nitrox 
noun [mass noun]
A mixture of oxygen and nitrogen used as a breathing gas by divers, especially a mixture containing a lower proportion of nitrogen than is normally present in air, to reduce the risk of decompression sickness.Using nitrox to reduce your nitrogen content offers these advantages....
- I later ask Terry about oxygen, nitrox and helium.
- With basic and advanced nitrox divers should not be able to buy oxygen.
Origin
1980s: from nitrogen + oxygen.