The Sensor Map shows health-based and instantaneous particle pollution for the Agency’s four-county region using EPA’s Air Quality Index colors. The map adjusts public, inexpensive air sensor data to the “gold-standard” Agency Monitoring Stations.  Air sensors can be a valuable addition to an air monitoring network, however care has to be taken to properly calibrate and check the quality of their data. Without calibration, the Purple Air sensors can read two times too high during an air pollution event like wildfire smoke! To calibrate the sensors, we use a calibration equation developed by EPA.   

Once the data are calibrated, they are put through a quality control (QC) process. This process removes data when the sensor is malfunctioning. Each Purple Air is also compared to all nearby sensors to see if it is reading within the range measured by the whole group. If a sensor is reading well, the sensor is assigned a high confidence value. This confidence value is in the popup that shows up after clicking on a Purple Air site. The higher the confidence, the higher quality the data are. Sensors with low confidence have circle markers that are more transparent. 

Purple Airs are just one of many types of air sensors. To learn more check out our sensor page.  

View the Air Quality Sensor Map.