Getting the most out of your O2 tank

OceanOpportunity

as more a matter of poor-form than anything, from time to time, I use (not consume necessarily) more O2 in the shallows...probably some subconcious over-confidence that leads me to scurry around and do more of a saw-toothe than as if I were on a deep, mission specific dive.

my O2 metabolism is very low.. 0.5 lpm-ish. But when I account for what I 'waste' calibrating cells, flushing the loop to pure O2 at my last stop, etc etc...it ends up just over 1 lpm... there are lots of ways to waste gas, especially when you are carrying to little of it to begin with!

you can always carry some offboard O2 to plug in to

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Nick uk.

Their is a very good reason for doing these things and therefore i wouldn't call it 'WASTING O2'...................

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bgpartri

My O2 consumption varies depending on needs. In local diving I just don't even think about it. I let the solenoid control the injections and will leave it on high setpoint up to the 20ft/3m stop. At 20 feet, I switch to low setpoint, flush with O2 and just use it as an oxygen rebreather for the rest of the dive.

O2 is cheap and easy to get here. I have all the whips and stuff, but I stopped filling myself. The LDS has O2 and a booster for $0.35/cu/ft and compared to the cost of the hotel, ferry, sorb, and dive boat, it just isn't worth worrying about. Of course it helps that the dive boat doesn't charge for O2 fills for rebreathers. He says it costs him less than the air fills for the OC divers.

If I'm someplace where O2 consumption is critical, I will switch to low setpoint for the ascent. For ascent to the first stop, I will just let the ppo2 drop, and only inject if it's a long ascent. Of course the key skill here is exhale first, then inject. (Yes, I know - MOD 1) When I move to the next stop, I exhale some gas, then go up, and top up the o2 at the stop. (after exhaling first) Again, switch to oxygen rebreather for 20ft and up.

It's pretty easy to halve your consumption.

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Abbo

Thanks. In my struggle to be brief I became obscure. What interests me most is reducing waste - less for logistical reasons and more for the discipline of honing the skills. If you're correct that a diver actually metabolizes 0.7 to 1.1 litres of oxygen a minute on a regular dive, and yet divers find they use an average of 1 to 2 litres, then the range of waste is 0.3 to 0.9 litres. The difference is a factor of 3. I assumed that everyone is implementing what is taught in every Mod 1 to a greater or lesser extent: what I was interested in is whether there are any additional tricks that get people to the 0.3 end of the spectrum?

Gill Envy

I don't do square profilles so to some extent it's a loosing battle to conserve oxygen and i'm doing mostly 40 m dives so it's not a big deal. I dive very similarly to how I used to dive OC just spend more time at it. I buy 02 in bulk, trans fill and don't worry about it. o2 is cheap, like really cheap around here...the fill cost is almost the same weather buying a 13 cf, 80 cf or filling a big welding bottle. You pay more for the hazards and inconvenience of filling than for the volume it seems.

If you are doing deep square profilles where conservation is more of a concern, i'm not the one to comment.

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Abbo

I find I nudge the ADV by mistake quite a lot, so I've taken to having it switched off most of the time. That helps me to think more about minimum loop volume, squirting in a little O2 when the volume gets a little tight. Yes, obviously dropping the set point on ascent to avoid the controller chasing the set point: I was switching to 0.4 at 10m to give a margin for error for hypoxia. At 95kg, I am likely to metabolize O2 quite fast, but I can't help think that there is more I can do to husband the gas better, which will be more of an issue when I get back to diving mix.

decoweenie

I spoke to someone yesterday who dives a Boris, and unless I misunderstood, the Boris has 2 different O2 injection algorithms specifically tailored for the descend and ascend portions.

Could someone explain how they work ? Thanks...

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SteveL

I belive this is very wrong (and dangerous) and I hope you dont get dave sutton started - as he also has a strong view to the contary.

Steve

Hanssing

Well I wrote I would shut up now.....
SO I'm now wispering with my hand over my mouth

The amout of "wasted" O2 released to the water is proportional to TOTAL Loop volume (and not CL-volume as I wrote) wich is perhaps more like 10 l.
So amount of gas wasted is more like 11l pure O2, from 40m ot 3m.

I know Dave feels strongly about hypoix Dil (and I agree), so one should not run the ppo as low as the loop contents becomes hypoxic at surface, but I also wrote that, though a bit further down.

Anyway I (will) pay 0.01$ pr. litre O2 and I personally wont bother, but will keep my own rEvodream Green and happy. But the issue raised is not economics, but how one can save O2 through technique - and this is one way. If done to extremes it becomes dangerous, if done wiht moderation it does not. But it will save a little O2, unless you hang for 10 more minuttes.

Yup, I didn't write a word

Nicolai

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Abbo

Would you care to elaborate? Presumably you are saying be really careful not to let the decrease in pressure take the loop hypoxic? But I also don't want the solenoid firing away wastefully trying to chase a high setpoint. Since I took Mod1 on an mCCR before the Meg Mod1 I believe I am quite careful at watching the handsets, and am happy to manually inject when I think I can metabolise it, rather than let the program merrily fire my O2 off into the atmosphere.