carbon monoxide in tanks - cozumel

[swamp diver]

All I can say about PADI no longer requiring any air testing is that one should be Scared Silly. :shocked2:

Just to put this in perspective as to how bad things are in the dive industry with regards to compressed air quality I had a chat last year with one of the large accredited breathing air lab directors and asked if they could give me the the CO failure rates for dive vs. fire service compressed air. One hundred percent of the fire service air sent in was from US fire halls whereas the dive air included numerous samples from offshore tropical compressors as well as the US dive shop compressors.

The CO failure rate for diver compressed air was still about 3 percent, but for fire service air it is 0.1 percent.

Why? Because fire services generally have proper installations with adequate compressor ventilation, the compressors are newer than those in the dive industry and properly maintained, the operators are trained, there are CO monitors installed, and the compressed air is tested quarterly just "before" the cartridge is due to be changed out. In the dive industry the operators game the system by changing the filters and sampling immediately afterward with a cold compressor which is the best case scenario. Even with gaming the system the dive fill stations still have a 3 percent failure rate.

With the recession and dive shops hurting for business it is pretty clear that without the PADI quarterly testing requirement many shops will just stop testing. While quartery testing was not ideal it at least raised the level of awareness as to the potential problems and showed the diver the fill station operator was meeting some sort of minimum level of quality control.

In the current environment it is truly dive beware and one must remain air aware. It is true that most jurisdictions (except Florida) have no guidelines as to how often a recreational shop should test their air quality. Vote with your credit card and only support those shops which continue to test and show an interest in your safety. Spending $300 on a portable CO monitor is really the only sure fire way to reduce this CO risk to zero on a personal basis.

 

[FastEddy]

Hopefully, as more people choose to protect themselves by using personal CO monitors prior to breathing air out of tanks, they will post their results on forums such as this, after their trips. Perhaps this will then raise awareness as to which ops are cutting corners to save a few dollars at the risk of hurting their clientele and which ops care enough not to poison the hand that feeds them.

"Vote with the credit card" (I like that).

 

[jfcl01]

to Swampdiver and DandyDon (and anyone who tests their tanks individually)

Just wondering...when you pull out your CO tester on a dive boat, do the other divers ask you to check their tanks too?

 

[swamp diver]

to Swampdiver and DandyDon (and anyone who tests their tanks individually)

Just wondering...when you pull out your CO tester on a dive boat, do the other divers ask you to check their tanks too?

Yes all the time and that is why the Pocket CO with its clumsy 3 minute in a bag sampling technique on a rocking small dive boat makes it very difficult to check other tanks. Best to do it before the boat leaves the dock.

With the ToxiRae 3 the T90 time (time to reach 90 percent of true applied concentration) is < 12 seconds and one can test about 3 tanks a minute if prepared. The BWT unit is a little slower and takes about 30 to 60 seconds a reading.

Testing other diver's tanks is a good way to increase awareness of this issue and when they see how easy it is to do most ask where to purchase a monitor.

 

[jfcl01]

Yes all the time and that is why the Pocket CO with its clumsy 3 minute in a bag sampling technique on a rocking small dive boat makes it very difficult to check other tanks. Best to do it before the boat leaves the dock.

With the ToxiRae 3 the T90 time (time to reach 90 percent of true applied concentration) is < 12 seconds and one can test about 3 tanks a minute if prepared. The BWT unit is a little slower and takes about 30 to 60 seconds a reading.

Testing other diver's tanks is a good way to increase awareness of this issue and when they see how easy it is to do most ask where to purchase a monitor.

does testing more tanks shorten the calibration interval?

 

[DandyDon]

Not me, but then I think Swampdiver's opinions are understandably more highly regarded. Some have remarked that if mine is good, then theirs must be, but that is an erroneous assumption.

 

[augustib]

Correction - PADI NO LONGER requires quarterly air sample.

Source Barry Dunford - PADI Northwest Director

Wow! this is really amazing... and just another glaring example of industry leaders ignoring the risks of bad tanks. It would be interesting to know if this requirement going away directly corresponds to the increase in diving accidents and deaths. Does anybody know when PADI changed this requirement?

 

[swamp diver]

does testing more tanks shorten the calibration interval?

No it does not. Both the Gas Alert Extreme and ToxiRae 3 are actually meant to run 8 hours a day, 5 days a week in the workplace setting. On a typical dive trip to turn the unit on for an hour a day in order to check a couple dozen tanks will not change the calibration interval.

As long as one is calibrating every 3 months if the unit is used on a regular basis it will perform reliably (accurate and precise).

I can usually tell a calibration is needed as the unit will read low when the gas of known concentration is applied before a weekend of diving. I'll accept down to 9 ppm when the 10 ppm bump gas is applied, but once the unit reads 8 ppm I will recalibrate for another 3 or 4 month interval.

The time to calibrate and ease of calibration of these units is another factor to consider.

The Pocket CO takes about 10 to 15 minutes if one follows the zero air calibration as directed.

The Gas Alert Extreme takes about 2 minutes and the ToxiRae 3 about 1 minute of gas flow in order to complete a calibration.

The newer faster sensors use less calibration gas which reduces operational costs.

It is very important to turn these units on in an area which is CO free during calibration as they do zero themselves as part of the calibration process.

 

[FastEddy]

Swampdiver:

When you test a tank with the Toxirae 3, do you first install the reg and then use a flow restricter on the low pressure BCD inflater hose to feed the air to the Toxirae 3? (so that the Toxirae is getting pure tank air fed directly into it)

If so, that is the sort of unit I am looking for, one without the plastic bag routine.

Thx.

 

[swamp diver]

Swampdiver:

When you test a tank with the Toxirae 3, do you first install the reg and then use a flow restricter on the low pressure BCD inflater hose to feed the air to the Toxirae 3? (so that the Toxirae is getting pure tank air fed directly into it)

If so, that is the sort of unit I am looking for, one without the plastic bag routine.

Thx.

Generally yes that is my standard operating protocol as most divers will have their tanks set up with a lp hose available. I pop the flow restrictor into the lp fitting and then listen at the downstream end to ensure there is air flow. Attach the black plastic fitting to the monitor and in 15 seconds the tank is analyzed. Move on to the next tank. With the Gas Alert Extreme I wait about a minute for the reading to stabilize.

See the photos below of the setup for the ToxiRae 3 and Gas Alert Extreme. You can buy extra plastic hose attachment fittings from the manufacturer. Rae Systems will sell you 10 for $35, and BWT sells one for $10 with a piece of Tygon tubing.

Alternatively if you want to check a lot of tanks quickly I have the yoke valve flow restrictor shown below from Analox which is overpriced. Better off just purchasing a DIN flow restrictor and a yoke adapter then you can do both valve types without having to attach a first stage to the tank.

The brass lp flow restrictor can be adjusted and it is set up at 1 lpm.