A cheap, cost effective method [ under $50; £28.52; �41.56 ] is the Holmes Odor Grabber. Carbon filter with a secondary carbon sheet over that; built in air ionizer [ four pins in the exhaust ] to get the smaller shit, and turns the air pretty damn well for the size it is. Manufactured to run 24/7 so you needn't worry about turning it off, or giving it a break. You can check it out below.

http://www.amazon.com/gp/product/B00...lance&n=284507