Make a decision
Furnace cleaning versus duct cleaning
One scope
Furnace work names cabinet, blower, burners, coil or other equipment components.
The other scope
Duct work names supply and return trunks, branches, grilles and access points.
A concrete example
A fan-wheel photograph is evidence about the furnace, while chunks emerging from one bedroom outlet are evidence about a branch. Ask the bidder to name which of those paths their price reaches.
Which question settles it?
Compare the component list in each estimate; neither label automatically includes the other system.