I found CO in tanks

[kelemvor]

I can't recall any past threads on people finding some CO in their tanks. Nor talk about CO analyzers, whereas analyzing O2% in nitrox is often discussed. To be honest, I've never given it much thought as I always get fills from very reputable shops. And you can smell it. I would think this is the norm for most divers. Is it risky to not own a CO analyzer?

I found CO in a tank from my LDS last year and posted about it. It was 1ppm. They immediately apologized, did all kinds of work on their compressor, cleaned my tanks, and refilled them.

That's how I would expect any responsible shop to handle the situation.

 

[tbone1004]

Why would you want to use this device and not get O2 fill at your local medical gas supply company? I don't see the attraction unless you are on an island without access to O2.

simple, cost, it's less than a tenth of the cost.

This is the same technology that many remote places use to generate O2 on a mass-scale, the only downside to using it is if you are in a rebreather because of the argon buildup *dil flush every 15 mins and it's a non-issue, though I don't use it for my onboard O2*, but there are no downsides to using it on open circuit.

The unit is rated for continuous operation, and combined uses about .18kwh/cf. Average electricity cost here is $0.12/kwh so it costs me just over $0.02/cf. Average O2 costs from the dive shops is $0.40/cf and I can get it about half that through work. If I did that, I would also have to have some sort of booster pump that would cost me more to run in electricity for a LP compressor than the Invacare system, plus the cost of the booster *I paid $160 for mine from a family who no longer needed it, and it came with 4 small medical bottles. I had to put about $100 into a whip but you'd have to do that for a Haskel anyway*.

 

[49north]

I am going to give the dive op the benefit of the doubt here and hope that they will do the right thing and look into this as they said. They said they service their compressor and get the air tested. I have no reason to believe that they don’t. If they are following accepted industry standards and if this is a one time occurrence, then I don’t really think they have done anything wrong.

When I bought the CO analyzer a few months ago, I was really only concerned about finding CO in countries other than Canada or the US where the standards may be low or nonexistent. This incident goes to show that you never can tell and underscores the importance of knowing the contents of your tank.

I appreciate the input so far as there is not much information on where to draw the line on CO.

 

[JohnN]

Why would you want to use this device and not get O2 fill at your local medical gas supply company? I don't see the attraction unless you are on an island without access to O2.

FWIW, industrial oxygen, medical oxygen and aviation oxygen all come out of the same tank. The difference in price is related to how traceable the tank certifications are.

I've been told by the local AirGas distributor that industrial oxygen users are the most fussy, any contamination really screws up their welds. . .

 

[tbone1004]

FWIW, industrial oxygen, medical oxygen and aviation oxygen all come out of the same tank. The difference in price is related to how traceable the tank certifications are.

I've been told by the local AirGas distributor that industrial oxygen users are the most fussy, any contamination really screws up their welds. . .

they also vacuum out the tanks several times for aviation and medical because the dewpoint requirements for aviation in particular are much lower. Come from the same tap of lOx, but the pre-fill is different

 

[JohnN]

they also vacuum out the tanks several times for aviation and medical because the dewpoint requirements for aviation in particular are much lower. Come from the same tap of lOx, but the pre-fill is different

Forgot to mention that. Thanks.

But for the differential, you could fill and flush the tank with O2 and still save money (particularly if you never drain the tank)

 

[tbone1004]

Forgot to mention that. Thanks.

But for the differential, you could fill and flush the tank with O2 and still save money (particularly if you never drain the tank)

part of the issue is the liability of selling a non-breathing gas *industrial grade*, to people that are going to be breathing it. Medical is cheaper than aviator, but you can't buy it in many states because it's prescription controlled

 

[49north]

Getting a bit off topic aren’t we?

 

[tbone1004]

Getting a bit off topic aren’t we?

yes and no. it's all still somewhat relevant to how CO may end up inside of a tank.
That said, you really should mention the shops name just so people can be aware to check. When Amigo's had a report they went through and redid everything and offered free refills to everyone who had filled their tanks there in the couple days prior to them getting told etc etc. I know if I was going to whatever shop you were at, I'd damn well want to know....

 

[2airishuman]

I can't recall any past threads on people finding some CO in their tanks. Nor talk about CO analyzers, whereas analyzing O2% in nitrox is often discussed. To be honest, I've never given it much thought as I always get fills from very reputable shops. And you can smell it. I would think this is the norm for most divers. Is it risky to not own a CO analyzer?

I don't have a CO analyzer but am in the process of setting up my own compressor and fill station. I will be continuously monitoring for CO with that setup, with an alarm, so no need to check individual cylinders.

CO is toxic, on that we can all agree. As with all toxins, the dose makes the poison, and so it's: time x concentration x pressure in bar. It accumulates over, what, 30 days or so. As a result, healthy people can tolerate a short, acute dose.

In society at large, the trend is towards dumbing down the detectors to focus remediation efforts on very high concentrations. For household CO detectors, the latest standards require detectors to display "0" for levels below 30 ppm and to alarm only above 70 ppm. Carbon monoxide detector - Wikipedia While this is at 1 bar, nonetheless, it illustrates that it is mainly the very high levels that are of concern. 400 ppm is considered non-hazardous for a brief exposure. OSHA regulations set a limit of 35 ppm for the average over an 8 hour shift for occupational exposures.

The point being that a 5-10 ppm level in a dive cylinder, even adjusted for hyperbaric exposure, is probably not something to be too concerned about.

That said, there have been fatalities, and there is the open question of the extent to which CO-contaminated breathing gas has contributed to fatalities previously categorized as "medical event." The data is thin.

Finally, there is no reason why a properly configured fill station should produce more than 1 ppm of CO. Hopcalite is highly effective in converting CO to CO2, and there should be some of it in every filter stack. Even on a Rix.