Get a few HEPA air filters, one for each room.

I have this one and it’s great ($100): https://smile.amazon.com/GermGuardian-Purifier-Allergies-Cleaner-Guardian/dp/B01CTN024Y/

I got my mom this one and it’s even better ($170): https://smile.amazon.com/gp/product/B01728NLRG/