1.   Air is heated and then circulated through large ducts to all parts of the house.

2.   Back-seat passengers also have their own large heating ducts and polished wood writing tables that fold from the back of the front seats.

3.   In your system is a large duct where hot air is stored, with smaller, round ducts coming off it, leading to the rooms.

4.   These smaller ducts should have dampers near the large duct.

5.   Hunter said there was a warren of tunnels under the house, primarily large ducts for the heating and electrical systems.