Air Purifiers
some with HEPA filtration. HEPA filters are expensive.
Hunter Hepatech series(pick any, such as the 374 floor model), available from airshack $95
cleans faster than a quadra. 30930 filters for the floor model also available from this vendor and are $22 each, but are also available in 2, 3, 6-pack. replacement carbon pre-filter 30901 for the floor model is $22 for 2-pack, but is available in 3, 6-pack.
Oreck XL Air Purifier (black or silver), available from oreck $369.95, tower $599.95
seems like there are a lot of different filters to buy. also seems like it does a good job in a demonstration with an enclosed box. Cleans a room 5x/hr. moves the air in the room. kills germs etc. in the air. converts ozone to oxygen. removes VOC's. water-cleanable filter plates.