====The experts recommend keeping doors and windows shut and use a high-efficiency particulate air (HEPA) purifier. “Undaunted (MFAS)” purchased one of these years ago and recommended we do the same. I didn’t listen then but I’m buying one now. Also avoid smoking, burning candles or cooking fried foods.===

Candles are OK. Fried food cooking is OK too if you use good active kitchen hood.

In my apts in Moscow I have active inflow breezers for ventilation in main room and bedroom + purifiers, all with HEPA filters. PM2.5 never is going above 1-2 longer than 10 sec. All devices are linked to smart home, CO2 is always below 1000.

Right now in living room (display of breezer):

33b57fb4-3fac-4d2b-92d1-ad931206b102.jpg