Had a similiar issue with my auto. Mice got into the air vent, how I do not know, but every time the heater was turned on the heated air was permeated with mice urine smell. Removing the nest did not clear up the smell issue but after using the following product it took care of the smell problem with just one thorough application. Even thou this product says for Ferret's IT DID WORK for my mice urine and is very inexpensive. Pet stores as was suggested is the best source but this site will ship. Nature's Miracle at
http://www.natures-miracle.com/search.aspx#/?filter.brand=naturesmiracle&q=5177