Gas Mixture Carried by Scuba Divers
Puzzle 6 of Deep Sea Journey Hard Pack
Question is: Gas Mixture Carried by Scuba Divers
and the answer is: NITROX
Word Meaning:
NITROX — (metallurgy) 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.
Definitions from Wiktionary.