There was mention of CO2 being added to food
containers, to ensure killing critters that might want to breathe air in them. That's how CO2 got involved. You mentioned a reluctance to carry 10 or 20# bottles of it, which are essentially the same as extinguishers, which is why I mentioned extinguishers.
Securing a CO2 bottle is no big deal, if you can secure a battery
, you've already got the skills for it. And if it is an extinguisher, hopefully there's a secure mount for it. Personally, I like the "no clean up" aspect of CO2 extinguishers. And it would take a truly gross leak to cause a problem from a CO2 bottle of any kind in the room (cabin) assuming you've got normal ventilation. CO2 poisoning isn't like C) poisoning, you'll be tipped off that you need to go on deck
for air long before it endangers you.