Not the OP, but I've been using a model by Awair for a while now (looks like they've released a new product that's a bit more expensive since I got mine). I wo

Not the OP, but I've been using a model by Awair for a while now (looks like they've released a new product that's a bit more expensive since I got mine). I work in a very small office shed, and if I leave the door and window closed tight it will quickly get over 2000 ppm (45-60 min). At that point I'm typically feeling more tired, and a bit foggy. By keeping the window cracked I can keep the readings down in the 800-1100 range, and I feel much better.