I am really into preventing health issues and like the idea of DE to protect against mites, lice, worms, etc. I do put ACV in my girls' water but when I sprinkled the DE in the coop and raked it into the bedding the air in the coop was unbearably dusty. MY sinuses really hurts and my friends eyes started watering badly. The girls started sneezing. I ended up removing it after 6 hours. Pretty much immediately after that my 9 week old Wyandotte who has malformed sinuses (you can watch her breath puff out under her eyes) started sounding like a creaky gate swinging in the breeze -- her peep was/is now like a metalic squeak. I took her to the vet (waaaay ridiculous I know) and she flushed the girl's sinuses. She checked out the fluid under the microscope and found lots of debris -- pollen, dust particles but only found a little bacteria. The vet told me to build a coop just for her and keep her on shredded paper bedding -- she was eating the pine shavings. Okay -- NO WAY!!!! We just worked on our coop for two months. It's primo! We are not going to build a new coop and separate Maude from the rest. She would be miserable and so would we. We were trying the deep litter method but now because of the pine shavings issue being hard on Maude we are using wheat straw (she doesn't eat it as much) and are changing it every week. I put DE in a little sand box that also has topsoil in it with hopes that the girls would dust bath in it outside where the dust dissapates unlike inside the coop. They don't dust bath there -- preferring to do it in a spot elsewhere in the run (dirt floor for now as they have only been in it for a few weeks and are still eating the remaining grass -- I will be adding sand soon and maybe try the tilling methods in one area). Should I be sprinkling it on the floor of the run? How much is safe???