A couple of weeks ago ,we were coming home from a trip. We noticed that the we were getting a very noticeable smell from the Black Tank. We stopped to get breakfast and a cup of coffee. We saw that the vent with the automatic fan over the cab-over bunk had come open,(don't know how being as we don't use that bunk except for storage) When we went back to the RV we made sure all of the vents were closed. All of the vents including the one over the cab over bunk. We did not have any odor all the way back to the house.