Here's whats happening. You know that Aerosol cans are explosive in nature.And when the man sprays the liquid fire on the rim of the tire, and INSIDE the tire, it rebounds off the rim and goes in. And when he lights the spray and lights the gases inside the tires, all of the "liquid fire" ignits and expands with heat. Thus increasing the pressure inside the tire. And that makes the tire inflate extremely fast.
http://madzindia.blogspot.co.il/2010/12/instant-tire-inflate-with-with-liquid.html