You should check with the airline. You might also check with any local org. that governs airports/air space. American Airlines recently allowed a group of us to carry 2 cartridges per person, max 16 g. each, as carry-on (apparently same or less pressure as in inflatable life vests). The flight connected in London (en route to Frankfurt) and British Airways (partner on 2nd leg of flight) also said nothing about the 2 cartridges on our persons when going through security at Heathrow.

Returning from Frankfurt was another story. German airport officials escorted us to British Airways counter with cartridges--the BA employee confiscated the cartridges saying it was not BA's policy to disallow carrying CO2, but the policy of German airport authority (who I'm guessing set local policy for all air carriers that pre-empt an airline's policy).

Go figure.

I wasn't allowed to bring my 16 gram cartridges on Jet Blue to Wash. State. I agree, call the airline in advance and be upfront.