We have dealt with a very stubborn odor in our home that has come and gone for the past 5 months or so...we originally thought it was from one of children (who sleepwalks) urinating on the carpet because the smell was a very strong ammonia-like smell. After deodorizing and cleaning carpets, we found that the smell was not coming from the floor, but ceiling - and almost certainly from the air ducts in his room. We then thought the problem was due to a loose fitting on an outflow drain pipe on his bathtub which is in his bathroom off this room where the smell started. This loose fitting had caused water to leak onto the floor and through the ceiling below. However, after more investigation, the strongest source of the smell was coming from the bedroom - not the bathroom - and most certainly from the air vent. We have searched the attic and the duct for a dead animal and honestly - after five months, it would seem that if it was an animal, it would have decomposed by now.
To better describe the smell and the situation surrounding it: it is an ammonia/urine type smell. It is very pungent at night and on occasion, other times during the day but it is not constant throughout the day. It literally disappeared for a month or so and then it came back with a vengeance. It is so pungent that at times, it almost hurts to breathe in there and my son has to sleep downstairs.
Does anyone have any insight to this very bizarre mystery???