Airlink is an air quality sensor from Davis Instruments that nicely integrates with your other Davis Instruments weather sensors. Vernier S&T sells it as order code DW-AIRLINK. Added:
The AirLink® Professional Air Quality Monitor can be used inside your home or outdoors. An AirLink Quality Monitor provides real-time Air Quality Index readings and sends them to your phone or computer. The air quality sensor measures particulates (PM) in the air by size: PM1, PM2.5, and PM10. The air quality meter gives you information both as data and as a color-coded graph that is easy to understand.