I thought of that and the terminals are covered and the fuel is vented external to the case. Being a chemist, I looked at the setup pretty carefully - don't need to blow myself up at home! There isn't enought voltage in the battery to arc accross the teminals even if there is fuel vapor in the case. The vapor pressure of the fuel is fairly low and the flash point fairly high (considering many other fuels). I used to use ethanol and an open spark source quite a bit in the same closed space (ethanol has a much higher vapor pressure and a significantly lower flashpoint. Never really had a problem. The ethanol flame is near invisible as well and not all that hot (relativly).