Space heater

Space heater
     A space heater is a self-contained device for heating an enclosed area.[1] 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. Space heaters are usually portable or wall-mounted, and may use natural gas or propane, but are most commonly electric

Types of heating
     Space heaters can be divided into those that transfer their heat primarily by convection, or by radiation.
Convective heaters
     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.
Radiative heaters
     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.

Power Sources
Electric heaters
An electric fan heater.
     Modern electric space heaters may have ceramic or nichrome heating elements, and may be fan-forced with a blower or a squirrel-cage fan to improve heat transfer. Window or wall-mounted units, often seen in hotel rooms, are permanent space heaters. These often employ efficient heat pumps, which use reverse-cycle air conditioning to transfer heat to the inside from the outside.
Gas heaters
     Gas heaters use propane, butane, or liquefied petroleum gas. They may be convective or radiative, in the latter case by heating a matrix which then emits infra-red radiation. Gas heaters burn their fuel in air and produce carbon dioxide. In well-insulated rooms the oxygen concentration may drop and carbon monoxide may accumulate to toxic levels due to incomplete combustion. For this reason gas heaters should be used only in rooms with adequate ventilation. When used outdoors, for example as patio heaters, they present the dual advantage of portability and higher output (due to not being constrained by the current-carrying capacity of electrical wiring).
Kerosene heaters
     A Japanese space heater that burns kerosene for fuel. It contains an electric fan and computer controls.
Kerosene heaters were once common, and are still widely used in some regions. Paraffin is used to heat many informal dwellings in South Africa, where it poses a risk of fire and carbon monoxide poisoning.
Safety issues
     The two primary health risks from heaters are the risk of fire, and the risk of carbon monoxide poisoning. The latter risk accompanies gas and kerosene heaters but not electric ones. The risk of fire from electric 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 being knocked over (often found in the bases of halogen heaters), or by thermal cut-out switches. The EPA does not consider space heaters as an Energy Star-qualified product.