Review on 🔬 VSON Formaldehyde Accurate Pollution Measuring: The Ultimate Solution for Precise Formaldehyde Detection by Bill Russett

So yes I "calibrated" this twice - once outdoors and once indoors by placing it next to the HEPA filter. The reason I put "calibrated" in quotes is because such products are not calibrated that way. Real sensors must be calibrated by providing known inputs and determining values. It doesn't actually calibrate anything, or at least it shouldn't. That actually cleans the sensors. Calling it calibration is wrong. Above all, however, the device numbers are fictitious. He seems to discover things that he pretends to discover. I can put hand sanitizer next to it and the TVOC and HCHO readings will disappear from the charts. However, HCHO fluctuates between 0 and 0.188 mg/m3, which is the difference between perfectly safe and truly dangerous. The funniest reading was when after the first calibration the HCHO was said to be 0.6. In the street. The conversion to the more traditional ppm scale is 0.49 ppm. In the street. No way. No chance. That is even two orders of magnitude more than is possible under the open sky, even taking fires into account. Maybe it's just removing volatile organic compounds from the packaging. I'll give you the guess of the doubt about it. But what is definitely not certain are the other readings. It states that outdoor PM2.5 concentrations are measured in the single digits. Gauges less than half a mile from me in opposite directions read 45 and 46, respectively. It's definitely not 9. And if I add enough offset to get the number correct, then when I put it next to my HEPA filter (which should get the numbers into the single digits), the numbers just go down a bit the calibration offset, ie the problem is not that the device reports low by a fixed amount (±5% or so), but that it reports low about 10 times. In addition, the indoor humidity is displayed as 85% and briefly as 99%. The actual humidity in my house is 31%. The only reading that's likely to be correct is the temperature, and even that's about a degree higher, but I'm willing to give them credit for being reasonably accurate. Stay away. Far away.