nitrox

Short definition from Wiktionary

Noun

1. 1
   An industrial process for case hardening (imparting greater surface hardness to) metal objects, involving nitrocarburizing (the diffusion of carbon and nitrogen into the metal) followed by oxidation.
2. 2
   A mixture of nitrogen and oxygen, the nitrogen content being lower than that of normal air, which is used in place of air as a breathing gas.