It doesn't "vacuum" the floor. Dust that has already settled on your furniture is too heavy for the purifier to suck in.
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: should i buy an air purifier
You’ll need to replace filters every 6–12 months. Check the price of replacements before you commit to the machine. It doesn't "vacuum" the floor
Air purifiers work by moving air. If it’s too small or underpowered, it’s just a glorified paperweight. Pro-Tips for Buying: should i buy an air purifier
Avoid "HEPA-like" or "HEPA-type" filters. Look for "True HEPA" (H13) which captures 99.97% of particles.