Nitrox is a gas mixture that exist of nitrogen and oxygen, but in another composition then the 79%:21% of which air is composed. For diving, Nitrox mixtures are used which contain an oxygen concentration between 22% and 40%. This is known as enriched oxygen.
The advantage of diving with Nitrox is the lack of nitrogen content in the breathing mixture. And as most divers are aware, Nitrogen absorption is the main contributing factor of 'decompression sickness' or 'the bends', this is why we can only stay down for a limited period of time.
Simply by reducing the amount of Nitrogen and increasing the amount of Oxygen in a blend allows you to stay down longer as you are absorbing less Nitrogen during the dive.
For this application you can use the Parker EnOxy module range. This range of modules produce Enriched Oxygen in various purities, ranging from 28% to 40%.