Electrolysis is a method used by submarines to generate oxygen. This process involves passing electricity through water causing it to break into hydrogen gas and oxygen gas. Electrolysis is also used to produce oxygen for submarines out of seawater. This involves removing the salt off the seawater to produce freshwater for further process. However, this is important as the salt may destroy the electrolysis engine itself in some cases. The electrolysis machines are fed with seawater which is desalinated. An electrolytic machine is used for electrolyzing water in order to form hydrogen and oxygen gases. Hydrogen escapes overboard while the oxygen is fed into pressure storage.  

These oxygen tanks feed fresh oxygen into the submarine to keep the crew alive. Oxygen also serves as a means of refreshing the air in the submarine and some appliances like fuel cells.  

The electrolysis process is highly effective in producing oxygen, although it needs an electric current. Submarines use nuclear reactors for generating electricity, and therefore, can provide fresh air to them while underwater.  

Apart from electrolysis, there are numerous reserve facilities for the production of oxygen in submarines. These systems include: 

• Oxygen candles: Oxygen candles are chemical candles that burn and yield oxygen. In such cases, oxygen candles are usually utilized. 
• Liquid oxygen tanks: These are storage tanks for super-cooled liquid oxygen. Supplementary liquid oxygen tanks (L.O.X.) are utilized in addition to electrolytically generated oxygen. 
• Air scrubbers: Carbon dioxide and any other impurities are removed by air scrubber. With this, air can be recycled and used again.  

There are many ways through which submarines can generate oxygen, but electrolysis is widely used as the preferred method. It is a dependable method that produces oxygen while in submerged submarines.