Review on Temtop Particle Detector Professional Accurate: Unmatched Precision in Measuring Airborne Particles by Bryan Fields

September 2020 update. This device has worked well and I am using it to monitor air quality during the ongoing California wildfires. Its outdoor readings match the official numbers pretty well, and I now think they're pretty accurate. If I move it from indoors to outdoors or to a room where I have an air filter, it reads about as it should. As I hinted at in the original review, the graphics mode isn't very useful. The peaks average over time. I mainly use it by taking it into a room or outside, turning it on and waiting a minute or so for the reading to settle down. What he shows is valuable. For example, my air filter reduced the PM 2.5 in a 15 x 15 foot room from about 90 to less than 20 in half an hour. After a few hours it dropped below 10. Likewise, opening the windows can quickly degrade the air quality. I will try this in my car to see the effects of AC. I also have a flow meter of a much more complex design, but I actually find it more useful for a number of reasons. PS I'm not far from San Diego otherwise AQI would be a lot worse. Write a preliminary review after 24 hours of use. This device, the P600, costs less than $100 and runs PM2.5 ONLY. (He claims to calculate PM10 but I haven't tried it and I suspect he's just using an extrapolation formula.) o He's fairly mobile. The size of a cell phone from the year 2000. The battery lasts at least a few hours and is easy to recharge. It was easy to transport, although of course if you put it in a briefcase the readings would be inaccurate. I carried it in my hand as I walked. It has 2 modes: current level and continuous chart. When you run the chart, it initially shows readings every few seconds. After a few minutes, he changes the scale to get less frequent readings. If you leave it on, there seems to be a band on the chart every half hour (?). o ACCURACY: This is a key issue. I bought a second counter (Awair) just so I can run them side by side, but I haven't run it yet. At this point I can only report that his statement is "plausible". In a clean and almost empty restaurant I got 7 (I think that's in micrograms per cubic meter). When I went home late at night it was about 16. If I left him at home overnight the numbers went down a bit. But there's no way to tell if these numbers are accurate, and I haven't pushed them into areas where I expect high readings yet. o Dislikes: There seems to be no way to get back his memory. I have to take a screenshot once a day to get a 24 hour chart! (This is a price to pay for a low price, and I knew it beforehand.) Likewise, there are no clocks. The only way to know WHEN the band was taken on the chart is to count backwards from the current time. If I leave it on for many hours, the chart will "average out" all the spikes. The only way to detect short bursts is to run it continuously. Maybe I'll set my phone to take pictures every minute. (I once read that scientists used 16mm cameras to photograph their instruments to get continuous data! That must have been before microprocessors were invented.) It starts at a setting of 1.00; If I change this value to 2.00 all readings seem to double. o Overall, it looks like a minimalist design that spends all its money on getting moment-to-moment accurate PM2.5 readings and minimalistic recording. I'm giving it 4 stars for now, but it's just a stub. I'll try to get back to you in a month or two.