13-in-1 Air Quality Monitor Indoor with Beep Alarm, 6AQI Air Quality Detector with PM1.0 | PM2.5 | PM10 | Temp | HUM | Formaldehyde | VOC Tester for Home Office Plant (Ink Grey)

Two stars for nice packaging. Pretty box. Battery charged fine in about an hour. Does not power on. Held button for 3 seconds or more as per included instructions. Nada. Nothing. Blank screen and no sounds. No plastic screen protector. Screen has very fine scratches indicating item may have be used before. Printed return label.

There are separate areas that display the measurement value and level for every air quality. When it measures the PM2.5 level in the air as 60, a green block is shown. If the value is 190, exceeding the safe range, a red block appears. I really like this air quality, I don’t have to constantly remember the numerical range—I can just look at the colors to make a judgment.

I noticed it has a built-in lithium battery that can be charged via USB, allowing for long usage after charging. I don't need to keep it plugged in, it can be placed anywhere.It measures air quality in the bedroom, kitchen, school, and office, and can also be used in my plant sunroom. Overall, it’s an excellent value for money.

I followed the instructions in the manual and started the detector correctly and used it, it was very easy to use and I am glad I purchased it. The manual says that the device will sound when the HCHO concentration exceeds 0.120mmg/m3. For this reason, I went to my newly renovated house to test it and sure enough the detector made a sound and the detector was accurate. The instruction manual also lists the air quality standards, making it easy for me to know if the tested air quality is good or not. It's really value for money for me!