Oxygen Clean

Equipment cleaned and fitted with oxygen-compatible components so it can safely contact high concentrations of oxygen during filling or diving.

Oxygen clean describes cylinders, valves, regulators, and fill equipment that have been specially cleaned and prepared for contact with high concentrations of oxygen. Oxygen does not burn by itself, but it makes everything else burn violently: at elevated pressure and concentration, a trace of hydrocarbon grease, a rubber o-ring of the wrong material, or a particle of dust can ignite during a rapid pressurization and cause a fire or explosion inside the equipment.

Cleaning involves stripping the equipment, washing components in oxygen compatible solvents, replacing seats and o-rings with oxygen compatible materials such as Viton, and lubricating only with oxygen safe products such as Christo-Lube. A common industry practice is to require oxygen clean equipment whenever gas containing more than 40 percent oxygen will pass through it, and always for gas blending by partial pressure, where pure oxygen enters the cylinder first.

For divers this is mostly logistics, but the logistics matter. Keep nitrox or deco cylinders in oxygen service, label them clearly, and tell the fill station how they were last used, because a single fill from an oily compressor quietly ends the oxygen clean status. Cylinders in oxygen service also need periodic recleaning, and reputable stations will refuse rich fills into anything without documented service history.