around here we sometimes get the smell from dairy farms and cattle feedlots in the spring when things first warm up. a few years ago the Farm harvest contractor Did not use a moisture meter when he baled our hay too wet and after a couple weeks the spontanious combustion was starting and some bales started smoking. He had left his big forklift loader and I was able to spread the smoking bales out in the field and they cooled down and the smopke stopped