mossym:
nope, you can put air in nitrox claen tanks as long as it is clean enough, grade e i believe
Just as a general guideline, anytime you have to qualify an answer with "I believe," you should probably be asking a question instead of making a statement, don't you think? This stuff can be dangerous and, in this instance, you're mistaken.
Grade "E" air is basic scuba air and should never be used in an oxygen clean cylinder - the permissible hydrocarbon content is too high and you can build up a residue of gunk that can catch fire when exposed to high pressure concentrations of high oxygen content gas. Modified Grade "E" (sometimes referred to as "hyperfiltered") air isn't an official standard, as defined by anybody other than the scuba industry, but it's well-known, nonetheless, and is generally considered to be acceptable for mixing with oxygen.
CGA Grade E Air Standard ("Filtered" Air)
For Filling Compressed Gas Containers Using Air.
Oxygen: 20% to 22% (balance of gas predominantly nitrogen)
Water vapor: May vary depending on intended use
Condensed hydrocarbons: 5 mg/m 3
Gaseous hydrocarbons (methane): 25 ppm
Carbon monoxide: 10 ppm
Carbon dioxide: 1000 ppm
Odor: none
Sampling Frequency: Quarterly
Lab Analysis: Recommended
NAUI Modified CGA Grade E Air Standard ("Hyperfiltered" Air)
For Filling Compressed Gas Containers Using Air to Produce Nitrox or Oxygen-Enriched Gas Mixtures.
Oxygen: 20% to 22% (balance of gas predominantly nitrogen)
Water vapor:128 ppm (v/v) -40 ºF Dew Point
Condensed hydrocarbons: 0.1 mg/m 3
Gaseous hydrocarbons (methane): 25 ppm
Solid particulate: none >2µm
Carbon monoxide: 2 ppm
Carbon dioxide: 500 ppm
Odor: none
Sampling Frequency: Quarterly
Lab Analysis: Recommended
In my experience, which is to say I've got nothing to base this on other than a lot of training and experience diving and mixing scuba gases, regulators used in recreational nitrox do not need to be oxygen serviced or cleaned. So long as you never expose them to concentrations above 40%, you won't need to worry about fire in your regulator. It's hard to criticize those who want to err on the side of caution and use O2 compatible regulators that have been maintained for oxygen service, though.
If you are using O2 concentrations above 40%, you should have your regulators oxygen serviced and cleaned and you should never use them with mixes that aren't "hyperfiltered." I clearly mark mine and reserve them for use with EAN50 and pure oxygen mixes used for decompression.
Cylinders are different, due to mixing requirements. If you are buying "premix" nitrox in concentrations up to EAN40, no special cleaning or servicing is required. Slap that Nitrox sticker on your tank (or not) and you're ready to go. If, however, you will be partial pressure blending mixes in your cylinder or using them for mixes higher than EAN40, you need to have the tank and valve oxygen serviced and cleaned. Once this is done, you should only use hyperfiltered mixes in the tank and NEVER fill it with Grade "E" air.
My personal standard is that oxygen service and cleaning expires after one year and needs to be redone annually. Expensive, but I've seen what valves and first stages look like after oxygen fires - scary stuff.
As to Ti regulators, I wouldn't use them in mixes above normox, but I'm of the opinion that they are little more than an expensive marketing gimmick and find myself wondering how anybody gets...manipulated...into buying one in the first place.
