The other temptation with space heaters is to close off the door to heat up the room. "A space heater or a wood stove is probably going to heat one room really well," says Rochman. "But there's a tradeoff between wanting to be safe and energy-efficient. It's good to have ventilation because heat dries things out." Still, she adds, "people have been using alternative heating sources forever and they can be used safely if you follow the instructions."