What is the best air purifier for cat litter smell?

Best overall for cat litter smell: Austin Air HealthMate Plus. It is the strongest pick if odor control is the priority because it uses a large carbon/zeolite filter blend, which matters more for litter-box smells than HEPA alone.

If you want a more mainstream smart-home style purifier for a room with a litter box, pick the Coway Airmega 400 or 400S. If you want a cheaper option, the Winix 5500-2 is a solid value because it uses a washable pre-filter plus a real carbon filter, not just a thin deodorizing sheet.

Important: no purifier will fully fix litter odor if the box, litter, or ventilation is the main issue. Put the purifier in the same room as the litter box, run it continuously, and prioritize models with substantial activated carbon. HEPA is great for dander and dust, but carbon is what helps with smell.