[Doxin]

A nozzle clog won't set a 3d printer on fire either. It'll make a good mess of the hot-end. There'll be a bunch of charred filament, and heat creep will clog the nozzle nicely. It won't however magically get any hotter than it does while printing with an unclogged nozzle.

What does cause fires is failed thermistors. These days most firmware will detect unreasonably high or unreasonably low temperature readings and turn off the heaters. You thermistor can still however fail with a reasonable reading if you're very unlucky.

Another factor is MOSFET failure. MOSFETs have a failure mode where they can fail closed. This can turn a heater on permanently. Modern firmwares will detect the temperature going unreasonably high, but most hardware is not set up such that the firmware can do much about it.