QuoVadis
Contributor
Two divers, one on Nitrox the other on regular air........If a problem arises and one or the other has to share air, are there any problems breathing Nitrox (or vice-versa) after breathing regular air for 40 minutes????
Riddle me this............
- Thread starter QuoVadis
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Wijbrandus
Contributor
I would say that depends on the depth and time down there.
Since you will be surfacing immediately anyway, and are above the MOD for the nitrox mix, I can't see much impact on either of you. That's just by looking at the two sets of tables though. I'm no mixed gas expert.
Since you will be surfacing immediately anyway, and are above the MOD for the nitrox mix, I can't see much impact on either of you. That's just by looking at the two sets of tables though. I'm no mixed gas expert.
Pretty much if you are in rec limits and PPO2 MOD limits it wouldnt matter - due to the low risk involved (the donor is also breathing nitrox at that depth), also sharing air is typically a temporary thing (ie up to surface) and just that short time wouldnt cause any troubles - firstly due to the fact there is no hard line (its more a time period at higher PPO2 than exactly x mins - kind of like NDL limits) to cross and again i refer back to the donor using it.
No if a diver doesnt have training and goes ahead and uses nitrox for a whole dive not knowing their FO2 and MOD, NDL and a whole bunch of other stuff, then trouble can start - but that wasnt your question.
Also from what i gather, tech divers often switch from low FO2 gases up to higher FO2 gases at shallower depths for deco or travel gas etc - hence increasing your fraction of O2 will not do anything to you assuming you are within the limits of that mix and your O2 per day limit (OTU) - which would be hard to push if you were on air prior to the switch of gas to a higher FO2 mix.
No if a diver doesnt have training and goes ahead and uses nitrox for a whole dive not knowing their FO2 and MOD, NDL and a whole bunch of other stuff, then trouble can start - but that wasnt your question.
Also from what i gather, tech divers often switch from low FO2 gases up to higher FO2 gases at shallower depths for deco or travel gas etc - hence increasing your fraction of O2 will not do anything to you assuming you are within the limits of that mix and your O2 per day limit (OTU) - which would be hard to push if you were on air prior to the switch of gas to a higher FO2 mix.
Even if it was a bad thing, which it isnt, its better than the alternative.
Besides, when things go to crap on the bottom you just won't give a darn what your breathing as long as it's something.
Gary D.
Besides, when things go to crap on the bottom you just won't give a darn what your breathing as long as it's something.
Gary D.
But you may have to account for your O2 clock if you subsequently dive enriched air later on.
NOVIZWHIZ
Contributor
Yeah really - something other than water........Gary D.:
no problem what so ever. It should only be for a minute or so while they surface, so even the effects on the subsequent dives would be almost too small to calculate.
Yep...beats suckin water.
Windwalker
Contributor
If the Nitrox diver is below his MOD then there is another problem to consider, I dive Nitrox and my buddies dive Air. Every once in a while when we surface, if one of my buds has a headache, I will let him suck off my Nitrox for a bit. If we were at depth and he had to breath of my Nitrox, it would be arguably safer for him to breath off my nitrox because of the change of PP of Nitrogen, so he would start the Nitrogen offgas sooner. Asuming I did have to share air with a buddy and we did surface, I would take a longer then usual surface interval anyways just to let the stress reduce itself. I might also call a cessation to any further diving for the day. Once an OOA emergency happens that is one major stressor that can affect the rest of the diving for the day. There would be no problem breathing off air if I ran out of nitrox either. its just for a short time while we surface together. Now the one problem that I have been wondering about is Rebreather diving with someone who is OC. But that is a question for another time.
H2Andy
Contributor
this is what i would do:
if you switch from nitrox to air, you might just have gone over your NDL. i would terminate the dive and ascend immediately (but safely). track your O2 clock as though the entire dive was done on Nitrox and you'll be on the safe side.
if you switch from air to nitrox, also ascend immediately. take a minimum one hour surface interval; add up your O2 clock time; triple-check that you weren't exposed to over 1.6 ata. treat the entire dive as an air dive for NDL purposes and as nitrox dive (for whatever mix) for O2 clock purposes.
the only immediate danger is that you will switch to a Nitrox mix that is not suitable for whatever depth you are at. if you absolutely have to breathe (and you do), just ascend as quickly (and as safely) as possible to the surface.
these are "safe as safe can be" solutions. once you check
your exposures and so on, it will turn out that you don't have anything to worry about 99% of the time.
if you switch from nitrox to air, you might just have gone over your NDL. i would terminate the dive and ascend immediately (but safely). track your O2 clock as though the entire dive was done on Nitrox and you'll be on the safe side.
if you switch from air to nitrox, also ascend immediately. take a minimum one hour surface interval; add up your O2 clock time; triple-check that you weren't exposed to over 1.6 ata. treat the entire dive as an air dive for NDL purposes and as nitrox dive (for whatever mix) for O2 clock purposes.
the only immediate danger is that you will switch to a Nitrox mix that is not suitable for whatever depth you are at. if you absolutely have to breathe (and you do), just ascend as quickly (and as safely) as possible to the surface.
these are "safe as safe can be" solutions. once you check
your exposures and so on, it will turn out that you don't have anything to worry about 99% of the time.
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