In the Chicken Health Handbook by Gail Damerow she says on page 15 in a discussion of alternate forms of litter for use in a coop that "[h]ardwood shavings, on the other hand, should be avoided due to the danger of aspergillosis." No other or further information is provided either supporting or explaining this caveat. Is this generally accepted wisdom? And, if so, why? Any information on this subject would be appreciated Hugh D.