Talk to Chris Richardson of Deep6 about this. His regs, as the M1, were definitely developed with tech diving in mind. He also recommends max 80% O2 with his regs @ 3400 psi but 100% @ 2400 psi. It has to do with the specific partial pressure of O2 where things become unstable. AA just didn’t want to confuse people so they said 80% and left the relative pressure out of it. They’re in the extra cautious camp liability wise, but of course the M1 has been used with pure O2 since it came out and no issues have been reported. Regardless, Atomic seconds are a poor choice as a stage reg since they flood if you accidentally depressurize them during the dive.
Yes, people use M1s for tech diving. Including myself. But, I only have 2 of them and I use them for my backgas, not deco gas. I would have no problem using them for 100% O2 deco gas, if I had more of them, but I don't.
The issue of pressure merits noting that that only applies to the 1st stage. ScubaPro can make a piston 1st stage that is rated for 100% O2. I just don't see why Atomic can't/doesn't.
Your point about not using Atomic for stage/deco regs is a good one. And a reason why I have not really considered purchasing more M1s...
I guess if Atomic REALLY wanted the serious tech diver market (i.e. tech divers who use deco gases for accelerated deco, versus "less-serious" tech divers who only do deco on back gas) they would have to do a new 1st stage that they could/would rate for 100%, and also a new 2nd stage that did not have the Seat Saver feature.
Hey, watch it, I resemble
that remark.
I do not know where it comes from that regulators that we have to "suck" on or which are tuned stiff will conserve air or reduce consumption.
I think it came from a post upthread (don't remember who and too lazy to look it up). Somebody said that that's what they do/use.
Generally the greatest single contributor to the WOB in the loop
I'll stipulate to the accuracy of that, when WOB is measured on an ANSTI machine.
I am not at ALL convinced that it really matters a whole lot to us divers.
Example: The ScubaPro S620Ti came out shortly before I went through ScubaPro Reg Tech class. It was one of the regs we worked on. The SP rep was proud to point out that the S620Ti had the lowest WOB of any of their regs, and it was due to the improved exhaust design, as compared to their S600. They claimed a 30% improvement in WOB.
So, I bought 4 SP reg sets shortly after that class. 4 x Mk25 EVO, with 2 x G260 and 2 x S620Ti. I put them all together and did some dive testing using a G260 and a S620Ti on the same Mk25, with the same length hoses.
My experience was that I felt like the G260 breathed just a little nicer. It seemed like the inhale had just a tiny bit more "jamming air into your mouth" feeling than the S620Ti - or any of my other regs that I had at the time.
My gut feeling is that we humans are not so accustomed or adapted to really having to suck our air in. On the other hand, we do lots of things where we develop our ability to blow out against pressure. Inflating balloons, playing wind instruments, and many other examples come to mind.
So, my gut suggests to me that I am MUCH more sensitive (and averse) to things that make it harder to inhale, and I am fairly INsensitive to things that create some resistance to exhaling.
At least, that's my theory for why the S620Ti measures as having a lower WOB on a machine, but the G260 FELT better to breathe with at depth (my test went to around 90 feet, IIRC).