Make a decision
PVC vent inspection versus duct cleaning
One scope
PVC intake/exhaust pipes carry combustion air or exhaust for applicable high-efficiency appliances.
The other scope
Supply and return ducts move household air through rooms.
A concrete example
One pipe terminates outdoors with combustion gases; the other distributes room air. A salesperson who calls both 'ducts' should identify which line item touches which physical path.
Which question settles it?
These paths have different hazards and must never be conflated in a quote.