Geo7
Contributor
Probably not vastly superior. I think an unbalanced piston like the Mk2 is best. The way I understand it, Monel does not decrease the probability of a fire. After all the Scubapro Mk25 is available for 100% O2, as are various diaphragm regs. They all seem to pass the ASTM G175 - 13 oxygen ignition sensitivity test, where a burning pill is released inside the reg filled with O2. The reg passes the test if the damage is within certain limits. More details of this test procuedure can be found linked above. The Monel is less likely to catch fire, if something else (e.g. contamination) burns inside the reg. So Atomic uses it in specific locations.There have been entire rebreathers that went up in flames, so knowing the reg will likely stop small sparks should be a good thing. The reasoning of Atomic is that you can use the m1 as a non-dedicated reg up to 50% O2 with little risk (where air purity is uncertain).
The reason I made the comment about having more confidence in the M1 is that ironically, even though the M1 is better engineered for O2 than other regs that enjoy a 100% rating, it only gets an 80% rating. My guess is that is has to do with insurance. Or perhaps otherwise very high standards. As you know most other regs are succesfully used for all this, so you could say we are splitting hairs here and I won't object.
Monel also conducts heat better than a steel piston, and Atomic claim better performance in cold water. Similar for the steel orifice in the second stage as compared to titanium. The Monel piston in the T2X performed so well with regards to corrosion, that they gave the T3 a 3-year service interval, but in the M1 you'd still want to clean the brass body after a while. It is a great reg, but yeah, huge tech dives are being done with much cheaper regs.
PS: Steel corrodes quickly when in contact with Monel, so a Monel piston in an ST1 1st stage may be a problem.
