Infrared lamp

(electricity) An incandescent lamp which operates at reduced voltage with a filament temperature of 4000°F (2200°C) so that it radiates electromagnetic energy primarily in the infrared region.

A special type of incandescent lamp that is designed to produce energy in the infrared portion of the electromagnetic spectrum. The lamps produce radiant thermal energy which can be used to heat objects that intercept the radiation. An infrared lamp with a filament operating at 4000°F (2500 K) will release about 85% of its energy in the form of thermal radiant energy, about 15% as visible light, and a tiny fraction of a percent as ultraviolet energy. See also Heat radiation.

The lamps are supplied in two shapes. The most common shape, for general use, is the R lamp (illus. a), since the reflector unit is built in and the lamp needs only a suitable socket to form an infrared heating system. The other type of infrared lamp, the tubular quartz bulb lamp (illus. b), is used with a separate external reflector designed to distribute the heat as desired.

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Typical shapes of infrared lamps. (a) R lamp, with built-in reflector unit. (b) Tubular configuration with a quartz bulb.

The major advantage of infrared heating is that it is possible to heat a surface that intercepts the radiation without heating the air or other objects that surround the surface. Infrared lamps have many uses, including paint drying, evaporative drying, farm heating of animals, heating of food, control heating, and therapeutic heating of portions of the body to relieve muscle strains. See also Incandescent lamp; Infrared radiation.

An incandescent lamp having a higher percentage of the radiant power in the infrared region than a standard incandescent lamp; has longer average life owing to the lower filament temperature; may have a red glass bulb to reduce the radiated visible light.