Infrared flame detectors calibration and repair
Any object with a temperature greater than 0° Kelvin (-273° C emits IR radiation .The hotter the object, the greater the intensity of the IR emitted Normally,
Infra red detectors look for a flicker frequency within a nominal range that flames flicker at .IR detectors responds to infra-red radiation within a wave length of 4.2 to 4.7 microns, they have a longer vision range than UV detectors, especially with hydrocarbon fires. They are unsuitable for any fires where carbon is not present. Flares are susceptible to the shimmer effect of the sun reflecting on a flat sea and so should be located to look down on the area of protection avoiding the horizon as with UV detectors.
A common practice is to have two detectors looking at the same area but from different directions and a voting policy (ie. 2 out of 2) before alarm is generated in an attempt to prevent false alarm, as there are so many different sources of UV and IR radiation.
Dense fog, rain or ice can absorb IR radiation and reduce the sensitivity of the detector while it is less affected by the smoke than the UV detectors.