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How Long Do Rebreathers Last? Answered

How Long Do Rebreathers Last?

Switching to a rebreather from a regular open-circuit scuba tank is a good idea.

Rebreathers make use of the gas you exhale in a recycling form which allows for longer dives.

It does this by taking the good part of the exhaled gas and supplying it for your next breath.

In other words you have a bigger gas supply packaged for you in comparison with what you get in your regular open-circuit scuba tank.

The rise in the use of rebreathers in recent years despite it being in existence since around the early 1940s, has sparked a lot of interest in people who do not know much about it.

Are you wondering how good rebreathers are, if it is safe to use, if they are better than regular open-circuit scuba tanks?

The real question for why we are here, is how long do rebreathers last? Well then let's find out, shall we?

How Long Do Rebreathers Last?

The longest a rebreather can last is about 2 to 3 hours at the most, however, some factors can limit or increase this time frame.

There is a CNS oxygen toxicity clock and scrubbers which are used to remove carbon dioxide from the gas that is recycled.

This gives a duration of 2 to 3 hours max this is based on a regular scrubber type.

The gas supply for your rebreather also plays a huge factor in how long your rebreather will last. 

There is a difference in how long the rebreather would last based on a gas supply from a 3-liter gas cylinder and a 2-liter gas cylinder.

The 3-liter gas cylinder can give around 5 hours or even a bit more, while the 2-liter gas cylinder would give at least 2/3 hours at most.

The harder you work during the dive the faster you breathe, and the faster you breathe the faster your gas finishes. 

So how hard you work during the dive also affects the time limit.

So, the bigger the liters of the gas cylinder is, the longer the rebreather lasts. 

This is because there is more gas to inhale, exhale, and to be recycled for the next breath that you take.

Additional Information

Rebreathers are made with a CO2 scrubber that is used for absorbing carbon dioxide found in the breath exhaled by the person using it.

Rebreathers are closed-circuit breathing equipment that recycles the air exhaled, they take the unused oxygen from the air exhaled add it up to that in the gas cylinder and it becomes breathable again.

The oxygen assimilated by the user would be equal in amount to the oxygen that has been restocked. However, the ratio of oxygen that is added to the gas gets optimized.

This is because of the depth of the diver, it optimizes the oxygen added to the gas to keep the partial pressure of the oxygen safe for the depth the diver is diving at.

The longest rebreather dive that was recorded was 9 hours and 40 minutes, this was done by an Australian diver. 

His name is Davis Shaw, he set this record in a cave called the “Boesmansgat Cave”. He dived as deep as 886 feet which is the depth of 270 meters, which is very deep.

Navy seals are one of the people who make use of rebreathers the most as it helps them carry out their activities underwater even better. 

Where a regular open-circuit dive tank would send bubbles to the top, the rebreather takes that exhaled air and recycles it, so no bubbles.

Navy Seals are trained to stay underwater longer compared to regular divers, despite how hard they work. 

They can stay underwater for about 4 hours in warm water and 2 hours in cold water.

They still pull this off despite their work rate and the amount of carbon dioxide they generate, highly impossible for a regular diver to pull off under the same conditions.

The length of their underwater time is also limited by the scrubber on their rebreathers as they make use of a specific rebreather known as “Drager Rebreathers”.


For a regular scrubber in a rebreather, it lasts 2 to 3 hours max. 

However other factors have been able to reduce or increase this time frame, like that of the gas cylinder which can reduce or increase this time frame depending on the liter of the cylinder.

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