Bests & Worsts Reviews from Amazon

I bought one of these to measure the indoor and outdoor air quality at my house. The readings were significantly higher than the state measurements and the PurpleAir meter that were by my house. When I put this directly on the output of my air purifier, it read a PM2.5 reading of 20, meaning my purifier wasn’t catching anything. I had my doubts about that, so I bought a second of this same meter. The second meter read consistently lower than the first, considerably lower. It would give a PM2.5 reading of 2 when the other was showing a PM2.5 reading of 27. And, the PurpleAir meter near my house was saying 10, so right in the middle. I can’t trust either of these meters and have returned both of them.