Warhammer
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Anyone have a link to website that has info different air grades and the compressors, filters and such required to obtain that grade? Know off hand what grade of air most fire departments fill their tanks with?
Air Grades
- Thread starter Warhammer
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Here ya go. There is a table of different air quality specs on one of the pages. Scuba use is Grade E, and I'm sure it's the same for firefighters.
http://www.cleandryair.com/air_quality.htm
Neil
http://www.cleandryair.com/air_quality.htm
Neil
but you can get to the various standards from this page
http://www.lawrence-factor.com/air analysis.htm
Rick
http://www.lawrence-factor.com/air analysis.htm
Rick
Clunky, is it? Oh yeah, well MY site has a chart has a nifty chart that lets you compare various standard all at the same time. So there. ;^) Thanks Rick.
Neil
Neil
Thanks for links guys. But I'm still confused as to the grade used by fire departments. On one of the sites it lists that Grade L is used for Self Contained Breathing Apparatus (SCBA). I would think that would include fire fighter's tanks, correct? If so, is Grade L air suitable for SCUBA? Better or worse than Grade E?
I have a few friends that fill their SCUBA tanks at the local FD, so far, they're all still with us. So I assume it's ok. This would be ideal for me since the closest shop that can fill tanks on a walk-in basis is 100 miles from me. The only other shop, which is 30 miles from me, is an "open up for business only if you can find him type deal". So essentially you have to drop the tanks off and wait a day or 2 before he'll fill them.
I have a few friends that fill their SCUBA tanks at the local FD, so far, they're all still with us. So I assume it's ok. This would be ideal for me since the closest shop that can fill tanks on a walk-in basis is 100 miles from me. The only other shop, which is 30 miles from me, is an "open up for business only if you can find him type deal". So essentially you have to drop the tanks off and wait a day or 2 before he'll fill them.
The main difference I see is in the O2 content, which might be important. Type E calls for 20-22% while L calls for 19.5-23.5% if I read correctly. That's a pretty wide range, and could be significant if you're mixing nitrox with type L air. There's also some difference in the moisture content allowed. It seems like it OUGHT to be safe for sport diving depths. Maybe someone with more knowledge on this subject will chime in.
Neil
Neil
The difference between the two is that grade E is one of the only 2 that quotes a max for the total hydrocarbon, and that it also has a max CO value (grade L doesn't have a max for either - by the look of it they are unimportant for the spec.)
SO
If your local FD have a test certificate with the the CO levels and HC values and they are suitably low then fine - otherwise don't touch it with a barge pole!
Don't forget that at 30metres you are breating air at 4atm, and all the pollutants are 4 times more concentrated. I don't have the tables to hand, but I vaguely remember that a CO value of about 100 is enough to give you a headache - at 30 m on a normal value of 10 you will be breathing the equivalent of a value of 40 or so, due to the higher ppCO.
If you look at the filter stack on most diving compressors they are to remove two things, moisture (so your tank doesn't rust away to nothing) and hydrocarbons - the hydrocarbon is the more important since compressors, like car engines need decent lubrication - this is often put into the air stream as a fine mist, that then has to be filtered out at the end - obviously, the higher the working pressure of the compressor, the more important this is, and the larger the filter stack to remove the larger ammounts of oil used. modern ceramics are now used in some compressors to drastically reduce the oil required.
Off the top of my head I can't remember the effect of inhaled hydrocarbons, but I am sure it isn't pleasant! Of all the specs there - the USP spec is closest to the BS (british standard) for compressed air - Under the UK standards, the Diving spec is actually the cleanest spec (as you breath under pressure when diving).
To neil - It should have no effect if you are blending it properly - all it takes is one reading from the compressor output to know what % O2 the machine is giving you on that day! - it shouldn't change, since it is just bog standard air that is being sucked in!
HTH
Jon T
I wouldn't be using it for mixes, just air. But something that also interests me is whether or not you could use grade L air in a 02 cleaned tank without comprimising the 02 cleaning. The specs for grade E air list 5 mg/m3 as the acceptable limit for oil/particles. And oil is what 02 cleaning eliminates and the concern when mixing nitrox via the partial-pressure blending method. The specs for grade L air doesn't list an allowable value for oil/particles, it just has a ---- in the slot. So I wander if that means all oil is removed, air is pumped from a oilless compressor, or it's just a non-issue when dealing with SCBA.
Yeah, I saw that the margin for 02 content was twice as much for grade L, but it's only .5% more on the low side (19.5% vs 20%). And I don't think that an extra 1.5% of 02 would make any difference at all in the depths that I'd dive. Since even at 200 feet (well beyond my limit) the partial pressure for 23.5% is 1.66 vs 1.55 for 22% or 1.48 for 21%.
And in regards to the moisture specs, grade L air appears to me to be dryer than grade E. Whether or not it's enough to make a difference I do not know. But I guess it might could cause a bad case of dry mouth.
Seems it would also be less likely to freeze.
The Carbon Dioxide, Carbon Monoxide, Methane are all also ---'ed out for grade L air where they're 1000 ppm, 10 ppm, 25 ppm for grade E air. Again I don't know what the ---- means, but I'm almost positive that less is better in regards to them.
Where is Dr. Deco? Yo Doc...
Yeah, I saw that the margin for 02 content was twice as much for grade L, but it's only .5% more on the low side (19.5% vs 20%). And I don't think that an extra 1.5% of 02 would make any difference at all in the depths that I'd dive. Since even at 200 feet (well beyond my limit) the partial pressure for 23.5% is 1.66 vs 1.55 for 22% or 1.48 for 21%.
And in regards to the moisture specs, grade L air appears to me to be dryer than grade E. Whether or not it's enough to make a difference I do not know. But I guess it might could cause a bad case of dry mouth.
Seems it would also be less likely to freeze.The Carbon Dioxide, Carbon Monoxide, Methane are all also ---'ed out for grade L air where they're 1000 ppm, 10 ppm, 25 ppm for grade E air. Again I don't know what the ---- means, but I'm almost positive that less is better in regards to them.
Where is Dr. Deco? Yo Doc...
If you look in the grade N column for none it sais 'NONE'. I took the dashes to mean that it wasn't measured as part of the spec and could be as sky high and still pass.
I wouldn't put an O2 clean tank anywhere near a compressor that wasn't also a propperly certified for filling O2 clean tanks. My LDS just before I quit the UK spent quite a lot of money upgrading their filter stack (from the standard diving spec) to get the oil level down to as close to zero as they could, so that they could safely and confidently fill O2 clean tanks.
HTH
Jon T
Jon,
Thanks, I guess I should avoid reading spec charts! The point about the blending I was trying to make is that most people assume the air coming from their compressor is 21% O2. If you were blending and your mix came out a full 2% higher than you wanted, it'd be a pain in the butt. And you'd have to do more MATH! Thanks for the info!
Neil
Thanks, I guess I should avoid reading spec charts! The point about the blending I was trying to make is that most people assume the air coming from their compressor is 21% O2. If you were blending and your mix came out a full 2% higher than you wanted, it'd be a pain in the butt. And you'd have to do more MATH! Thanks for the info!
Neil
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