Since about early April once the weather started getting a bit warmer here in NY I've been smelling a urine-like odor coming from the heating vents in my home. We rent a two floor house that is built directly on top of a huge rock. OUr basement looks like a cave! Anyway, the basement smells moldy but doesn't smell like the urine-like smell. The landlord had the vents cleaned in in the beginning of March. I've checked the furnace and its pretty clean down there and no odor seems to be coming from there. I'm stumped. If its mold in the vents, what's the best thing to do? I know bleach usually kills mold but is it safe to spray it in the vents? By the way, the house is pretty old, pipes are more than 40 years old. Can some someone help?

Cats or kids?