It would be nice to have something inside your inventory to equip. Even if it only filled the tank half way, would still help if you run out of oxygen. I did have an idea of placing a "refill" station near Red Harbor, some sort of tank that supplies air for the same price as the NPC. Not impossible, just needs to be thought about a bit more. Thanks for posting!
Billy
This is very easy to do. Just need to know how you want it done.