For a PM2.5 detector, the sensor is the foundation. The quality of the sensor determines the working quality and performance of the finished detector. As the "eyes" of the detector, the sensor can quickly probe and reflect air quality conditions and provide timely feedback to users.

Currently, the common PM2.5 sensors on the market are mainly divided into infrared probes and laser probes. The principle of infrared dust sensors is to use visible infrared light to analyze and identify particulate matter with a diameter of 0.5 micrometers or more, calculating the particulate matter concentration through light scattering algorithms. One difference between infrared dust sensors and laser dust sensors is that infrared dust sensors do not have an internal fan; the airflow is passive, relying on resistor heating to promote airflow, resulting in smaller airflow and data volume. Laser dust sensors have a built-in fan that can actively inhale airflow, providing stable airflow and obtaining more data.

Laser particulate matter sensors can obtain the accurate concentration of particulate matter with diameters of 0.1-2.5 micrometers in a unit volume of air. Typically, the wavelength of common red-light laser is 630-650 micrometers, with half-wave diffraction at 630-650 nanometers; particulate matter above 300 nanometers (i.e., 0.3 micrometers) can be accurately detected.