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.

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.

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.

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 calibrated and followed the instructions fully. All measurements were made to typical scientific standards, as someone lab-trained would do, and with knowledge of how this measurement device works (fan blowing air through sensors, ideally in a still environment, and taking a while to settle).The TVOC measurement is junk. I compared it between fresh air, indoors, and right next to salmon being pan-fried with diverse heavy spices and emitting a huge smell. It reported 44, 50, and 42 ug/m^3 respectively, when the true TVOC measurement was above 1000 ug/m^3. Only special circumstances were able to bring the reported measurement up, to 120 ug/m^3. Most tested industrial solvents do not cause any response, even in stifling concentrations. I was curious how a TVOC sensor might work, but this one simply doesn't. It's not usable even for relative comparisons. This device is measuring nonsense.The PM2.5 measurement is junk. I compared it to reference monitors in my city. The reported result varies between 2-3 ug/m^3, completely contradicting the reliable results from many other monitors that use multiple sensors to cross-check each other. It doesn't detect relative variation either, being stuck at 2-3 ug/m^3 in all environments. There exist cheap and reliable PM2.5 sensors, but this isn't one of them.The formaldehyde (HCHO) measurement is junk. No valid formaldehyde handheld sensor has ever existed in a device under $500. Measuring formaldehyde is very difficult, and other consumer devices will similarly fail.The humidity and temperature sensors work accurately.This is a re-branded device, and there are many identical copies of this with the name switched out. Both the identical copies and the similar models use the same sensors, and they will have similar failings. I strongly regret buying this. Of formaldehyde, TVOC, and PM2.5, the only possible consumer sensor under $500 is PM2.5. There do exist cheap and reliable PM2.5 sensors to purchase. For VOC and formaldehyde measurements, you will need to contact a scientific lab for a test kit (adsorption tube method) at $125-300, for a one-time measurement.Apart from the sensors, the software and design are very good. The fan placement is well-thought. The device is well-balanced, and can be laid on a table with the intake in the air and the screen readable. The instructions are understandable. The calibration tools and fan control are good features. The UI is convenient, although the recording feature is unusable because all values are at the bottom of the graph and cannot be told apart. The packaging is similar to a high-end phone. This would be a very good device if its sensors worked properly.