I had a Trane system installed one year ago. The duct work is 20 years old and is fiber box trunks and foil flex from the trunk to the vents. There are three returns, one 10X20 and two 20X20. Only one is high in a room near a ceiling. It is a new return added with a big flex tube to the fiber trunk under the house going back to the system.
I have noticed a lot of dust since the new system was installed and I crawled around under the house checking for leaking seams and peeling tape. Still dusty.
I have asked the installer for help and he suggested using a new-to-him computerized gadget that requires sealing all the vents and the returns and measuring the cfm. Then is something doesn't compute as normal, he uses theatrical smoke to infuse the system and check for leaks under the house.
I guess this would help identify if there are leaks allowing dust from under the house ( ground that is mostly covered in plastic sheets).
Maybe this dust is normal and not unhealthy for a house that is more than 100 years old. I just don't know.
Any advice would be appreciated.