Gasoline heaters for cars never really took off because of potential hazards and safety but the practicality of them sound intriguing to me. Many people in the

Gasoline heaters for cars never really took off because of potential hazards and safety but the practicality of them sound intriguing to me. Many people in the midwest idle their cars till they are warm enough to be comfortable. I think this activity is now banned in some places. Besides gasoline heaters would it make sense for an entrepreneur to try to market an e85 heater (maybe less toxic than gas?) propane or diesel? Seems like such a thing could be popular with van campers or EV drivers if it could be made inherently safe.