Hi guys. Haz-Mat wonk checking in.
FWIW, the DOT regs only apply to the transportation of cylinders, the Compressed Gas Association (CGA) rules apply to consteruction, maintenance and storage.
See: www(dot)seco.noaa.gov/ENV/Factsheets/compressedGas.html
Doing a search for 1910.101 gets us this:
1910.101(a)
"Inspection of compressed gas cylinders." Each employer shall determine that compressed gas cylinders under his control are in a safe condition to the extent that this can be determined by visual inspection. Visual and other inspections shall be conducted as prescribed in the Hazardous Materials Regulations of the Department of Transportation (49 CFR parts 171-179 and 14 CFR part 103). Where those regulations are not applicable, visual and other inspections shall be conducted in accordance with Compressed Gas Association Pamphlets C-6-1968 and C-8-1962, which is incorporated by reference as specified in Sec. 1910.6.
A cool PDF from Sherwood here: www(dot)chemtech-usa.com/documentation/sherwood/TECHSPEC.pdf
IIRC the use of different threads is to prevent incompatible gases from being combined and creating a hazardous situation. I'm not sure if changing valves/threads is specifically
illegal per se... you might not be able to find a dive shop willing to refill a rethreaded SCBA cylinder*, but hey, were the fire service, right? We're the kings of adapt (pun intended) improvise and overcome. :support:
But as an employer, the FD might not want the liability of a "homebrewed" setup when there are commercially available setups for a reasonable expense.
FWIW I'd stick with actual made-for-diving tanks for breathing air, and simply use the existing airpack threads through adaptors as compressed air for lift bags or auxiliary use. After all, in this day of liability, if G-d forbid anything went wrong they'd be in search of who gave the :blessing:.
* A paramedic buddy (also a diver) from Madison WI tried to get some O2 cylinder refilled with medi grade gas at a welding shop. They had no problem filling the steel D's, but refused to fill the Al ones, claiming they "weren't standard cylinders"
Edit to remove URLs. Yar.