The Laser Dust Sensor is used to measure the concentration of suspended particles in the air with different sizes (including PM2 5). It uses a laser diode as the light source to illuminate the sampling air boosted by the blower. When the small particles in the air enter the illuminated area, the laser beam is scattered. The scattered light is received by a photodetector and converted into current signal which is amplified and processed then to indicate the concentration of particles. A built-in microprocessor converts it into mass concentration (μg m3) and outputs the signal via universal digital interface.