Space heating

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 burn natural gas, propane, fuel oil, or wood pellets; use electricity for resistance heating; or use a heat pump that can also provide air conditioning. For portable use, electric heaters are most appropriate because gas heating can be very dangerous without a permanent flue.

Space heaters can be divided into those that transfer their heat to the required space 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, produce warm air more quickly but may pose a fire hazard. One particular type of convective heater is the fan heater.

The main advantage of radiative heaters is that the infrared 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. It also allows for greater distance between the people and heater.

Some of the earliest electric heaters were radiative, consisting of Nichrome heating wires held by ceramic or mica insulation at the focal point of a (usually) polished metal reflector. The cost was very low since nothing else, not even a switch, was needed. Later models included a wire guard preventing accidental contact with the heating wires or the hot ceramic.

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