Air Quality inside your apartment

[Nedrapter]

Considering the recent spikes in air pollution, I'm trying to improve air quality inside the condo. I'm not sure what's a realistic goal though, when it comes to PM2.5 that is the main pollutant here. Those who keep indicators and air purifiers inside your house, what's your acceptable levels? The WHO suggests pretty low values that I don't think I've ever seen inside even when using the purifiers.
I recently also had some respiratory issues which makes me worry more about it.
I've also not sure what device to trust... My air purifier shows 15 μg/m3 while an AQI monitor that is exactly next to the purifier shows 35  μg/m3 (PM2.5)

[KhunLA]

With our purifiers on, we keep the PM2.5 <5 most of the time.  Sometimes need the ACs to assist with that, sometimes not.

 

Only have 2 Xiaomi purifiers, and they handle 105m² with no problem.   House is fairly new build and pretty airtight.

 

Have a PM2.5 stand alone meter, and fairly accurate.  The air purifiers will auto cycle up & down at times, when happy with PM2.5.