I purchased two units, they work great.I have cleaned the pre-filters twice and they are still doing the job. I have 5 cats and three dogs and you can't even tell I have animals, they work great for smokers also really takes the smell out if you turn on auto and go to bed. When the unit is on high you can feel the air moving around the room, with two units on high its a little loud, but run them on low or med you can hardly hear them. The units are very nice looking also, they are big units so you need a good size room or space for them. They are a little pricey but you get what you pay for. I'm just hoping the main filters last more than 8 months before replacing. I'll let you know