What Happens If You Run Out of Air While Scuba Diving?

Last Updated: November 30, 2023

Scuba diving is a thrilling adventure activity and the adrenaline rush you get from swimming underwater is unbeatable. Quite a few potential risks are involved, though. Perhaps that’s what makes it so exciting.

Many scuba divers live with a fear of running out of air during a dive. And unfortunately, it is quite a valid concern.

The oxygen tank and air gauge are two pieces of equipment that support your life underwater. The importance of oxygen becomes highly evident when you see the air emptying from your tank.

Even though air management is one of the first things to keep an eye on while diving, it can still become an issue.

Read on to learn the possible causes of running out of air and how you can handle it.

Why Do Divers Run Out of Air?

what to do if you run out of air when scuba diving

Knowing how important an oxygen tank is, air management is a priority for scuba training. But there can be multiple reasons that can lead to mismanagement, and you end up losing more air than anticipated.

There are several reasons for your oxygen tank emptying faster than expected.

Deeper Dive

Deep diving requires a lot more oxygen than a recreational dive.

A lot of recreational divers exploring the shallow waters might get intrigued by what they see deeper down. As a result, they might dive deeper with a tank capacity that was sufficient only for a shallow dive.

As you dive deeper, your oxygen expense increases. That means a tank that was supposed to last you around 60 minutes in shallow waters will go down to 17 minutes when you dive deep.

Apart from that, a deep dive requires multiple decompression stops to avoid the build-up of nitrogen bubbles in the body.

If you start running out of air, you will have to pace up your ascent and put your body at risk of insufferable pain after reaching the surface.

It is, therefore, important to stay within the limits of your air tank.

Poor Air Management

Even though it is a part of the diving training, people still end up managing air poorly. As a result, they run out of air in between, leading to an emergency ascent.

The primary reason for the shortage of air supply is poor air management.

Since the sea is highly fascinating and mesmerizing, divers get lost in the view and exploring new things. They forget to monitor the gauge or keep continuous communication with their peers.

That can prove to be risky. So along with enjoying the view monitoring your oxygen level is necessary.

Failure in Equipment

Equipment failure might not be common, but it is one of the causes to look out for.

There can be many reasons for an equipment failure. The riskier ones include a free-flowing regulator, which will empty your air tank more quickly than expected.

Some of the other common issues include:

  • Pressure gauge problems
  • Partially open tank
  • BCD tears
  • Computer error in pressure gauge


Anxiety is a highly intensive emotion. It causes heavy breathing and palpitations.

When you are underwater, there is a possibility of being struck by anxiety. Especially for first-time divers, the sea can be pretty intimidating and scary.

Being anxious can result in higher oxygen consumption from the tank. You will feel uncomfortable and create a risky situation for yourself.

Though it is not possible to control the occurrence of an axiety attack, you can prevent it from overpowering yourself. If you face anxiety during the dive, you will feel your breathing rate is going up.

The moment you sense it, keep an eye on your air gauge and start an ascent. Make sure you reach the top safely.

What Happens When a Diver Runs Out of Oxygen?

As mentioned earlier, running out of air in between the dive is pretty common.

If your tank is running low on gas, your time underwater will reduce significantly. Instead of exploring, your focus should then get diverted towards making an ascent.

Divers with low oxygen levels are forced to begin an emergency ascent. That means you may need to reduce or eliminate any decompression stops.

Due to a forced upward swim, the air will remain decompressed in the body, causing painful bends as you reach the surface.

Spotting a shipwreck and going for the exploration might appear thrilling, but it can turn out to be highly risky. Maintaining air level and monitoring your gauge is a necessity that you should not forget.

What to Do If You Run Out of Air When Scuba Diving?

Fortunately, there are a few things that you can do to make your ascent easier if your tank runs out of oxygen. However, using these options depends on multiple variables that are around you.

Whatever appears suitable for you, at that moment, should be your action plan.

Here are some of the options you can use, depending on the circumstances, when your tank runs out of air.

Air Sharing

It is one of the most commonly used methods during diving. Most of the time, divers always go for a dive with a partner or a small group. In case your tank is running short, locate your buddy.

If you are closer to the surface than your fellow diver, the sensible thing will be to continue an ascent. But if they are closer, sharing air from their tank should be your go-to option.

In such a situation, communication is the key. Indicate to them your need and take their backup regulator to support yourself.

The moment you are supported by the air supply from the other tank immediately begin your ascent.

Your ascent should be slow and controlled as the two of you are reliant on one tank.

Don’t be over-enthusiastic and complete your exploration with the common tank. You will be putting two lives in danger. Instead, use the extra air to make decompression stops for a safer ascent.

Ascending Normally

In case you can detect the lowered air supply at a considerable time, there is a possibility that you can do a normal ascent.

A regular ascent at the usual rate will help you reach the surface without any additional problems.

That is because, when you start your ascent, the air in your tank starts expanding, providing you with enough supply to breathe.

That makes it possible to recover a sufficient amount of air for a normal ascent. Sometimes the air level might rise faster than you expected. You will have to dump it through the BCD to keep the levels controlled in such a situation.

Emergency Swimming Ascent

ESA is one of the skills you get introduced to during your open-water certification course.

This ascent is significantly faster than the usual ascent as the aim is to reach the surface as soon as possible.

In an ESA, you must swim in an upward direction, with one hand up and expelling air as you move.

It will help if you breathe out continuously to ensure that you are not holding air in your lungs to prevent causing any potential injury. The reason you keep your hand raised is to protect your head from hitting something when you reach the surface.

The use of ESA should be left only to the worst possible cases. In shallow depths, ESA works fine. But when you go deeper, decompression stops become a necessity. If there is no other option left, subjecting yourself to decompression sickness is the most sensible choice to go with.

Redundant Air Supply

Some divers anticipate their risks beforehand and keep a redundant air supply system along with them. It is carried like a spare tank and is also known as a pony tank.

A pony tank helps minimize the need to share air in case of an emergency. A redundant air supply can help you achieve a descent in a more controlled and safe way. Your chances of facing decompression sickness and drowning get reduced significantly.

Final Thoughts

Scuba diving is fun and adrenaline-pumping only when you pay attention to your safety.

Being educated about your risk is not being negative. It is a step forward in being prepared if you fall prey to any dangers undersea.

Stay close to your diving buddies, communicate properly and be vigilant about your air supply. Being careful about these pointers will help you have a safe and adventurous dive that you can cherish forever.

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