mech once bubbled...
As much as I like my Atomic I'm thinking that the next regulator I buy for me or the family will be Apecs (sp?) because titanium and oxygen over 30% (I believe) is not a good mix.
I believe than regular nitrox is not an issue but more than that is not a good thing.There are also other issues like cleaning and prep w/viton.
First of all, it's Apeks.
Atomic states that all their regulators are good for use up to 40% Nitrox, out of the box. For recreational diving, 40% is the highest you'll ever be using, so this is quite enough. Even the fully titanium T1.
If, on the other hand, you will be doing technical diving with high O2 deco gasses, then you will need to use >40% mixes. In this case, Atomic wants you to use the M1, which they say is good for 80% O2, out of the box. This is the company line.
Now, as for the materials, the T1, is fully titanium, except for the stainless steel spring and piston in the first stage. All the metal components in the second stage are also titanium. The B1, has the same second stage, but the first stage is all brass, except for the stainless steel spring (same as T1) and the stainless steel piston. The Z1, has the same materials as in the B1 in the first stage, but just replaces the Titanium body of the second stage with zirconium/palladium plated brass. The M1, has exactly the same first stage as the B1, but has a piston that is made of monel instead of stainless steel. The second stage of the M1 is the same as the Z1, but has a stainless steel orifice instead of the titanium orifice. AFAIK, all soft parts(o-rings, etc.) are identical, O2 compatible, and only O2 compatible lube is used.
For all, the second stage spring and spring lever are made of titanium. But those are all in ambient pressure.
In the B1, the titanium second stage barrel and orifice contact the LP side. In the Z1, the titanium orifice contacts the LP side. I don't think this is a problem, as someone else also said, but don't take my word for it.
I suspect that the reason Atomic changed the piston to monel on the M1 is that stainless steel generates sparks relatively easily, and also can burn in 1500psi O2 if heat is applied (I heard it from someone on Scubaboard). Although Atomic says only 80% for the M1, I have a feeling it's for liability reasons, and it should be safer on 100% than most O2 compatible regs out there, as it is the only regulator using monel(highly O2 resistant) for that part.
I am currently looking into whether I can get a monel piston retrofit to a B1 or Z1 first stage. If so, I think it should be good for 100% once cleaned, as it will be identical to the M1 first stage.
As for the second stage, switching the Ti orifice of a Z1 to the SS one used in the M1 will make it identical to the M1. (Although I'm inclined to believe it's probably not a problem, even with a fully Ti second stage like the B1.)