You can make a homemade carbon filter for $25- may not work as well as the commercial variety, but can help you save some cash and still get pretty good odor control.
I have co2 filters on inline fans in both of my tenst wanted something for the room for another odor barrier and wanted it to circulate and clean air I was wondering if those air purifiers work to filter the smell or more just bacteria and germs adn whatnot