The previous tenants had a lot of dogs.
I never met them, so I don;’t know how many dogs or what kinds – but they must have been giant, and very hairy. When we moved in the backyard was wildly overgrown and filled with “stink bombs.” That is what we called the mess the dogs left behind. It took a few days with a shovel and a bucket to collect all of that waste. That was far from the worst part, however. At least the dog mess was outside, but inside the years worth of dog hair and dander had infiltrated the ductwork and slowed down the HVAC system. Although the house itself had been cleaned, the landlord had not gotten the HVAC system checked out. The result was a series of air ducts coated with massive amounts of fur, hair, and dander, to the point where the whole house still reeked like dogs! My first instinct was to start scraping out the inside of the air ducts myself, but my wife suggested calling a professional. I am glad I listened to her, because I found out that I might have permanently damaged those air ducts. The HVAC tech showed me how the ductwork was very old and brittle in places. Had I gone in there scrubbing and scraping I would have put holes in the sides of the air ducts. He recommended buying the “deep clean” ductwork cleaning package, and he guaranteed that the indoor air quality would improve significantly. He was right, and with clean ductwork the house no longer stinks like animals.