I've had this air filter for about 1.5 years now and it really makes a difference! I leave it in my bedroom, which is a fairly small room (about 12' x 12'), but I bet this would work well in larger rooms too. I have year-round allergies, which is the main reason I bought this air filter. It really does seem to help with my allergies and it does reduce any odors (from pets, foods, etc.). I'm a nonsmoker, so I'm not sure how well it works to eliminate smoke odors. Overall, I would highly recommend this air filter for those who suffer from allergies!