Nitrox analyzer: to take or not to take?

[Jake]

How much do you all trust the nitrox analyzers that dive ops around the world make available?

I usually work against a conservative PPO2 of 1.2 so the mix would have to be a number of points off before I'm in real trouble, but I would have no way of knowing how wrong it is.

So far my international nitrox travel has been Mexico and the Caribbean, but I'm looking at Truk and a few other places in the next few years.

I'm heading to the Cayman Islands next month for a lot of nitrox diving and got to thinking about this and the unlikely possibility of a Black Friday sale on an analyzer.

Anyone worry about this kind of thing?

(P.s. as usual, sorry if this has been discussed; you know searching can be here sometimes.)

 

[JohnN]

 

[Jake]

LMAO. Basically.

 

[doctormike]

I usually work against a conservative PPO2 of 1.2 so the mix would have to be a number of points off before I'm in real trouble, but I would have no way of knowing how wrong it is.

Remember, it's not just your MOD and OxTox that can be an issue with an analyzer error. If it is reading high, then that puts you at risk for DCS, since the mix isn't as rich as you think it is.

That having been said, I think that the ones at dive shops are probably OK - I have an analyzer but I don't travel with it. Those sensors work the same way as rebreather sensors, but they wear out MUCH more slowly since they are usually only exposed to a PO2 in the .32 - .36 range for a few seconds at a time (as opposed to 1.3 for hours at a time). Unless the shop does a lot of CCR or tech business, they probably never read over .36.

I'm not an expert on this at all, maybe someone else can chime in, but IIRC the most common failure mode is current limiting, which is generally not a problem at such low PO2s. It is less common for the sensors to become non-linear in the lower range, or to leak electrolytes due to physical damage or manufacturing problems.

 

[lermontov]

How much do you all trust the nitrox analyzers that dive ops around the world make available?

I usually work against a conservative PPO2 of 1.2 so the mix would have to be a number of points off before I'm in real trouble, but I would have no way of knowing how wrong it is.

So far my international nitrox travel has been Mexico and the Caribbean, but I'm looking at Truk and a few other places in the next few years.

I'm heading to the Cayman Islands next month for a lot of nitrox diving and got to thinking about this and the unlikely possibility of a Black Friday sale on an analyzer.

Anyone worry about this kind of thing?

(P.s. as usual, sorry if this has been discussed; you know searching can be here sometimes.)

well im assuming you l have to check and sign for your nitrox? so its already been checked at blending and then again at signing with a different analyser - id think thats enough

 

[OzMikeM]

Here is my experience.

I was at Blue Lagoon Resort Truk Lagoon in September 2018. They had 2 analysers in the fill room for guests to use, for the week I was there only 1 worked. It got an absolute hammering. With 30+ divers the device was testing 80+ tanks a day. People treat this gear like it's not their own so I saw the analyser get dropped at least once and used with wet hands, wet gear, wet tanks multiple times.

The drill at Truk is they fill your tanks in the fill room and leave them there for you to analyse and mark before they cart them to the dive boat for you. So everyone was using the shop analyser to check there fill. I had my analyser on the boat in my drybag. I would double check my fills on the boat as I have a BCD inflator hose attachment that makes it super quick to do.

The first couple of days we were diving the standard banked 30% EAN. Each time I analysed the tank with the shop analyser I was getting 28-29%. I checked it a few times with my analyser and it read 30%. So only a minor variance. I set my DC to 29%.

On day 3 we lined our selves up for some deco diving so our group requested air in back gas and stages with 50% and 100%. The shop analyser on my stages read 48% and 90% respectively. My analyser said 50% and 98%. This was consistent for the next 4 days of deco diving.

So as per @doctormike at the low end of the EAN range = minor variance, top end = high variance.

That should help you with your decision.

Mike

 

[KenGordon]

I have met a couple of broken ones. I always take my own.

Keep on top of it though. If you are not actively using it how do you know it is still ok?

 

[Kharon]

In my class we were taught that we had to calibrate the analyser before checking the tank. Wouldn't that make a second analyser moot?

 

[jstrang]

I always take my own.

I would be careful presuming places can deliver 100% O2, Truk for example has an oxygen generation plant - but it generally is limited to 95-96% O2. For CCR divers they should adjust the calibration setting for the O2%.

The O2 cell will start to read low when it is getting old. Nothing like a reading of 0% O2 when on room air to remind you it is time to change the cell. IME the cell lasts 2 years or so. YMMV.

 

[Johnoly]

How much do you all trust ......

You hit the key controversial issue on your 1st statement. TRUST . There are just different levels of trust (fillers/compressors/sensors/etc) with divers and that's what starts all the disagreements on how much trust in analyzing tanks. The accidents section of this board are littered with dead divers who trusted someone else. But it won't happen to you.....maybe.

P.S. I test every tank for O2 & CO with my own equipment or I don't dive it. Been burned so many times before.