Mouse Smell In Ducts Over 1 year now - will it sell?

6.2Superduty wrote:
The ductwork is inexpensive flexible tubing you can purchase at home depot. I would remove the underbelly to investigate further.

The OP hasn't said whether his heating ductwork is interior or exterior so obviously it's the former, as was the case in my own KZ Spree, then there's no need to remove the trailer's underbelly. Interior ducting runs along the floor, behind & through cabinets, etc, so it's relatively easy to swap out, much more so than underbelly ducting.