The AirVisual Node/Pro uses a light scattering laser sensor for PM2.5 measurements.
How it works is that within the sensor's measuring 'chamber', a laser light beam is shone onto particles, and this light is
then irradiated in all directions from these particles
(scattering). A light detector (or 'photometer detector') then
measures all of this scattered light, and from this, the sensor can
calculate the concentration of particles within the chamber. In this way, the sensor is able to detect near microscopic particles ranging from 0.3μm to 2.5μm. The sensor in the AirVisual Node/Pro also has a small fan to ensure a constant flow of air
through the measuring chamber.
Each reading reported from the sensor is calibrated by a special algorithm which takes into account external temperature and humidity values.