The term oxygen service generally means using pure oxygen
(oxygen concentrations of 95% to 100%), but the term is sometimes used
more broadly to refer to any gas mixture containing more oxygen than
air. The "standard air" we breathe is composed of 20.95% oxygen, 78.05%
nitrogen and 1% of trace amounts of other gases, including argon, carbon
dioxide, neon, helium, krypton and xenon (the amounts vary depending
upon your geographical location, altitude, etc.). For practical
purposes, most technical literature rounds off these percentages and
defines "standard air" as 21% oxygen and 79% nitrogen.
Oxygen mixture generally refers to gas blends containing between 50% and 95% oxygen.
Oxygen - enriched air, nitrox , and enriched-air nitrox (EAN)
are generally used synonymously in the diving industry since all refer
to pressurized diving gas mixtures containing various oxygen
concentrations greater than standard air. For example, two common
mixtures used by divers are EAN 32 (32% oxygen) and EAN 36 (36% oxygen).
However, in the gas industry, oxygen-enriched air is sometimes
defined more specifically as gas mixtures containing more oxygen than
found in standard air, but no more than 50% oxygen.
To avoid confusion, Luxfer prefers using the term oxygen service to refer only to pure oxygen usage and enriched-air nitrox (EAN) to refer to oxygen-enriched breathing mixtures used for diving.
Whatever term you choose, the main thing to remember
concerning Luxfer scuba cylinders is that when you fill a cylinder with
an oxygen concentration of 23.5% or more, that cylinder must be
specially cleaned for oxygen service as though it contained 100% oxygen.