It's not a huge amount, a stain over about 18" square. Probably was there a day or two before I came across it. I swept hay chaff on it in the hopes it would soak up the smell. I store beekeeping stuff and the winter hay in this building, 10' x 16'. I've left the door open (spill is right inside the door) windows are open, too. Suggestions? It has a wooden floor.