[crazygringo]

Something would seem to be wrong in your situation then, just one should be enough to get it to green if windows and doors are closed.

Not sure if your filters need to be replaced, if you need to wipe dust off their exteriors, or something is just wrong with their airflow that they're not filtering.

A $100 Levoit purifier (the longtime Amazon bestseller) has been keeping my bedroom in the green (measured by an Awair) while it's been maroon (400+) AQI outside today here in NYC.

[29athrowaway]

With those you have to vacuum it every 2 weeks and change the filter every 6 months.

[bagacrap]

Changing a filter every 6 months sounds more than reasonable to me

[29athrowaway]

Yes. Just saying that the filter is not simply an appliance that runs forever.