pufferfish
Contributor
Warren_L:Steve, I think you misunderstand what I am saying - look at the Z180.1 standard. Fill stations that conform to Z180.1 and have regular testing I would consider to be clean air, but the standard still allows for 1 mg/cubic meter of oil/particulates and still be considered clean (IANTD allows for 0.1 mg/m3). My supposition is that depending on the type of oil/particulates that makes it O2 compatible or not.
I never said that bad lubricants are not a bad air problem - I believe in high enough concentrations they are. But in the amounts allowed by the standard, according to the standard, they are not.
Warren I don't think the type of compressor lubricant has any bearing on whether the air is oxygen compatible (OCA) or not other than I suppose one might be more likely to have problems with the non-synthetic oil (mineral oil) IF the fill station manager doesn't change the oil at the prescribed interval which is more frequent with the mineral oil than synthetic. The mineral oil also has a lower operating temperature so if you are running the compressor on those days here with temps in the low thirties and the compressor is in a small space with poor ventilation sucking air through a thirty foot, two inch intake 'straw' you will be more likely to get persisant vaporization of the oil or worse some silent combustion of the lubricating oil with CO production. Basically mineral oil is cheaper but requires more freqent changes which don't always get done.
The particulates can come from two sources. One is smog, pollens, dust, etc. entrained in the intake air. Particulates less than 10 microns have been identified as having both cardiac and respiratory effects especially the fine portion. Remember with any of the contaminants their toxic effects follow the same partial pressure rules as the other gas components. Message here is don't bank air on smog alert days. The other source of particulates comes within the compressor and can be from oil leaking around bad piston rings or filter media that has escaped into the air stream,etc.
OCA air is basically air where the oil and particulates, CO2, and CO allowable maximums have been lowered. Oil and partics because of the explosion hazard and CO2 as elevated levels of CO2 dilate the cerebral arteries and raise not only the risk of ox tox but also potentiates CO toxicity.
Actually what is OCA air depends on who you talk to and there is a Navy, IANTD, and ANDI standard but they are all quite close with regard to the above contaminants.
Oil and partics .1 mg/m3
CO2 500 ppm
CO 2 ppm
With our Canadian CSA Z180.1 standard you may or may not have OCA air. You will have to check the cert itself for the above three contaminant levels as CSA allows 1 mg/m3 of oil and partics and 5 ppm CO. The CO2 allowed level is the same.
I don't want to get into another raging debate of air quality standards suffice it to say the quality of air in Ontario probably ranges from 'Perrier to Walkerton' depending where you are. If a shop is only testing once a year using an unaccredited lab then buyer beware. There are just too many things to go wrong with a compressor or filtration to assume that yearly testing is of any use to the diver.
As far as where to get your Nitrox around the GTA I don't think there are many options to begin with. I'd scratch off any shop that is only testing annually or is using an unaccredited lab. Then look for ones testing to the current CSA Z180.1-00 standard. That should knock off a few more shops. If the cert is more than six months old a few more shops can be eliminated. Figuring out the two remaining shops is not very difficult.
Here is a good link on some of this stuff from Global. It is a bit dated and the CO2 should be listed as 500 ppm.
http://www.gmcscuba.com/engineering_nitrox.htm
OCA air is also known as 'modified Grade E' as shown on this NAUI page.
http://www.naui.org/ethics/NAUIAffiliateCodeOfEthics.html#GradeE