Taking common infrared gas detector as an example, explaining the principle of gas detector:

The Absorption spectrum can be measured to identify the types of the gas; the absorption intensity can be measured to identify the concentration of the gas. The infrared detector has wide range, not only can analyze the gas composition but also the solution composition. It has high sensitivity and quick reaction, and can be continuously indicated on line and consitituted a regulating system. The common infrared gas detector in industry is consist of two parallel optical systems with the same structure. One is the measurement room and one is the reference room. The two Chambers open and close the light path simultaneously or alternately with a certain period through the cutting plate. After the measured gas is introduced into the measurement room, The light that has been measured in the wavelength of the gas has been absorbed, so that the light flux in the infrared room is reduced through the light of the measuring room. The higher the concentration of the gas, the less the luminous flux into the infrared receiving chamber. The luminous flux through the reference chamber is certain, and the luminous flux into the infrared receiving chamber is also certain. Therefore, the higher the concentration of measured gas, the greater the difference in luminous flux through the measuring chamber and reference chamber.

We have a product using infrared gas filter technique:

Infrared CO2 gas detector is in compliance with the CO2 gas concentration detection, Adopting Infrared gas filter technique, the measurement can’t be interfered by other gas compositions.