strange sweet smell from air vents
A strange sweet smell comes from my master bedroom air vents during the winters. I hired a duct cleaner, but the smell was still there. After a year of not being able to determine the cause of the smell, I cut some holes in the floor of the bedroom to see the air ducts underneath. The space under the floor really smells of that sweet smell. I have no idea where it is coming from, except that a neighbor's bathroom is underneath and perhaps some air freshener is seeping through. Nevertheless, the duct system must have some leak for the smell to get in and then come out of the vents. There is a main branch of the duct, from which three flex ducts come out. The joints between the main branch and the flex ducts have this "alternating tabs" design, where each tab goes inside or outside of the main duct. There is no taping. Do you have any ideas on how the sweet smell is leaking into the duct system?