I recently purchased the 45i out of necessity. I came home and had a reaction to the air in my bedroom. My eyes were itching incessantly and my throat was getting tight. I ended up ordering this purifier that night and sleeping downstairs on the couch until it arrived. The day I got it I put it to work and it scanned the room. I ran it on high for a couple hours like directed and have left it on auto since. I no longer have the reaction and sleep soundly knowing it's taking care of any allergens in the air. So grateful for this purifier!!