Ok. Pressurised containers are allowed on board.
I've done about a dozen trips, long and short haul with them ones at way higher pressures than co2. Every flight carries them, they're part of the on board equipment in many varieties from medical to the simple co2 capsules which inflate your life jackets under most people's seats when they pull that little string.
I'm sure RM ban them from flights. They're not banned from flights.
https://www.britishairways.com/en-gb...N_PHG_ALWAYSON
I suspect RM ban them like they ban everything else because they don't have the expertise to determine safety without inspection and jump for the lowest common denominator. Understandable but let's not say it's not possible because it is. All sorts of things can be flown, some need more paperwork, some don't.