james croft
Contributor
But he will charge you for a nitrox fill.DennisW:
Filling Air into a "Nitrox" Tank ILLEGAL?
- Thread starter Steve Lawson
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fppf
Contributor
daniel f aleman:
Thanks for the links, talk about hitting your own horn with the PSI standards. As far as I understood, DOT is the only real LAW set in the states. The other standards are industrial guidlines. When you get a tank Hydroed it is a DOT approved station that does it.
You took the fill express quote totally out of context though. In that part they are talking about cylinders that are permently marked with a MOD or Fill, here is the rest of it....
"Filling a cylinder with a breathing gas other than is labeled can create dangerous situations where the contents might be used under the assumption it's actual contents match the labeling. If a cylinder has been dedicated to a specific breathing gas with permanent MOD or contents labels, we will fill that cylinder only with the labeled gas. For example, if the cylinder is labeled "Oxygen 20 ft" we will fill only with 100% Oxygen or if the cylinder is labeled with "70" maximum operating depth we will fill only with 50% Oxygen. If you wish a fill with other than the permanent contents label, the label must be removed or obscured (i.e. covered with tape)."
If you read down the page, here is the true policy....
"Will you fill my Nitrox cylinder with Air?
Yes. We can fill your Nitrox cylinder with Normoxic Nitrox (also known as Oxygen-Compatible Air). This means we will follow our policies and procedures as for any other Nitrox mixture: the cylinder contents must be analyzed and a contents label affixed to the cylinder. The price for the fill is the same as for our Nitrox sport premix."
The only real problem with filling a Nitrox tank with air is the air must be ultra pure. This is to keep the oxygen compatability of the tank, IE keep it clean. I have air put in a Nitrox tank all the time, almost all my tanks are O2 cleaned. I just check them and write 21% MOD 187 on them.
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He's not crazy, but he's not exactly right either.
There are any number of valid reasons that they might not fill a nitrox tank:
There are any number of valid reasons that they might not fill a nitrox tank:
- Your tank is marked O2 clean and they don't have O2-compatible air. Filling the tank might contaminate it, making it no longer O2 clean.
- They may not be setup to analyze nitrox tanks and have a problem letting a tank containing an unknown mix out of the store.
- Their insurance company may be preventing them from filling anything exept plain air.
- He isn't certified to fill anything except air.
Steve Lawson:
fppf's post is well stated. I do the same thing marking wise with a deco bottle that gets put into occasional pony bottle service - it reads 21% with a 187 ft MOD when fill with oxygen compatible air.
The logic of not filling a dedicated EAN cylinder with plain old grade E air makes sense as compressed air can meet grade E standards and still have an excessive amount of hydrocarbons in it to be O2 compatible. If a fill were done with Grade E air containing excessive hydro carbons it could result in contamination in the tank that could make it unsafe for future partial pressure nitrox fills.
Where the no air in nitrox tanks logic runs off the rails however is in the failure to recognize that just about every shop on the planet that mixes nitrox through either partial pressire or membrane techniques already uses the additonal filtering needed to ensure all their air meets the lower hydro carbon standards required for O2 compatibility. To do otherwise is just inviting cross contamination issues.
Consequently, it is not at all unreasonable to expect what amounts to a "21% Nitrox" fill at a shop that sells nitrox. A "21% Nitrox" fill also should not cost more than an "Air" fill from the same shop. The additional cost for Nitrox comes from the cost of introducing the additional oxygen, not from the minimal cost of the additional filtering which is most likely already being done to their regular "air".
One thing that is also seldom considered is that while O2 compatible air has less hydro carbons, it does not have zero hydrocarbons in it. Consequently, I am less concerned about a tank that has had a few fills of grade E air with an excess of hydro carbons (but still within reasonable grade E limits) than I am about a heavily used nitrox tank that has had perhaps 100 nitrox fills with the lower (but still present) hydrocarbon limit. The potential for hydrocarbons to accummulate on the interior surface of the tank to unsafe levels is much greater in the second case than in the first.
The irony here is that you will be most likely to find these heavily used tanks in the rental racks at the same dive shops that do nitrox fills and most would not hesitate to do a partial pressure nitrox fill on this potentially contaminated tank as the tank has been religiously filled with nitrox compatible air in the past and is not viewed as being potentially contaminated.
I get worried any time strict adherence to the rules becomes more important than knowledge and common sense.
The logic of not filling a dedicated EAN cylinder with plain old grade E air makes sense as compressed air can meet grade E standards and still have an excessive amount of hydrocarbons in it to be O2 compatible. If a fill were done with Grade E air containing excessive hydro carbons it could result in contamination in the tank that could make it unsafe for future partial pressure nitrox fills.
Where the no air in nitrox tanks logic runs off the rails however is in the failure to recognize that just about every shop on the planet that mixes nitrox through either partial pressire or membrane techniques already uses the additonal filtering needed to ensure all their air meets the lower hydro carbon standards required for O2 compatibility. To do otherwise is just inviting cross contamination issues.
Consequently, it is not at all unreasonable to expect what amounts to a "21% Nitrox" fill at a shop that sells nitrox. A "21% Nitrox" fill also should not cost more than an "Air" fill from the same shop. The additional cost for Nitrox comes from the cost of introducing the additional oxygen, not from the minimal cost of the additional filtering which is most likely already being done to their regular "air".
One thing that is also seldom considered is that while O2 compatible air has less hydro carbons, it does not have zero hydrocarbons in it. Consequently, I am less concerned about a tank that has had a few fills of grade E air with an excess of hydro carbons (but still within reasonable grade E limits) than I am about a heavily used nitrox tank that has had perhaps 100 nitrox fills with the lower (but still present) hydrocarbon limit. The potential for hydrocarbons to accummulate on the interior surface of the tank to unsafe levels is much greater in the second case than in the first.
The irony here is that you will be most likely to find these heavily used tanks in the rental racks at the same dive shops that do nitrox fills and most would not hesitate to do a partial pressure nitrox fill on this potentially contaminated tank as the tank has been religiously filled with nitrox compatible air in the past and is not viewed as being potentially contaminated.
I get worried any time strict adherence to the rules becomes more important than knowledge and common sense.
Scared Silly
Contributor
I think term illegal is a bit muddied. However, this is probably the best way to get the point across to the vast majority of people. The reason I say muddied is because the standards for labeling are from the CGA which is an industry standard this is not part of the CFRs. Although the CFR could reference them which that case they are basically defacto "the law'. Note I say could be because I have not read through all them as it pertains to cylinders.
Hopefully I will state this correctly. But there are also the shops that do continuous mixing which does not require O2 Compatible Air. As such, this is where the Nitrox Compatiable vs O2 Clean comes in.
Perhaps another way of thinking is just because a cylinder is O2 clean does mean it is always O2 clean.
DA Aquamaster:
Hopefully I will state this correctly. But there are also the shops that do continuous mixing which does not require O2 Compatible Air. As such, this is where the Nitrox Compatiable vs O2 Clean comes in.
DA Aquamaster:
Perhaps another way of thinking is just because a cylinder is O2 clean does mean it is always O2 clean.
Who cares, if it's backgas? The op was talking about his doubles - not a dedicated high % o2 bottle. You're not gonna' get more than 40% at a chain LDS like S.C. anyway. Labels, shambels. Just give me what I ask for - it's my tanks, and I doubt I'll blow up your shop with my 32%. You wanna' analyze my remaining gas to make sure I'm not doing the partial pressure fox trot on you, ok (although, you might get a 0% reading 
).
Really, until you get over the 50% hump, just give me the gas.
).Really, until you get over the 50% hump, just give me the gas.
Gil57usa
Contributor
It really is amazing where some people get their information. It is the DOT that regulates compressed gas cylinders. OSHA is also involved in one way or another. Rest assured though, it is not illegal to fill a nitrox tank with air unless it is permanently marked as a nitrox tank in some way.
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he's misguided
Steve Lawson:
lamont
Contributor
Steve Lawson:
Yup, if you think the fillmonkey was doing anything remotely according to any policy or rational safety practice that DOT/PSI/etc recommend read that sentence over again.
I'm pretty sure that I've read about the Sport Chalet on this board before as well -- if memory serves they partial pressure blend nitrox, but it'll take you a serious argument to get them to top a nitrox-labelled tank with EAN21...
Could someone please direct me to whatever statute makes putting air in a nitrox tank illegal. I am not familiar with US laws.
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