Air Quality Detector Indoor for Accurate Testing Formaldehyde(HCHO) Monitor, Air Quality Tester with LCD Display and Alarm for Car Outdoor Detection by Moonee.

I give this five stars even though, as one reviewer noted, the Formaldehyde and TVOC readings don’t seem reliable. I am only interested in PM2.5 levels, and this device gives PM2.5 readings that are realistic, consistent, and seemingly accurate (I have nothing to compare them to). I live in northern California where, with wildfires raging, the air quality varies from good to hazardous. I want to know specifically how bad it is in my neighborhood AND inside my house. This device tells me, quickly, easily. The readings it gives for the outdoor air match the weather service. The readings it gives for inside my house are consistently approximately half the reading of the outside; it shows that my air purifier (Guardian) can improve the air within minutes---but that purification of a closed room lasts only 3-4 hours. It tells me which room is relatively cleaner. I found the device easy to set up. You plug it in (cable provided) to charge it for a few hours. Then you calibrate it (directions included). After that, you simply turn it on, wait 3 minutes for it to warm up, and take readings. With the English, there are some Chinese characters, both on the device and in the manual, but it’s not hard to figure out the functions of three buttons. The readout is clear, with units in µg/m3. Highly recommended.

I have no idea what the read out means. Poor use instructions.

Out of 5 different Air Quality meters (Temtop, Igeress, FooBot, Perfect Prime), this one is the worst. HCOH reading is O.001 when the others read much higher. Basically, it's worthless

It is not easy to understand no explanation of what the numbers mean

I brought it on the other Chinese shopping website, the reading on this device is totally inaccurate, and its battery life is a JOKE. this device is pretty much junk.