When measuring the gas concentration of Carbon dioxide CO2 and Methane CH4, use the Infrared sensor, here mainly about the working principle of the Infrared gas detector.

From this absorption spectra could be judged the gas type ; measuring the absorption can intensity the gas concentration . Infrared gas detector with a wide range, not only can analyze the gas composition also be suitable for solution components,  high sensitivity, rapid response, continuously online instructions , also could be composed conditioning systems.  For the industrial infrared gas detector, usually consist of two indentical system.

One is a measuring chamber, the other is a reference room. Two chambers by cutting the light panels in a predetermined cycle simultaneously or alternately opening and closing the optical path. After the measurement gas introduced into the test chamber, the test gas having a specific wavelength is absorbed, so that the optical path through the measuring chamber into the receiving chamber of the infrared luminous flux reduction. The higher the gas concentration, the less infrared receiver into the chamber flux; and through the reference room of the flux is constant, also the flux into the infrared receiver chamber is certain.

Therefore, the higher the concentration of the test gas through the measuring chamber and the reference chamber, the greater the difference between the flux. This flux is a certain difference between the amplitude of the vibration period is projected onto the infrared receiver chamber. Receiving chamber with a few microns thick metal thin film divided into two halves, the interior seal has a greater concentration of the gas component measured in the absorption wavelength range can absorb all incident infrared rays, so that the light flux pulsation becomes temperature cycle, and then can make changes according to temperature gas equation is converted to pressure changes, and then use capacitive sensors to detect, after the enlargement process indicates the measured gas concentration. Except capacitive sensors, it can also be used directly to detect an infrared quantum type infrared sensors, and infrared wavelength selection and interference filters with tunable lasers as the light source, the formation of a new all-solid-type infrared gas detector. This detector with only one light source, a measuring chamber, an infrared sensor will be able to complete the measurement of gas concentration. In addition, the use of a filter with a plurality of different wavelengths of the optical disc, then simultaneously are multicomponent gas concentration in the measurement of various gases.