"Heating ducts" are pathways in a building that allow warm air to flow from a heating system to different rooms, keeping them warm and cozy. Full definition
[38] Along with a nearly invisible facelift, front side airbags were new options for 2000, as were larger wheels, four - wheel discs, and rear heat ducts. (en.m.wikipedia.org)
You can also opt for rear seat heat ducts, so your passengers can remain cozy, too. (taylorchryslerdodge.net)
Just place them on the arms and set the unit over a floor heating duct. (geekwrapped.com)