A space heater is a device for heating an enclosed area. Space heating is generally employed to warm a small space, and is usually held in contrast with central heating, which warms many connected spaces at once. Permanently installed space heaters may use electricity or burn natural gas, propane, fuel oil or wood pellets. For portable use electric heaters are most appropriate, because gas heating can be very dangerous without a permanent flue.
Types of heaters
Space heaters can be divided into those that transfer their heat primarily by convection, or by radiation.
In convection heaters, heating elements either warm the air directly or heat oil or another filler, which in turn transfers heat to the air. The air then warms the objects and people in the space. Convective heaters are suitable for providing constant, diffuse heat in well-insulated rooms. Oil heaters warm up slowly but do not reach dangerous surface temperatures; wire-element heaters, which may be fan assisted, reach operating temperature much more quickly but may pose a fire hazard. One particular type of convective heater is the fan heater.
Halogen heaters usually comprise tungsten filaments in heat-resistant quartz envelopes, mounted in front of a metal reflector in a plastic case. They operate much like halogen light-bulbs, but radiate their energy primarily in the infrared spectrum. They convert up to 86% of their input power to radiant energy, losing the remainder to conductive and convective heat. The advantage of halogen heaters is that the radiation they produce is absorbed directly by clothing and skin, without first heating the air in the space. This makes them suitable for warming people in poorly-insulated rooms, or even outdoors.
Many of these space heaters, including those of oil-filled radiators and natural stone heaters, are plugged into an electric power source, most commonly a mains outlet. The power ratings of appliances are measured in kW, which allows an easy estimation of operation cost per hour, as energy is billed in kWh.
The two primary health risks from heaters are the risk of fire and the risk of carbon monoxide poisoning. The latter risk applies to gas and kerosene heaters but not electric heaters. The risk of fire from heaters may be mitigated by low surface temperatures (as found on oil-filled convective heaters), or by switches that cut power in the event of the device inadvertently being tipped over (often found in the bases of halogen heaters), or by thermal cut-out switches. Natural Stone Heaters do not pose a fire or carbon monoxide poisoning risk, and can be a safer alternative. However, the surface temperatures of the stone heaters can be considerable, though they may not cause an instant burn as the heat transfer is slow. For that reason they are usually mounted high on walls or ceilings, away from the reach of infants.
Within the United States, Underwriters Laboratories maintains standards UL 1278 for portable electric space heaters, and UL 1042 for portable and fixed baseboard electric heaters. The General Services Administration used to maintain Specification W-H-193 for electric space heaters, but this was cancelled in 1995 in favor of the UL standards. Additional information on portable heater safety may be found at the Department of Energy Energy Efficiency website. Also, the "EPA does not currently label space heaters as an ENERGY STAR qualified product...".
- "Space Heater Defined".
- 2008 ASHRAE Handbook - Heating, Ventilating, and Air-Conditioning Systems and Equipment (I-P Edition) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2008, Electronic ISBN 978-1-60119-795-5, table 2 page 15.3
- Underwriters Laboratories (2000-06-21). "UL 1278, Standard for Movable and Wall- or Ceiling-Hung Electric Room Heaters". Retrieved 2011-10-29.
- Underwriters Laboratories (2009-08-31). "UL 1042, Electric Baseboard Heating Equipment". Retrieved 2011-10-29.
- General Services Administration (1977-09-13). "W-H-193D, Heater, Space, Electric (Portable)". Retrieved 2011-10-29.
- Department of Energy (2011-02-09). "Portable Heaters". Retrieved 2011-10-29.
- Environmental Protection Agency. "Space Heaters". Retrieved 2011-10-29.
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