Pure Air

I really haven't encountered an air purifier down here, I'm not to sure if they're a big thing, maybe they are in the states, like air-con. My understanding is that they take dust and what not out of the air, would be great for people with allergies I guess and you know sometimes in the morning when the sunshine is breaking through the gaps in the windows I can see just how dusty the air really is, it really isn't a pretty site and when I think about it I must be breathing that stuff in all the time.