Traffic pollution (NO2 and fine particulate matter) seeps into homes; a purifier helps scrub these outdoor pollutants. It might be a waste of money if:
A purifier can catch spores in the air, but it won’t stop mold from growing on your walls. You need a dehumidifier or a plumber for that.
Avoid "HEPA-like" or "HEPA-type" filters. Look for "True HEPA" (H13) which captures 99.97% of particles.