This Medium Room Air Purifier is so efficient! I used it in my family room, which is slightly larger than suggested but I felt like that was a space that I needed purified. It is so quiet that it didn't interrupt any conversation or tv watching, which was great for my young daughter. While the effect wasn't immediate, I definitely felt a difference when I left to go to the store and then came back into the room. After having it running for a while, I noticed a difference in  my own breathing and felt miles better. This is such a great product!!!!