They don't inflate. The air valve that can be closed or opened is simply so that the vapor barrier that makes these boots a legend in cold weather does not burst when the airborne division jumps out of a plane, or when the non pressurized plane makes huge changes in altitude.
These boots were designed by the military for troops that were subjected to the very worst of weather conditions. I will wear nothing else but these babies when I'm in the places I inevitably end up working. My uncle and I fell through a creek on our snomobiles during a freak cold weather storm back home. We barely made it out with our lives. I was wearing my bunny boots, and he was wearing Sorrels. He didn't make it out of there with any of his 10 toes......
And he walks funny.