Its because, more than likely, they can inadvertantly inflate. So if you were to dishcarge them, empty the bottle then they can be sent. I have to send a Life Raft back to Eastern Areo Marine in Miami (for service) next week and I have to disconect and empty the CO2 bottle before shipping it with FEDEX.
I believe they can send it back afterservicing but it must be disconnected and properly classified with appropriate HAZMAT or DG paperwork.
Sheep