A kerosene heater, also known as a paraffin heater, is a portable, unvente, kerosene-fueled, space-heating device. In the United States they are used mainly for supplemental heat or as a source of emergency heat during a power outage. In some countries, particularly in Japan, they are used as the primary source of home heat. Most kerosene heaters produce between 3.3 and 6.8 kW (11000 to 23000 BTU per hour).