How does self inflatables work?

Answer 1

If your question is about self-inflating tires the best answer you can find is in the link below.
http://auto.howstuffworks.com/self-inflating-tire.htm/printable

Answer 2

Self inflating life jackets have a gas cylinder whose valve is kept closed by a water disolvable string. If you fall into the water, the string disolves, the valve opens, and the life jacket inflates. When you get done with it, you can get it recharged and reset for about $45.