Decades of settled dust in original sheet metal ducts
Why it happens here
Homes built before the 1970s in Art City North and Art City South had no real filtration. Dust, pollen, and construction debris settled into the bottom of the trunk line and hardened over time. Standard vacuuming will not break it loose.
Our approach
We agitate the duct walls with a rotary brush duct cleaning machine and follow with a HEPA vacuum. On the worst runs, we use an air compressor to loosen packed debris first. The result is source removal, not a surface pass.