The following organizations have conducted evaluations of the PA-II sensor: South Coast Air Quality Management District’s Air Quality Sensor Performance Evaluation Center (AQ-SPEC), EPA, San Joaquin Valley Air Pollution Control District, and Atmospheric Environment. South Coast Air Quality Management District has also evaluated the PA-I-Indoor sensor.
PurpleAir sensors, when subjected to studies such as one from the South Coast Air Quality Management District, have performed very well against regulatory sensors. There are two major differences between PurpleAir sensors and regulatory particulate matter sensors: the methods used to measure particulate matter, and the averaging time of the data collected.
Regulatory sensors typically measure the mass concentration of particulate matter (PM) using methods that account for variation in particle density. This method is cost-prohibitive and requires extensive field infrastructure support, and reporting occurs on an hourly basis at best. Because of this, many cities have a limited number of these sensors, if any at all. This isn’t feasible for the average citizen to own one.