I have two of these running right now. According to my air quality meter, PM 2.5 has fallen from about ~250 indoors to ~40. (My meter shows ~600 outside, which is about 3x what the government website shows for my area)
Government website most likely using an algorithm that pools data and takes into consideration multiple readings, sometimes lagging by a few hours. Your sensor gives the instant value in your immediate environment (assuming it is well-calibrated and installed outside of local influences such as kitchen fans, dryer lint etc etc)
I'm not sure how accurate it is or isn't. It reacts to the filters, for example, or if I hold it in front of the filter it'll reach a very low number, conversely if I take it to other parts of the house or outside it'll increase. I've done a few trials like that and it seems directionally accurate, but I can't speak to the numerical accuracy.
It measures PM 2.5 and 10 and has a button to show graphs over time for ~12 hours. Battery life is pretty good, I usually leave it detecting on the charger, but I've had it in handheld mode for several hours and stayed above 80%. It's super simple to use.
One thing I don't like about it is that it has a cheap plastic hinge that is supposed to let it stand up, but it broke on me after a couple uses. It doesn't seem to matter though if it's standing up or laying down, it still reads pretty much the same.
I wish it had a way to export data to my computer or maybe an app.
