Have you compared the Sensirion SEN55 against the Plantower sensors? I ask because I’ve recently picked up both and have played around with them each individually but haven’t compared them for accuracy yet. The nice thing about the SEN55 is that it contains all of the sensors in one unit (PM1.0 to PM10.0, temperature, Relative Humidity, NOX and VOC).

They do cost a little bit more than the Plantower units, about $30-40USD. For anyone looking at the Sensirion sensors, be aware that the SEN5x products span a range, and only the SEN55 has all of the above sensors in one unit. I’ve found the Sensirion software to be pretty nice to work with. I was able to port their embedded i2c example repo to ESP32 with little trouble.