The PurpleAir PA-II uses a laser particle counter (PMS5003, PMS1003) to provide real-time measurements of PM1.0, PM2.5 and PM10. The PA-II is located 2 m from the west side of the building about 1 m above ground. The sensors count suspended particles in sizes of 0.3, 0.5, 1.0, 2.5, 5.0, and 10 µm and then use an algorithm to estimate the PM concentrations in µg/m3. The PurpleAir web site contains more detailed technical information about the sampler as well as links to map showing nearby locations deploying PurpleAir sensors. The measurements are averaged and saved every two minutes. Uploads to the web server occur at less frequent intervals. The long-term air quality data archive can be accessed by the end time of each six hour segment starting 4 May 2020.