After being housebound for 2 weeks by the September 2020 west coast wildfires, I decided that I wanted a way to measure conditions outside of my house and record them over time. I built the ESParticle to measure particle count in the air, as well as temperature and pressure. It's loosely based on the Sensorbot.
The hardware consists of ESP32 with a BMP280 Temp/Altitude/Pressure sensor and a PMS5003 particle sensor. The ESP sends periodic data to a Thingsboard server on a Raspberry Pi, which, and hosts a website on the local network with plots of the logged data.
Install the software using PlatformIO. I've provided a sample "example-secrets.h" file that should be copied to "secrets.h" and edited with your wifi and Thingsboard information.
I've added a fudge factor value to the altitude sea level configuration, so you will need to edit the value to get accurate pressure readings.
I mounted the whole thing in a waterproof enclosure with holes drilled for air intake, and it's given me steady performance for 6 months at the time of this writing.