Review on 🌬️ KT-401 Mini Air Ion Tester: Accurate LCD Display of High +/- Air Ion Concentrations by Leonard Beard

Never thought it would actually work but it worked. You really need to take the time to find out, but it's actually worth reading. It must be in close proximity to the device and not read through walls or cabinets. I tested it on both of my room air purifiers and got readings between 14 and 16. I have no idea what the reference is, so all I can say is that the air purifier produces ions. But that's all I really wanted to know anyway. I removed the panel from my home air conditioner and again got a reading of 1400-1500. I don't have a reference point, but I know the ion generator is working, which is what I wanted. For $50 not thousands per meter this is a winner.