Continued Carbon Monoxide - Cozumel

[DandyDon]

Deaths & injuries are relatively rare in recreational scuba so even tho few compressors south of the US run inline CO monitors - the general feeling has seemed that tank air is generally safe enough. There is no way for the typical traveling diver to test for CO contamination since it's odorless & tasteless even in high concentrations, but some of us have been carrying testers and checking - more so since this thread: http://www.scubaboard.com/forums/ne...onoxide-tanks-cozumel.html?highlight=monoxide

I was getting 5 ppm on some tanks on Roatan in February, and we have had other reports coming from Coz since. I guess one may wonder about the anecdotal evidence with how good a recreational diver's tester is, how well we operate ours and calibrate, but yesterday we had two divers, two different brands of testers. I got readings of 7, 8, and 9; I think the other diver (whom I won't name but he may well join in here when he can) got as low as 6 on his other kit.

Today, we got 11, 12, and 14 on his! So what do you do when the boat is headed to the site already? We opted for shallower sites, then talked to the Op about talking to the main fill station again.

The Op has very little possible they can do unless they get their own compressor, while most small Ops use the main island station - but none of the compressors on the island have inline monitors to my knowledge, and I have certainly been asking around as I'd like to find a good example, even tho I'd still test my tanks anyway.

And the problem is not isolated to Cozumel, not in the least. I think this is pretty typical around the Latin American & Caribbean.

I blew my tester overboard in a clumsy accident, but the other diver & tester will be with us all week so we will continue our study - and I'll replace mine when I get home. See http://www.scubaboard.com/forums/ba...oxide-co-tank-testers.html?highlight=monoxide I'd like to press DAN to take some action but they never have, so - I dunno?

 

[jfcl01]

Have you seen anyone using the new Analox portable CO unit?

 

[DandyDon]

Have you seen anyone using the new Analox portable CO unit?

Nope, not yet. I used my Pocket CO and the other was the ToxiRAE 3 (see http://www.scubaboard.com/forums/ba...oxide-co-tank-testers.html?highlight=monoxide) on several tanks as compared to the fill station who does not test nor run an inline monitor. I do hope to hear from owners of the Analox personal CO tester.

Hehe, I have received a PM and a comment on a related thread questioning out abilities as testers, but we are among the only ones even trying to address the ignored risk. I am open to better testing ideas of course, from others who have taken actions; not open to ignoring the risk.

 

[cruisediver69]

I recently had a chance to use the new Analox tester in Cozumel a couple of weeks ago. My first tank showed a 17 but I wasn't able to confirm that reading on that tank or any of the others since the tester went bonkers. I ran the first reading while sitting at the dock and the subsequent ones while underway. I got readings that were off the wall (170+). The same weird readings happened later that week in Roatan while at the dock so I sent the tester back to Patti so she could figure out whether I am being real dense or if the tester actually had an issue.

Given some of the readings we are starting to see out of Cozumel, I wonder what the dive\no dive threshold should be. Also curious if there is some sort of established testing protocol that could\should be used. I have watched the folks diving Nitrox do their testing while underway. That doesn't give anyone a whole lot of time to react in the event bad readings occur.

DandyDon, sorry about the hijack on your trip report thread. I am still learning appropriate forum manners :depressed:

 

[DandyDon]

Oh we were underway, too late to request new tanks but then that would be a hassle too. If a tester is used correctly tho, there should be no ambient air contamination of test. My Pocket CO uses a bag of captured tank air, and the ToxiRAE 3 uses a direct hookup with 2 liters/min flow so both of those seem effective enough. I haven't used the Analox.

 

[kjvander]

cruise diver....

here are some assumptions

100 ppm exposure of CO will produce in some indiviuals flu-like symptoms (head-ache, runny nose, and sore/itchy eyes) So use this as worse case...a mild case exposure. So you wouldn't want your ppm to exceed 100 ppm while at depth.

using an assumption that the CO fraction completely replaces the o2/n2 fraction in equal portions that would give you a PCO of .0001 at depth (for the rest of you calculations you can use your own depths.)

reversing the calculations like you would for PO2 etc. at 99 feet you would be at 4atm. take .0001 and divide by 4 and your surface pco would be 0.00025 or roughly .0025%. This would translate to a surface ppm of 25 ppm.

so depending on your personal threshold of CO tolerance (certain people deal with CO better than others, as well as other factors if you a smoker or not, if you have had previous CO hits whether at home or at work, etc) you could tollerate a ppm of 25.

***Disclamer**** My math might be off for this...it's been awhile since i've had to do these kind of calculations....

All that being said...would I dive a tank with 25 ppm of CO....heck no....I would pass on that tank. But as Don and others have said...how would you know.

Air in its normal "ideal" form as about 0.1 ppm CO....compared to 780,840 ppm N2 and 209460 ppm O2...so there is some inherent CO in the gas we breath. Depending on where in the world the gas is being compressed at...it might be different.

However.....ultimately it is your safety and your health that you are dealing with.

 

[DandyDon]

Safe thresholds of CO at sea level varies as suggested, and which source you site - but 15 ppm is my personal limit for say 100 ft dive but that's not a safe suggestion, just a personal call.

Government accepted limits for scuba air...

Canada's diving CO spec for air is 5 ppm

USA with its CGA Grade E is 10 ppm

Australia is 10 ppm

Britain has the tightest CO spec at 3 ppm.
http://www.hse.gov.uk/PUBNS/dvis9.pdf

Rest of Europe is 15 ppm

Much of the world - not controlled

 

[kjvander]

Safe thresholds of CO at sea level varies as suggested, and which source you site - but 15 ppm is my personal limit for say 100 ft dive but that's not a safe suggestion, just a personal call.

Government accepted limits for scuba air...

Canada's diving CO spec for air is 5 ppm

USA with its CGA Grade E is 10 ppm

Australia is 10 ppm

Britain has the tightest CO spec at 3 ppm.
http://www.hse.gov.uk/PUBNS/dvis9.pdf

Rest of Europe is 15 ppm

Much of the world - not controlled

well....like i said...would i dive with 25ppm....nope...but then again 100ppm does give ya quite the head ache. I should have done the calculations for 50ppm which runs more inline with OSHA industry limits..

with using 50ppm at a depth of 100ft is 12.5 ppm at the surface

 

[swamp diver]

Nope, not yet. I used my Pocket CO and the other was the ToxiRAE 3 (see http://www.scubaboard.com/forums/ba...oxide-co-tank-testers.html?highlight=monoxide) on several tanks as compared to the fill station who does not test nor run an inline monitor. I do hope to hear from owners of the Analox personal CO tester.

Don as you know I have both the Pocket CO and the ToxiRae 3 and have always remained skeptical of the Pocket CO's ability to read a low CO concentration given that it is calibrated at 100 ppm plus this unit's sensor is completely unfiltered and cross reacts to lots of other gaseous compounds such as alcohols and nitric oxide. Waving a Magic Marker or Sharpie (both use alcohols as solvents) anywhere near the Pocket CO will result in a high positive reading for hours (don't try this as it could be days before the sensor will revert to zero ppm).

The fact though that you had both the Pocket CO and the ToxiRae 3 reading the same tanks and finding the same approximate range of CO in the tanks suggests these are true CO positives. The case for a positive result is much stronger when two different instruments, particularly two different brands of instruments, yield the same result.

I'm curious once those instruments were removed from the bag or tank and exposed to ambient conditions if the monitor returned to 0 ppm within a minute or so? If not and the positive reading remained 'hung up' this would indicate a cross reacting compound was involved.

I still find it difficult to accept that Merdianos would be burning compressor oil, but given it is the hottest time of year down there and I suspect they don't run any catalyst in the purifier this would not surprise me. For a while one of the most popular resorts on Roatan posted their monthly air tests on the web and one could see that the CO result was < 1 ppm during the winter, but for the 3 months in the summer the CO concentration would run 6 to 9 ppm. Having seen the compressor room at this resort with 3 compressors in a tiny room with little ventilation it was clear they were burning the lubrication oil in the hot summer months. Again there was no catalyst in the purifier (cheaper without) which would have lowered the CO to zero in most of these cases.

These data points provided over the last year by individual divers with personal CO protection devices is all very interesting and just further supports the accredited labs' finding that 5 to 8 percent of dive air samples submitted are contaminated with CO at levels > 10 ppm which is very disconcerting particularly for the older diver who will not tolerate the same amount of CO as a young diver. The frequency of contamination may even be higher in the tropics where high ambient heat, poorly ventilated compressor installations, petroleum oils in use, and catalyst often absent in the purifier create the perfect storm for CO production. Diver beware.

As more and more divers purchase personal CO protection devices we will get a much better idea of the frequency of contamination at these tropical resorts. As you said I doubt that this is a problem particular to Cozumel.

May I suggest a ToxiRae 3 or BW Gas Alert Extreme as your next unit. They both will tolerate a one metre accidental quick dunk in the water.

 

[swamp diver]

well....like i said...would i dive with 25ppm....nope...but then again 100ppm does give ya quite the head ache. I should have done the calculations for 50ppm which runs more inline with OSHA industry limits..

with using 50ppm at a depth of 100ft is 12.5 ppm at the surface

I'd use the NIOSH limit at 35 ppm or better yet the ACGIH's TLV at 25 ppm as they update their limits much more frequently based on the current science available.
25 ppm/5 ATA = 5 ppm maximum in the tank for recreational diving.