Luminous radiant gas heaters – also known as infrared heaters – emit thermal radiation in the wavelength spectrum visible to the human eye – hence the name. Conventional gas-fired radiant heaters use a gaseous fuel that is pre-mixed with the required amount of air in a special injector, known as a premix system. The homogenised gas/air mixture passes through a perforated ceramic plate where the combustion process takes place. At operating temperatures of 850 to 950°C, the ceramic combustion surface begins to glow and becomes the radiating surface. The ceramic radiating surface is partially surrounded by elaborate reflectors that collect and direct the infrared radiation to the space to be heated.

Modern luminous radiant gas heater designs, known as combi radiators, use the reflector surface heated by the exhaust gases as an additional radiating surface. Luminous radiant gas heaters are installed under the ceiling or upper walls. As with tube gas heaters, minimum installation heights of 3.5 to 9 m must be observed to avoid areas of high radiation intensity.
The heat-up time is very short. Full output is achieved within 5 minutes of switching on. In medium and large halls, several individual heaters must be installed to provide even coverage to meet the heat demand.

With surface tempertures of 850 to 950 °C combustion takes place directly on the ceramic plaque where a large amount of the generated heat is converted into infrared heat radiation. The forming of NOX is suppressed.