This may be off topic but WHY would a space heater be used outdoors, let alone under a pair of fuel tanks??? My guess would be to try to keep them warm OR they wanted them to burn... "Pilotless electric ignition" comes to mind
Anyway that looks like quite the cooker, but at least it was outside when it self destructed!
That breaker, I have seen them at my old elementary school, they were those old "piggyback" style. They used them as switches---> in all the classrooms to protect AND control all the lights, outlets and fans.