PurpleAir sensors are low-cost, community-owned devices that measure airborne particulate matter (PM) in real time. They contribute to a global network displaying hyper-local air quality data, accessible to everyone via the PurpleAir map.
Here’s a summary of key aspects:
- Measurement Capabilities:
- PurpleAir sensors primarily measure particulate matter (PM), including PM1.0, PM2.5, and PM10. They use two internal lasers to count particles by size (0.3, 0.5, 1, 2.5, 5, and 10 μm) and then calculate mass concentrations.
- Some PurpleAir sensors also measure volatile organic compounds (VOCs), temperature, pressure, and relative humidity. Note that temperature and humidity readings reflect the sensor’s internal environment and may require correction to accurately represent ambient conditions.
- How They Work:
- Each sensor uploads data to the PurpleAir map in real time, typically every two minutes.
- The sensors use Plantower laser counters to measure particulate matter. A fan draws air past a laser beam, and the reflected light pulses from particles are measured to determine particle size and count.
- Data Accuracy and Use:
- PurpleAir sensors have been found to be highly precise for PM2.5 and PM1 estimates. However, they may underestimate PM10 pollution levels and can have biases, especially at extreme concentrations of smoke or dust.
- The U.S. EPA has developed correction equations for PurpleAir data, and corrected data is integrated into platforms like the AirNow website, improving the spatial coverage of PM2.5 information.
- The data from PurpleAir sensors is valuable for understanding localized air quality, particularly during events like wildfires, and for filling gaps in traditional regulatory monitoring networks. It’s also used in various research projects globally.
- Air Quality Index (AQI):
- The PurpleAir map displays air quality data compared to the Air Quality Index (AQI), a guide from the EPA that quantifies air quality thresholds and their health impacts. The AQI uses colors to indicate different levels of concern, from “Good” (Green, 0-50 AQI) to “Hazardous” (Maroon, 301+ AQI).
- Accessibility and Community Involvement:
- The PurpleAir map is a web application that allows users to view data from sensors worldwide.
- Various projects and initiatives loan or provide PurpleAir sensors to residents, empowering communities to monitor air pollution in their neighborhoods and contribute to environmental understanding and improvements.
For more detailed information, you can explore the following resources:
- Purple Air Brochure
- What Do PurpleAir Sensors Measure and How Do They Work?
- Real-time Air Quality Monitoring by PurpleAir
- Correction and Accuracy of PurpleAir PM2.5 Measurements for Extreme Wildfire Smoke
- An evaluation of the U.S. EPA’s correction equation for PurpleAir sensor data in smoke, dust, and wintertime urban pollution events – AMT
- PurpleAir Sensor Project | doee
