I understand that. Ours were pressure washed out, then Filled with dirt for a few weeks, then dumped and pressure washed out again. It took out all residue, and we let them "cure" for awhile after. But that was for dogs, probably less sensitive thank chickensThese are Food Grade.... I feel better with them. We actually had SEVERAL show up after the flood, but most are filled with oil or grease. Hubby said I could have them, but I don't really think I want to use them for chickens..... just creeps me out a little too much.