O-RINGS FOR OXYGEN AND NITROX SERVICE
Viton O-rings are currently fashionable for "oxy-cleaning" regulators that will be used with nitrox or straight 02. There's a lot of debate in the tech diving community as to whether they are really necessary. I personally don't bother with them except for very high F02's, and not necessarily even then. The problem isn't that nitrile O-rings will explode in 02, or even combust - just that they are not generally considered compatible for long term exposure to 02. Actually, there's no such thing as a completely 02 compatible O-ring - all O-rings degrade in a high F02 situation. It's just that some do so faster than others. There's no question that nitrile oxidizes faster than viton, just whether the difference is enough to worry about in a regulator that will see regular servicing. Aviation practice, it's interesting to note, is to use nitrile for 02 applications. Nitrile, of course, works fine with nitrox mixes in the normal recreational diving range, and many divers use nitrile with straight 02 without problems. Since your regulators manufacturer probably designed your regulator with specific o-ring compounds in mind, why mess things up if it isn't necessary? Viton O-rings behave differently than nitrile, and there's no assurance that a generic viton O-ring will perform as well as the OEM one the engineers who designed the regulator speced for it. Many manufacturers are now offering nitrox kits. There's a lot of debate as to what the point of these are, since most of the manufacturers say they are only good for recreational nitrox mixes, and those mixes work fine with an unmodified regulator. What seems to be going on is that the liability obsessed manufacturers are selling what are actually straight-02 kits and calling them nitrox kits, figuring to make a few dollars more off the more gullible nitrox divers. Usually the rebuild kits for these "nitrox regulators" can be used on the air versions of the same regulators, making them ideal for converting air regulators for straight 02, since the components of the kits come with the blessing of the factory engineers.