The core component of infrared heaters is a light bulb that produces infrared light. In some units, this light is directed toward objects; in other units, this light shines on metal within the unit to create warm air that is blown through the room.
All light creates heat when it strikes objects. While visible light typically produces little heating, infrared light, which has wavelengths too short for people to see, is more efficient at heating objects. This makes infrared light an efficient and safe option for heating objects.
Many infrared heaters are directed toward objects, which then heat up. Since the air is only heated when the heat from warmed objects radiates away, these types of infrared heaters are inefficient at heating rooms. In small spaces, however, they can create a relatively warm area, and they can warm people directly, which leads to high efficiency.
Other infrared heaters shine the infrared light directly onto an object capable of absorbing infrared heat well, and a fan then blows air over the hot metal, creating warm air. These units vary in efficiency considerably, but some compare reasonably well with other types of space heaters. Compared to central heating systems and wall furnaces, however, infrared heaters are generally expensive to run. Portable units are often used for camping or use outdoors.