How A UK Roy Nav Submarine Purifies It’s Own Air

Submarines have always amazed me. Learning about different vehicles when growing up was always a joy, but the submarine was the one that consistently captured my curiosity and intrigue.

And one of the main questions I had about these vehicles was how they were supposed to produce air on their own.

These machines spent extended periods of time completely submerged in the water; how in the world were they able to get air?

Well, this is how I stumbled upon the HMS Astute, a UK Royal Navy Submarine that purified its own air. This simply blew my mind, and it could be one of the main reasons I’m so interested in air purifiers as an adult.

So today, I’m finally going to be able to talk about something that racked my brain for many years as a kid: how submarines produced breathable air.

We’re looking at the common methods submarines use to purify the air, how they work, and some of the actual submarines that use these pieces of technology today.

How Submarines Create Breathable Air

While the UK Royal Navy has had submarines for a long time, they were able to completely change the game with the HMS Astute S119, which was considered one of the first of its class. While she was a nuclear submarine, one of her key features was her ability to purify her own air for the crew.

The HMS Astute S119 is a fairly new submarine, but she can purify air to such a degree that the ship can navigate the entire world without reemerging for air, which is a completely new concept.

With that said, the first air-independent submarine can be traced back to 1864, so why did it take that long to come up with this incredible technology?

Well, that story is a bit complicated. But we’re now at a point where there are many ways that submarines create breathable air, so let’s take a look at the most common ways modern submarines purify and introduce oxygen to the air.


This is the most common way submarines create breathable air. This method involves extracting oxygen from water, which submarines always have access to.

This process works by first removing all the impurities like salt from the water, which most submarines do by heating the water up.

After that, the submarine introduces an electrical current into the water, which causes the oxygen molecules to separate from the hydrogen in H2O.

From there, the submarine can start introducing the new air into the cabin, giving the crew clean and good air to breathe.

Oxygen Candles

Also known as a chloric candle, this is a candle with a mixture of iron powder and sodium chlorate. When you ignite these candles, they can produce a fair amount of oxygen.

This is commonly used as an emergency oxygen source as you can store these candles for a long time without diminishing the oxygen levels they can produce.

CO2 Scrubbing

This is the process of removing CO2 or carbon dioxide from the air. To “scrub” the CO2, the crew uses scrubbers.

These scrubbers have sodium lime which can trap CO2 and leave clean and breathable oxygen for the crew to breathe. 

Some submarine crews also use lithium hydroxide canisters to scrub the CO2 as there are many different ways to remove CO2 from the air.

This is an essential part of running a submarine and something that’s always present in the equipment compartment.


Some submarines use only one of the above techniques, while others use a combination of them to produce enough oxygen to last the crew a very long time.

With that said, the exact details of how some submarines produce air are hard to find as this is sensitive information that should be kept on the down-low.

While this is frustrating, it also adds to the mystery of submarines. But rest assured, the second we find new technology and ways to produce air on a submarine, I’ll be there to talk about it.

‘Til next time!