How do I determine what air purifier I need based on my room size?

Small rooms, often below 100 sq. ft. may only require a tabletop or mini tower-style air purifier to circulate the air. Medium rooms that range between 100 sq. ft. and 170 sq. ft. will typically need a floor model that has a larger filter to effectively process the air in the room. Large rooms, over 170 sq. ft. will require a full size tower or box style unit. Most air purifier cartons and descriptions offer specific information on room size or square footage covered by the air purifier.