VSON Air Quality Monitor Indoor, Formaldehyde Detector, Air Sensor Tester Pollution, with HCHO/TVOC/PM10/PM2.5 Real-Time Data Colorful Screen & USB Charging(Gray)

Nice! Works well, easy to use and understand. Would recommend.

With lots of smoke in the air last summer, I ordered a Purple Air meter, but there was a long delay in getting one, so I ordered this meter to use in the meantime. Now that I have both meters, I can see that the Purple Air meter generally agrees with other nearby meters, but this VSON meter does not agree. That leads me to think that this meter is not accurate, so I won't be using it any more.

I'll show you four groups of results i tested in 20 mins. (I turned off it and turned on again.) I don't know which one to believe.

In wonder if I got a unit that had been sitting in a warehouse for a few years? I just got this a day or two ago, and found the battery running low very quickly. So this morning I recharged it so the battery showed 5 bars (max) and made a note of the time. Exactly 2-1/2 hours later that battery icon showed zero bars --- an icon of the battery with a diagonal line across it. Ten minutes after that the unit shut itself off, battery out of juice.Overall the unit seems to work fine, apart from the poor battery life. I guess I could keep it and use it in an always-plugged-in manner, but I want to be able to set it outside of a glass door on relatively poor air quality days without having to recharge it constantly. And ... the stand for it is kind of rickety, it tips over easily. Connecting to a plug makes it more difficult and tedious to try to get it to aim the screen (so that it stays aimed) at where I want to look at it from.So I will return this.A couple of other notes ...I bought this at a point of low outdoor air quality. The calibration instructions are to take it outdoors to fresh air --- clearly not an option in this case. Not a fault of the unit, just an FYI.And ... I wonder how long such units last? I know that smoke detectors in a home should be replaced every 7 - 10 years because the smoke detecting sensor is no longer reliable past that time. Which suggests to me that something similar might be the case with this unit. I have no particular knowledge here, but I suspect that this isn't the sort of thing you can buy and just expect to keep working for years and years (independent of the internal battery. It would be nice if there were some information from the manufacturer about that. Along with, perhaps, any ideas about how to calibrate such a unit relative to any sort of known-to-be-accurate reference for PM2.5 in particular.

I charged the unit as required and then calibrated it as required. !/2 hour later it was totally dead. I could not get the display to illuminate after charging as indicated in the instructions. I WANT MY MONEY BACK!

I have some experience with these consumer monitors. I bought a Dylos a few years ago and used it in China, and I calibrated it according to air quality monitors that the government publishes in both Silicon Valley and in China. I left that one in China, so I bought this one to see if would work.Nowadays, purple air uses the same type of pm2.5 sensor, and after looking at pictures of it, the sensors look identical. It's the same sensor you can buy separately from Adafruit - but you'd have to connect it to a controller to get it to work, and then CALIBRATE it. Again, the sensor in the VSON, the purple air sensor, and the Adafruit component look identical.I paid the premium for this one (the bare sensor is about $40) thinking that I'd be saving the trouble and calibration. While I did save the trouble of getting the sensor working, it's "not as sensitive" as the purple air. That means, when purple air (ALL sensors surrounding my home) reports 30 ug/m3, the VSON is showing something like 20 (roughly 2/3). After calibrating with many samples over a day that ranged from AQI 20-150, I now have a calibration curve. That means I read the VSON, look at the curve, and get a pretty good feeling for the REAL air quality.I suggest this for anyone who buys it. I sort of expected I'd have to do it - now I just regret I could have bought a cheaper one and done the same thing.