O2 analyser is a must or not????

[RICHinNC]

My problem with buying an analyzer of my own is how often I get to dive nitrox. Unfortunately my work keeps me on the road a lot and I am lucky to get a couple of dive vacations a year. And, the analyzer thing only lasts a year and then has to be replaced. I know I described that pretty poorly...but work with me here...been a long day. So, I will use theirs...the lds...and hope it works.

ok...flame me now....

 

[double80s]

If you dive rental tanks for EAN on a regular basis, it is convenient to own your own analyzer. Once you own tanks that are being used for EAN, I feel you MUST purchase an analyzer. The cost of the analyzer vs the risk of grabbing a mislabled tank is too great.

 

[CompuDude]

My problem with buying an analyzer of my own is how often I get to dive nitrox. Unfortunately my work keeps me on the road a lot and I am lucky to get a couple of dive vacations a year. And, the analyzer thing only lasts a year and then has to be replaced. I know I described that pretty poorly...but work with me here...been a long day. So, I will use theirs...the lds...and hope it works.

ok...flame me now....

In that case, your best bet seems to be finding an LDS you feel you can trust, and ask them about the service record of their O2 sensor each time you use it to check your tanks. I trust my LDS. I still want my own sensor at some point, but I'm not sweating it.

 

[CompuDude]

You definitely should not trust the mix in any cylinder without analyzing it yourself. It is not just PADI that teaches you to analyze your own mix and to mark your name, the fraction of O2, and the maximum operating depth on the cylinder. That's what SSI (and as far as I know, every other agency) teaches. Every place I have used nitrox has the same requirements. You also enter the same information in their logbook. Any place I have used nitrox has always had an analyzer. You definitely want to calibrate it, typically off an air cylinder. I would have to think twice about using a dive op that skipped any of these steps. This is basic safety procedure for nitrox. If you don't want to spend the money on an O2 analyzer, you don't need to. If the dive op can't provide an analyzer (because it's out of order that day or whatever), you would have to use air instead of nitrox, but that sure is not the end of the world.

I was taught to calibrate it to the same air we stand around breathing. Perhaps if I wanted to carry around a cylinder I knew to be exactly 20.9%, but other than that, I wouldn't trust using someone else's random tank to be plain ol' air. Far more reliable.

I note a post a few up about varying O2 percentages with temperature and humidity, and will be discussing the matter further with my instructor, but consider the LDS I get my nitrox fills from is air conditioned and in SoCal (pretty low humidy year round), I strongly suspect they'll be right in the target range through all four seasons.

 

[Dive-aholic]

This happens to me every time I get a Nitrox tank from the LDS. They analyze the tank while it's hot as soon as they've mixed it, and put a sticker on it and rack it. I walk in and ask for xx% Nitrox. They go to the rack, pull something that's labeled as being in that range and I take it back to the analyser (the very same analyser they used when they filled it). The measurement I get is guaranteed to be off by at least 1% from their original measurement, and it's been off by as much as 3% on occasion.

The only explanation I can think of for why some people see this and others don't is that some LDS's use partial-pressure blending while other's use a membrane system. In a membrane system the mix would enter the tank at the specified blend and no mixing is required.

Edit- I'm guessing that filling tanks from banked Nitrox would also result in an accurate reading instantaneously, since the blend has mixed in the bank.

Most of my fills are PPB. I think what's happening is the LDS isn't leaving the analyzer on the tank long enough. It takes about a little bit for the analyzer to get the reading.

 

[Puffer Fish]

There is a recent DAN study of tank air quality that showed that, if i remember correctly 17% of the sample tanks they tested (independent lab) were more that 2% off (Nitrox), and that air tanks also had issues with O2 %, CO and CO2. Blending Nitrox with bad air to start with - results in bad nitro.

If you can afford it, get your own, if not find a place, if you can that has two. Not able to get that, then know when the unit was tested and how good their air quality is (any good shop should have a recent air quality test)

 

[Cacia]

Doesn't the fill station have a number that can be visualized-- like .36 which can be compared to your analyzer reading after calibration? so if it says .36 and your reading is .35999, you can be happy if there is not a big disparity?

I need to be more compliant on this...no excuses. Poor form. It is easy to get too casual about Nitrox.

 

[Puffer Fish]

Doesn't the fill station have a number that can be visualized-- like .36 which can be compared to your analyzer reading after calibration? so if it says .36 and your reading is .35999, you can be happy if there is not a big disparity?

I need to be more compliant on this...no excuses. Poor form. It is easy to get too casual about Nitrox.

The meter should read in three places, as in .364, or 36.4% (more likely), but the measurement is based on a piece of test equipment, using a sensor that is very easy to not work correctly. Just calibration, using any regular tank, will cause some of this, but over time, the sensor will not scale correctly.

There is no absolute ways to check this (for a regular person), but using two different meters is a giant leap over filling and then checking with the same tool.

I have a much more complex tool, and can measure O2, CO, CO2, N, NOx, but it is a bit big and a bit heavy to use on every tank - nice to audit the quality of air you are getting though. Actually, monthly checks with this sort of equipment should be part of any tank filling operation, but I doubt that happens very much.

 

[Dive-aholic]

There is a recent DAN study of tank air quality that showed that, if i remember correctly 17% of the sample tanks they tested (independent lab) were more that 2% off (Nitrox), and that air tanks also had issues with O2 %, CO and CO2. Blending Nitrox with bad air to start with - results in bad nitro.

If you can afford it, get your own, if not find a place, if you can that has two. Not able to get that, then know when the unit was tested and how good their air quality is (any good shop should have a recent air quality test)

Standards require fills to be within 1% of the requested blend. Like I said in a previous post, I like it a lot closer. 1% can alter my dive plan. 2% is completely unacceptable. I make them bleed off the tank and get the mix right, then I don't go back there for any more fills.

 

[PerroneFord]

Standards require fills to be within 1% of the requested blend. Like I said in a previous post, I like it a lot closer. 1% can alter my dive plan. 2% is completely unacceptable. I make them bleed off the tank and get the mix right, then I don't go back there for any more fills.

I usually give a high and low side to the operator when I get fills. If I am at my shop, I know the fill will be right. But at other shops, I'll tell the blender to give me 36% and a bit richer is ok, or give me 30% and a bit lower is ok. Depends on my dive. If I am doing a spring dive to 70ft I'll ask for 36% or a bit richer. If I am going to do somethin more deep, I give leaner number, and say if it's a bit lean that's fine.

I don't pick up pre-mixed tanks of Nitrox.