Review on Portable Airthings Corentium Home Radon Detector 223: Lightweight, Easy-to-Use, USA Version, pCi/L by Bob Vulpes

Opened the box and pulled the plastic tab as instructed. After about a minute during the calibration step, I got "ERR 518". I reset the block and the same thing, 3 times in a row. Replaced the batteries and this time I got the code "Err 4" and "Err 6". Seems like others are having this bug after years of use. So so far I've either gotten DOA or one that was returned and sold as new. Return and buy another. I'll update when I get a new block, but spending $200 on a block like this and getting a DOA casts doubt on the quality control and potential accuracy in that regard. **UPDATE BELOW** I have purchased two more units. . Both work fine this time, but one of the devices has blisters on the screen from the protective film and the battery tab is missing. AMAZON SELLS USED DEVICES AS NEW. I ran both blocks side by side in the basement for 3 days and got completely different readings. See second photo. You would think that on $200 devices there would be quality control with more accurate calibration. How the Amazon comes back without realizing it, or why the blocks aren't sealed to indicate they were actually opened.