The real danger lies where you have fuel in liquid form on the ground or at the fuel neck where fuel vapors exit while the tank is being filled, neither of which are explosive. The most dangerous is an ignition at the fuel neck caused by a lit cigarette or static discharge. Filling up w/o the nozzle lock is safer and most self serve gas bars have removed these devices. If you calmly step back from a filler neck fire, it will usually go out or burn a bit like a candle until a fire extinguisher is used. Trouble escalates when someone, in a panic, removes the nozzle and proceeds to spread the fire all over