The Honeywell True Hepa Air Purifier seems to work well but it leaves an odor in the room. I have not been able to identify the odor (not sure if it is carbon). I've run the filter a few hours a day for many days. The odor is bothering me so much that I find that I don't want to use the air purifier, making it a waste of money for me. Also, the noise is too loud to run at night, even on the low setting. Honeywell states that the True Hepa Air Purifier has an activated carbon pre filter to capture large particles and help reduce odor. The True Hepa filter captures particles as small as 0.3 microns, Surroundseal technology to help minimize air leaks, and a powerful fan motor to draw in room air and release cleaner air 360 degrees. I recommend that you run the air purifier all day for 1 week after you buy it and if you find that there is still a noticeable odor, return the purifier for a refund.