i was thinking heating with miners is not healthy, as the electronics are releasing toxic materials into the air.
As long as the temperature of the PCB is less than 300 degree, there is no problem about toxic materials.
Actually it's how much time you spend in the room with the miners what's matters. Toxic materials go into the air always when heat is applied but not as much as to poison you right away. Don't spend a lot of time where the miners operate and you shouldn't sleep there that's for sure.