Larry's post reminded me a TV program months ago showing a burning car. The driver got burned but ok. The cause was a leaking gas cylinder (possibly the type used for BBQ party) stored in the car. When the driver turned the ignition key, the spark started the explosion.
If you charge the a/c with hydrocarbon type refrigerants (flammable, ban in some States), and the A/C coil leaks inside your car. You have a live bomb waiting to explode.