Formaldehyde sensors, a subdivision of gas sensors, are specially used for detecting formaldehyde content in the air. Formaldehyde is a colorless irritant gas. Usually, in the process of decoration, there will be a large amount of formaldehyde, doing harm to people's health. Therefore, in order to monitor indoor formaldehyde, it is necessary to apply the equipment containing formaldehyde sensors for detection. This type of sensor has accurate formaldehyde sensing performance, and its cross-sensitivity to other volatile organic compounds is very low.

Formaldehyde sensors on the market are mainly electrochemical and semiconductor gas sensors. The working principle of the electrochemical formaldehyde sensor is based on chemical electrode reactions. And it mainly contains a working electrode and an active auxiliary electrode. The signals from the auxiliary electrode and the working electrode can be used for temperature compensation to enhance the selectivity of the whole sensor. The formaldehyde and oxygen undergo corresponding redox reactions on the working and counter electrode, and the charge is released to form a current. Hence, the concentration of formaldehyde can be determined by the current, and quantitative detection can be achieved.

And the principle of the semiconductor formaldehyde sensor is that under certain temperature conditions, when the gas to be measured reaches the surface of the semiconductor sensitive material, it will chemically react with the oxygen absorbed on the surface, leading to the change of the resistance of the semiconductor material. The gas concentration can be monitored by measuring this change. The semiconductor formaldehyde sensor can realize limited gas identification and qualitative detection in a known environment through methods of selective catalysis and physics.