Basement Ammonia Smell
Our 1920 Colonial had two additions built on in the 30s (I think), changing the footprint from a rectangle to a shallow 'U'. For the first addition, they broke through the basement wall, dug a crawl space (about 5' deep from the surface of the surrounding lot) and built the addition on top of that. The floor of the space is bare and very uneven dirt, and it's quite clear that someone in the past used the space for trash storage. The other addition had a full-depth foundation dug, but that floor is also bare earth. This second space is behind a door. (This is a very spooky space. I keep wondering why there is a hasp on the outside of the door!) The first still has a wide-open hole in the basement wall that a PO chicken-wired off to keep his kids out.
The basement is otherwise pretty dry and ordinary. It smells a little musty and it's very cool; I suspect that the hot humid air that we've had for the last few weeks isn't helping the situation much.
In the half of the basement where the open crawlspace is I can smell a kind of sharp ammonia smell. I associate ammonia with urine, but I suppose there could be other causes.
Any ideas where it might be coming from, and how to get rid of it? How would you neutralize an ammonia smell?