After reading lots on here I decided to put a small swimming pool and a few inches of ash, dirt and a little of my wood shavings in it for dust baths. The chickens love it but there is a coat of dust all over everything in there. Even the eggs when I pick them up are dusty. I know it is suppose to help with the mites and lice. I do have 2 windows in my coop and so I know there is some ventilation.