Dry cave bad air

[cerich]

One alternative would be to take a lighter in a dry bag and then simply see if it ignites and compare the flame to its open air magnitude.

great test for Oxygen...when i was on submarines when the O2 was low we couldn't use our zippos to light up, used the toaster instead.

Also a cool blue test for methane...that could be illuminating.

[syntaxerrorsix]

It shouldn't be hard at all, right?? You know what you've got in your tank....you can calibrate based off of your tank contents (obviously known) and then proceed. I know some analyzers are locked in to the mode of "zeroing" to Air, but the Oxycheq unit would let you calibrate with any gas. Flush all ambient "air" out of the sensor's way with your backgas, calibrate it, wait for your tank gas to flush out of the sensor's way and start measuring ambient. Not nearly as easy as a lighter, but it'd certainly be a more accurate method.

You need to provide the same gas pressure you analyzed at to get an accurate sampling if I'm not mistaken.

[Aotus]

You need to provide the same gas pressure you analyzed at to get an accurate sampling if I'm not mistaken.

I expect the concerns raised about using an O2 analyzer are specific to those made for scuba applications. I'm not near a computer now, but expect it would be easy enough to find one for open-air use.

[Kirk]

When "dry" caving, I always keep a cigarette lighter in my pack. Not only does it help identify bad gas, but it also helps identify wind (a sure sign of going cave).

[victorzamora]

You need to provide the same gas pressure you analyzed at to get an accurate sampling if I'm not mistaken.

I haven't found that to be the case. I calibrate my analyzers on ambient air and analyze my tanks either with the airflow restrictor for LPI hoses or straight off the tank using the "ball" thing on the oxycheq analyzers. I always get good results that way. If I had a tank of air at the house, I'd try it to show you. Calibrate your analyzer on ambient air, then analyze your tank of air. Then calibrate it on the tank, and analyze ambient. If you're even mildly careful the readings should come out the same.....or close. It's certainly closer than "man, that flame is a smidge shorter than I remember it being."

[wingman]

I haven't found that to be the case. I calibrate my analyzers on ambient air and analyze my tanks either with the airflow restrictor for LPI hoses or straight off the tank using the "ball" thing on the oxycheq analyzers. I always get good results that way. If I had a tank of air at the house, I'd try it to show you. Calibrate your analyzer on ambient air, then analyze your tank of air. Then calibrate it on the tank, and analyze ambient. If you're even mildly careful the readings should come out the same.....or close. It's certainly closer than "man, that flame is a smidge shorter than I remember it being."

When I mentioned relative flame height I think a graduated scale is not the measure needed ...will the lighter even light or barely light is the issue. In the cave I was in the lighter barely lit and it was clear there was an O2 issue....not sure the scale on an analyzer will give any better info and as Jason mentioned the better deal is a co2 monitor. Bill

[victorzamora]

When I mentioned relative flame height I think a graduated scale is not the measure needed ...will the lighter even light or barely light is the issue. In the cave I was in the lighter barely lit and it was clear there was an O2 issue....not sure the scale on an analyzer will give any better info and as Jason mentioned the better deal is a co2 monitor. Bill

That's interesting. Thanks for clarifying!

[syntaxerrorsix]

I've got an Oxycheq analyzer and I can increase the O2 reading by increasing the pressure. I've not tried it with other analyzers.

[Nitrogenius]

You need to provide the same gas pressure you analyzed at to get an accurate sampling if I'm not mistaken.

I've got an Oxycheq analyzer and I can increase the O2 reading by increasing the pressure. I've not tried it with other analyzers.

Well you are right that an oxygen cell typically reads the partial pressure of oxygen rather than an oxygen fraction in an overall gas mix..
So there is a correlation to absolute pressure, but:


-From your diving computer/depth gauge you will know if a gas pocket/dry passage is at standard ambient pressure or compressed. If compressed you will get a higher reading than expected close to the surface and you coul even rougjly extrapolate the expected PO2 if the fraction was 21%


-it will still read PO2 and you body relys on PO2 in order to get enough oxygen. Hence even if it was a higher ambient pressure and a lower oxygen fraction as long as you get an PO2 reading above 0,16 bars you will not encounter an oxygen issue in the dry passage. Obvioulsy the issue of other toxic components in the gas remains..


Long story short the ambient pressure in regards to analyzing O2 with an analyser in a gas pocket/dry passage is a non-issue

[Skybluewater]

http://www.caveatlas.com/systems/sys...p?ID=287&co=US