I purchased the 75i and 45i from Alen and believe it is making a difference. The first night my husband and I commented that we think we slept much better with the 45i in the bedroom. We don't notice any smell but then as explained to me by Amanda, clean air doesn't have a smell! I have removed the filter on both units and do not see any debris in the filter which I was told that I would noticeably see. Not sure why I don't see anything on the filter but I don't. The units are quiet and not at all the noise level I feared. I put them both on turbo in the beginning but backed off the speed after a week.