Air Purifiers For Cockatiels?

I would like to know if anyone has a favorite air purifier that they use for their birds. I have cockatiels that are very dusty and sometimes their nostrils get clogged and inflammed. I try to spray them the best I can, but they are not always co-operative. Someone had mentioned to use an air purifier to help with the dust.Do they emit any chemicals I should be concerned about? Is one better than another or are they all basically the same? Any and all help greatly appreciated. Thanks!!!!!!!!