111:3 A person must search all the rooms where chometz might have been brought, including basements, attics, storerooms and woodsheds. We must also check any containers in which chometz was kept. Before the search, one should sweep out all these places and remove all chometz from them so that they will be easier to check.
111:4 A barn and a chicken coop where one puts grain for the animals do not require searching because the grain does not become chometz in these places. If you want to say that maybe it will leaven, then we say that maybe the animals will eat it all. (There are two doubts, so we act leniently.) However, if one feeds them grain that is already chometz, then there is only one doubt – whether or not the animals will eat it all. In a case of one doubt, we act stringently and one must check. (The Magen Avraham says that if the animals were not fed chometz for the preceding 30 days, then the barn need not be checked – Mishnah Brurah 433:27.)