Sources of CO in compressed air

[DandyDon]

Of all the hundreds of divers I have been and are friends with, I have never heard once of someone getting CO or knowing of someone who got CO in a tank.

Until I read Scubaboard, I had never actually heard of anyone getting CO in a tank apart from being sucked in from a petrol engine exhaust.

In many cases, ill divers assumed other causes, i.e. tainted water, tainted food, dehydration, heat exhaustion, hang overs, etc. Economical and accurate technologies for testing air are fairly recent developments, but still - many of them didn't know to test if they could, and testing divers alive or dead requires even fancier & pricier equipment. I say "many" because without testing & studies, we can only guess. Testing every tank can get boring as long as one keeps getting zeroes, but the first time I saw 3 ppm got my interest, and the first time I turned a boat for over 10 ppm impressed my previously doubtful dive bud so much he nominated me for the DAN Rolex. :laughing: Well, it was nice to hear from Dan Orr even tho we both knew I wasn't a contender. We'd talked before, about CO, and he was courteous - but not helpful.

Packing a room CO alarm is good sense as almost all hotels have water heaters and most room heaters, some of which have killed guests, and packing a CO tester for tanks is good sense because all you can do is hope otherwise. I wish I could find a small alarm I could wear everywhere, but the one I tried had too many problems.

I guess the inline analyzer is great, but it doesn't "fix" bad air. If nobody is checking the CO monitor, then it's perfectly plausible that you could get a raunchy fill...

Yep, even after we got one installed at the biggest fill station on Cozumel, there were still problems. I just keep testing my tanks.

 

[grf88]

I have just returned from a trip to the Caribbean and I am really glad that I took my Analox CO analyzer there. The resort has always provided clean air and just recently installed a new compressor and bought new steel tanks. First day of diving I tested my own tank and as expected it read 0 ppm. I gave the analyzer to my son to test his own tank. He called out and said his tank was reading 75 ppm so I assumed he had done something wrong and upset the calibration. I re-calibrated it to ambient air and then went to show him what he did wrong. Meter read 81 ppm which I thought was damned near impossible so I tested my own tank again and every other tank that was set up for the divers. Sure enough none of the other tanks registered more than 1 ppm. Tested my son's tank yet again and it still read 81 ppm, replaced his tank with a new one and set the contaminated tank to drain. When the interior of the tank was inspected they found 3" of seawater and a great deal of rust, somehow the tank had drained and had must of taken on seawater when being swum in from the boat. Hate to think of what would have happened if my son had used the tank. It also goes to show that an inline tester on the compressor would not have prevented this incident. I have vowed to test every tank that I, my son or my dive buddies dives regardless of the reliability of the source. I am sure that the other divers that were present will be in the market for an CO analyzer.

 

[kelemvor]

I've pretty much stopped testing air from my usual fill stations (sunshine scuba and Cave Country). The local aquarium I dive at just bought their own compressor and it's a really old one from some fire department. You know I'll be testing those tanks for a while!

How often does a CO meter need to be replaced (I have the analox meter)? I've never measured any CO from any source I've tested. I guess the prudent thing to do is buy "bump gas" and make sure the thing really works.

Edit: CO bump gas seems to be hard to find. Anyone know where to buy a bottle cheaper than the $35 Granger is asking?

 

[DandyDon]

81 ppm?! Wow! That would have been rough with pressure increasing on a dive. I didn't know that rust could do that, but does go to show - got to check every tank, every dive...!!

I've pretty much stopped testing air from my usual fill stations (sunshine scuba and Cave Country). The local aquarium I dive at just bought their own compressor and it's a really old one from some fire department. You know I'll be testing those tanks for a while!

How often does a CO meter need to be replaced (I have the analox meter)? I've never measured any CO from any source I've tested. I guess the prudent thing to do is buy "bump gas" and make sure the thing really works.

It gets boring checking every tank when nothing shows up, I know - until you get your first significant reading! No, you don't need bump gas, but are supposed to ensure it's working every day as covered in the manual. Just turn on, calibrate, remove the flow restrictor, and blow in it. Non-smokers will register a small change, or get a smoker (not smoking at the time) to blow in it for a bigger change.

 

[grf88]

My source of bump gas is a vintage tank that I bought that still had air in it from 1969. It reads 17 ppm and I plan on keeping it for that use until it is finally drained. Not sure if the source of the CO was from it's original fill or from rusting in the tank and will not know until it's use as a bump gas is finished.

 

[DandyDon]

My source of bump gas is a vintage tank that I bought that still had air in it from 1969. It reads 17 ppm and I plan on keeping it for that use until it is finally drained. Not sure if the source of the CO was from it's original fill or from rusting in the tank and will not know until it's use as a bump gas is finished.

Interesting. Hope it is well marked as not safe for use. Can't fly with it tho, and you're supposed to check it daily, so try my described method.

 

[grf88]

Interesting. Hope it is well marked as not safe for use. Can't fly with it tho, and you're supposed to check it daily, so try my described method.

I already do that but use the bump gas periodically to see if the readings are stable.

 

[abnfrog]

My source of bump gas is a vintage tank that I bought that still had air in it from 1969. It reads 17 ppm and I plan on keeping it for that use until it is finally drained. Not sure if the source of the CO was from it's original fill or from rusting in the tank and will not know until it's use as a bump gas is finished.

using a old tank with contaminated gas is just ludicrous ....dreager sells KNOWN bump gas ....just what id expect from you ...im glad you caught the bad gas for your son , otherwise it might have been another canadian sub aqua accident as dandy don said not the best idea using old gas and not a commercial one ...oh well at least you save about 20 bucks

 

[DandyDon]

Now, I didn't say that, did I? I wish I could find a small tank of 15 to 20 ppm CO to use as a cal-gas for $20, that doesn't require a special reg or anything else.

 

[swamp diver]

My source of bump gas is a vintage tank that I bought that still had air in it from 1969. It reads 17 ppm and I plan on keeping it for that use until it is finally drained. Not sure if the source of the CO was from it's original fill or from rusting in the tank and will not know until it's use as a bump gas is finished.

Check the % oxygen in that tank and I think you'll find it is hypoxic. If it is a steel tank I suspect it is from oxidation of the walls over time.

That is an interesting story about your son getting a tank with CO due to the rusting process. I have seen that as well in a set of steel tanks where there was an ingress of salt water. After two weeks there was about 20 ppm of CO if I recall but more importantly the air had become hypoxic as oxygen was consumed in the rusting process.