Nitrox Analyzer

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The Analox O2 analyzer is the one I have seen the most of (by far) out in the field.

I got my own Analox after a trip to Hawaii where the shop I booked through met me at the dive boat with my tanks of Nitrox. The DM that brought the tanks did not have an analyzer with him. The boat did not have an analyzer. I had to choose between diving unanalyzed tanks that were allegedly Nitrox 32, or diving other tanks that were air. I used the tanks of air. And bought my own analyzer as soon as I got home.

Sometimes, dive charter logistics mean that you don't have any opportunity to analyze your tanks until you are on the boat and have already left the dock. Analyzing your tanks is too important (to me, anyway) to RELY on the boat having a working analyzer that is in good shape. That is why my Analox is in a small, waterproof Pelican case that I can have in my dive bag when I get on the boat. When I analyze, I will use my own. If I get questionable readings or mine is dead, then I will hope the boat has one and use that. If mine was dead and the boat didn't have one that worked, I honestly don't know what I would do (besides be royally pissed).

My Analox was a shop demo model and I don't know for how long. I keep it in a small Pelican box, and with the "sensor saver" cap in it. I periodically checked calibration against pure O2, to confirm the sensor was still good and it lasted me almost 4 years. And I have no idea how old it really was when I bought it. So, it analyzed tanks for me over probably 200 - 250 dives. The replacement was a bit over $100, if I recall correctly.

I have never tested for CO. I know I should. I just have not yet gotten off my wallet and bought an analyzer for that.

But, from what I have read, the amount of CO that will hurt you is somewhat dependent on the depth you dive to and, therefore, the actual amount of CO in your lungs. At 100' there will be twice as many CO molecules in your lungs as there were when you were at 33'. Hopefully, it's just 2 times zero.

My gut is that 3 ppm is fine for any kind of normal depth (even to 200'). Over 10 and I wouldn't dive it (which begs the question of why I have not bought an analyzer yet!). Over 5 and I would only be likely to use it if the dive were going to be pretty shallow.

One thing that I *think* about the Palm O2 analyzer is that it can only be calibrated to air. I could be wrong about that. If so, somebody please correct me.

If that IS correct then that means a couple of things:

The correct calibration for atmospheric air is frequently not 20.9. Depending on barometric pressure, ambient temperature, and ambient humidity, it can be as low as maybe 20.1 (I don't have my calibration chart in front of me). For me and where I live, it's often 20.5. So, the only way to really be sure of the Palm calibration is to calibrate it using a scuba tank that is KNOWN to be air. That will (should) be perfectly dry (i.e. no humidity) air and can be used to calibrate to 20.9.

In contrast, the Analox comes with a chart so you can see what the correct value is and then calibrate to that. And, if you are going to be analyzing tanks with high O2 content (above 50%), you can calibrate the Analox to 100% using a tank that is KNOWN to be pure O2. That will then give you a (likely) more accurate reading on this high O2 gases.

How much does all of that matter for normal recreational diving (i.e. Nitrox that is 40% O2 or less)? Probably not really a whole lot. The Palm calibration might be off by 1/2 a percent or so. Given how "rough" NDL calculations are anyway, having your computer set for a mix that is 1% off from the "correct" setting is not likely to kill anyone (unless they were going to die with a correct Nitrox setting anyway) or get anyone bent.

I find all the science of this interesting, but when actually doing a dive, I don't need this level of detail.

My biggest concern is getting a tank with air or 40% when I asked for 32%. If it has 30.6% or 33%, I don't get upset about it and do the dive with my computer set to 32%.

I too, need to invest in a CO tester.
 
I find all the science of this interesting, but when actually doing a dive, I don't need this level of detail.

My biggest concern is getting a tank with air or 40% when I asked for 32%. If it has 30.6% or 33%, I don't get upset about it and do the dive with my computer set to 32%.

I too, need to invest in a CO tester.

Understood. The issue with the science, though, is that if you don’t understand and test for it, you could end up with an analyzer that calibrates to air, but then tells you that you have 32% when you actually have 40%. Or even 100%.
 
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I bought an Oxycheq Expedition O2 analyzer in early 2007, and it has been great. The sensors run around $85 and are easily replaced. My sensors have lasted from 18 to 36 months.

I won an Oxcheq CO analyzer in late 2011. Had I not won it, I would have purchased one because a friend/buddy died from CO poisoning about a month earlier. Also, I had another friend who got a bad fill with CO which was detected when he analyzed the tank. (The dive shop took immediate action to correct the issue, made it right with my buddy, and contacted others who had gotten a fill). I even had an O2 fill that was in the 7 parts range Seems like the first sensor lasted 5 years, and I have had the second sensor for abut 3 1/2 years. The current price is $140, and I would pay extra to have Oxycheq replace it and calibrate it.

I keep a sensor saver on both but only to keep from spilling something in them. When I have to replace either analyzer, it will be the same thing. I like having my own so I know one is available to analyze my tanks when I want to. Normally that is not when I get a fill because I am ready to get home. Also, I know they have been cared for, batteries changed, etc - kind of like owning my own regs and BC,
 
i did my nitrox cert and think i dove 2 tanks which i saw analyzed before i bought my own analyzer.
its a worthy investment, i have my own compressor but before I brought in 02 i didnt analyze anything since i was incapable of anything but air, as soon as 02 came i analyze every single tank regardless. Im not letting a " i was busy and half paying attention" be the reasoning for the end of my life.

that said i occasionally fill tanks for buddies and it blows my mind not once has a single one of them has ever asked to analyze them or see it done or see a pic, from air to rec nitrox to deco gases to o2.
its cheap piece of mind to do it yourself dont think they will be insulted. Id never be insulted for someone to analyze and Id never forgive myself if i gave them a different mix than i told them and something happened.
 
I thought that I'd add my 2cents regarding Carbon monoxide testers as I just spoke with a sales rep for "Sensorcon". Made in the USA and it's waterproof. Their unit was not really designed for the SCUBA crowd but they have been receiving many inquiries from us. They said the unit could be used by either inserting a hose at the sensor intake or by filling a zip-lock bag with air from the tank you're testing and placing the sensor unit inside. (I'd choose this method so I didn't over-pressure the sensor). Other divers have reported good results with this method. The Rep also gave a 20% discount for purchase from their web-site... use "scuba20". $103 and free shipping. I'll report back once it gets here. Did I mention Made in the USA and NOT China? (sorry...that's big with me lately.)
 
it's waterproof.
Yep, I ran one thru a complete washing machine cycle. It was fine.

inserting a hose at the sensor intake
That approach can overpressure the sensor giving a false positive.

filling a zip-lock bag with air from the tank you're testing and placing the sensor unit inside.
That's the method I use, but turn the unit on (I leave mine on) and put it in the bag first. Squeeze all of the air out of the bag and crack the tank valve before putting the bag over as some valves will suddenly open so wide as to shoot the bag off of the boat (I know!) I use gallon bags with the handles for fasting closing and carry a new bag each day as they develop leaks. You may well suck some ambient air in as you add tank air that could taint your test, but it will be you an idea as to whether the tank is safe or not.
 
While we're on the topic.... I attended the DAN seminar at DEMA regarding Quality Assurance of Breathing Gases and carbon monoxide became a little bit more interesting to me. The presenter was Francois Burman who mentioned Nitrox blending using a membrane system which takes air and removes the nitrogen. The oxygen (and a little of everything else) is then blended with air, fed into the compressor and produces the Nitrox. His point was the membrane doesn't remove the CO. It takes about 5 liters of air to make 1 liter of oxygen, so a small amount of CO becomes 5 times that in the O2. It gets diluted in the mix but presumably with the same contaminated air....now take that down to the MOD for the Nitrox and it's easy to see that we might have a problem. Certainly, a well maintained system with current filter stacks will address the problem, but how about that dive in a far away paradise with questionable facilities?

Anyway, that's why I'm interested. Oh, and if I've got this all wrong, please tell me and we can both point the finger at Francois.
 
While we're on the topic.... I attended the DAN seminar at DEMA regarding Quality Assurance of Breathing Gases and carbon monoxide became a little bit more interesting to me. The presenter was Francois Burman who mentioned Nitrox blending using a membrane system which takes air and removes the nitrogen. The oxygen (and a little of everything else) is then blended with air, fed into the compressor and produces the Nitrox. His point was the membrane doesn't remove the CO. It takes about 5 liters of air to make 1 liter of oxygen, so a small amount of CO becomes 5 times that in the O2. It gets diluted in the mix but presumably with the same contaminated air....now take that down to the MOD for the Nitrox and it's easy to see that we might have a problem. Certainly, a well maintained system with current filter stacks will address the problem, but how about that dive in a far away paradise with questionable facilities?

Anyway, that's why I'm interested. Oh, and if I've got this all wrong, please tell me and we can both point the finger at Francois.

I'm not sure that's a complete solution? I mean, if they have their air intake near a window and a car is idling outside, the well maintained system with current filter stacks is still going to hoover in the CO and pump it into your tank, right?
 
I thought that I'd add my 2cents regarding Carbon monoxide testers as I just spoke with a sales rep for "Sensorcon". Made in the USA and it's waterproof. Their unit was not really designed for the SCUBA crowd but they have been receiving many inquiries from us. They said the unit could be used by either inserting a hose at the sensor intake or by filling a zip-lock bag with air from the tank you're testing and placing the sensor unit inside. (I'd choose this method so I didn't over-pressure the sensor). Other divers have reported good results with this method. The Rep also gave a 20% discount for purchase from their web-site... use "scuba20". $103 and free shipping. I'll report back once it gets here. Did I mention Made in the USA and NOT China? (sorry...that's big with me lately.)

Links are always helpful to the people who are interested in what you're talking about. Including one link could save hundreds of people each doing their own web searches.
 
I have an Analyox O2EII Pro with the low pressure inflater adapter. I keep the cap on it when not in use and stored in a dedicated Pelican case. I'm on 3 years with readings I consider accurate (i test on both air and O2 tanks on every trip).

I originally purchased it as the place I would visit 3-4 times a year was notorious for having poorly serviced analyzers on the boats. Convenience was a factor as well. The low pressure adapter is especially nice.
 
https://www.shearwater.com/products/perdix-ai/

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