The Conair Pure brand air purifier works very, very well. I placed it in my bedroom as I've been having allergy symptoms for months. After the first day I could feel the difference in the air in my room. It felt fresher and even seemed cooler. 
I ran it on the lowest setting and it is silent, when I tried medium or fast setting, there is a soft running/purring sound. 
I would definitely recommend this product, and the price is very reasonable.  I did receive this as a promotional product but I planned on writing an honest true review.