NEZEAir quality monitor, USB charging multifunction TVOC detector for PM1.0 PM10 for CO2 TVOC for HCHO PM2.5 Black (NEZEUmxI-11)

I found this to be great and it even caught rising pollutants before I could detect it with my nose so I was able to take immediate action to air out my place.Reading up on each of the sensors are a must as identifying what to correct requires understanding what seems to be wrong. So far seems great.Battery only seems to last a few hours so I have it plugged in constantly.

Excellent display which can show all readings, or re-orientate to show either pm 2.5/pm 1/pm 10 or HCHO/TVOC.The pm 2.5/pm 10 seems accurate when tested against a Temtop mobile meter. The temp works ok around 23 degC but is wildly inaccurate, under reads, at higher temperatures when tested against other devices.But if you want a pm 2.5/pm 10 reader this seems fine.Incidentally i have tried the Temtop in London and in the Berkshire countryside and the only time I have seen high readings is once during June when it rose to 26 and Sadiq Khan gave an air quality warning, but that was from a Saharan dust storm. I bought this because i was told we have a man made air pollution problem especially regarding pm 2.5, this is clearly nonsense, neither of my pm 2.5 readers move much above 4 at home or in central London streets.

I have Airthings View and Carbon Dioxide Monitor NDIR Sensor and they all work... This one measures absolutely nothing.CO2 for example on both of my devices are around 1000 to 1100, this one is always 413 to 420... I open the window, its still 413 to 420, others have already dropped to 600 to 700... I close the window, my other are at 1300, this one is still 413 to 420... the only way to get Anything, is to spray dodorant near it or blow into it and it will show you like 1800 CO2 reading... that is pretty much it...bottomline, completely useless... which is a pitty, cause its compact and easy to read... would be nice if the sensors actually did something...

Does what it says on the box great

Not mentioned in the main features but it has a siren that goes off if the levels get beyond what are officially considered dangerous levels - at least for PM2.5. Pressing the button on top slightly longer time than a tap puts it in mute mode though so you don't have to have it on. A quick tap changes between Celsius and Fahrenheit, and putting it on its side/end (from horizontal to vertical or back) changes the display from a simpler one to the more detailed one with the TVOC and other air quality measurements. It does need quite a loooong press (several seconds pressing the single button down) to turn it on or off though, which is a touch annoying but they decided to minimise costs and stick to just one button to do everything (plus the which-way-up sensor). Quite like it overall.(that siren was when we accidentally burnt some bread the other side of the long narrow room and it went off recently, while the device was sitting on the floor, on normal display. PM2.5 levels seem roughly in line with another meter I've had that just measures those (and that small pocket-sized smoothly-curved one agreed approximately with reported levels on some underground tube train lines here in London).Temperature seems accurate enough around normal room temperatures and probably not too far off when left outside on a very cold wintery night (intentionally for a while), but of course it takes a while to cool down to the ambient temperature and give closer to accurate reading just like any other thermometer of the same type of design (ie. one not relying on direct IR from the subject or something else).