you still managed to find yourself in an emergency situation the most important thing is to relax, stop, think and only then act.

Your Open Water scuba skills should prepare you for the worse case scenario; keep your skill level up to date.

If your not to comfortable with your skills- consider a quick refresher course, or upgrade your scuba credentials.

Have fun and dive safely.

Knows-dive team


  1. If my air decreased very rapidly and there was water in my regulator as my tank got low, does that suggest a leak?

  2. Low on air tanks should still provide enough air pressure to prevent water from entering the second stage.
    The second stage (regulator) may get water in it as a result of leakage, maybe the diagphram is misplaced or damaged, but that will also cause water leakage on full tank.
    Did you experience any problems with a full tank? That would definitaly indicate a second stage problem, and may very well cause rapid air decrease .
    You can set up your gead and test it in a bucket full of water, see it there are any problems there, or head to your local dive shop and ask for a full system test, as it is recommended to do so anyway regularly.
    Hope that helps.

  3. Hi,

    I just recently got my license & certification as an open water diver. I thoroughly enjoyed it and now look forward to the next dive.

    My burning question though: is you are able to exhale slowly w an “ahh” sound for 40 secs, does this mean you can safely CESA from 40 ft? If 60 secs, 60 ft?. Is it correct to say that since air is much much more compressed at the bottom, theoretically you wont run out of air (CESA) from even 100 ft.

    sorry for the question. But i would highly appreciate your expert comment.

    Thanks, Jay Capino

  4. Hi Jay.
    Interesting question.
    With maximum ascent rate of 60ft/min you should be able to ascend from 40ft if you are able to exhale for 40 seconds. It is also true that air in you lungs will expand as you ascend, so you basically do have “more air” when ascending than swimming vertically. So, in theory, you should be able to ascent safely from even deeper depths. Using the same amount of air to ascend from deeper water (100ft) theoretically is possible but not really recommended, especially considering other factors such as variation in oxygen consumption, exhalation rate, anxiety and other factors. That’s my humble opinion.
    So to sum it up.
    CESA is possible to be accomplished from deeper water, yet not recommended. If you must, I guess that is what you will have to do, while being prepared to remove your weights in case you have no air left while ascending.
    In reality, you should never get to the point when you should ever perform a CESA.

  5. thank you very much tobi1kenobi. your advise helps put to rest that burning question of mine. cheers!

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