I need to make the design of car floatation devices. In my case, the airbag/raft is for floating the car in case of floods. I am considering to use Sodium Azide, just like in car airbags, but it inflates very fast and shrinks in a short time. Is there any other chemical reaction that can produce a large quantity of gas (1000L+) in a relatively quick time? Or is there a way for me to slow down the sodium azide decomposition so it doesn't get too hot and shrink after?