What PurpleAir Sensors Measure
At this time, standard PurpleAir sensors measure particulate matter (0.3μg to 10μg), temperature, humidity, and pressure. However, we do have a limited number of Bosch BME680 sensors that also measure volatile organic compounds (VOC) emitted as gases. This sensor is in an experimental phase. Further details about the BME680 are available from the data sheet .
How We Measure Air Quality
PurpleAir sensors use PMS*003 series laser counters to measure particulate matter in real time (the asterisk ‘*’ represents a number determining the version of the laser counter). Each laser counter within a pair alternates five-second readings averaged over two minutes. Each laser counter uses a fan to draw a sample of air past a laser beam. The laser beam is reflected off any present particles onto a detection plate. The reflection is measured as a pulse by the detection plate. The length of this pulse determines the size of the particle. The number of pulses determines the particle count. These particle measurements are used to infer the mass concentrations of PM1.0, PM2.5, and PM10 for standard indoor and outdoor atmospheric particles. The product data manual from Plantower can provide more information.
PurpleAir sensors report real-time data that is updated every two minutes. Since air quality can fluctuate greatly throughout the day, the real-time PurpleAir AQI reading may appear “high” when compared to 12-hour averaged AQI data.