Eigenvector wrote:
I have just a basic question about the vents for my gas furnace.

There is one large vent that leads directly to the furnace main ducting -
its located on the floor and is probably about 18" x 30". What is the vent,
is it a return vent, a heater vent, or something else?


Hi,
Vent is where combustion gas goes(chimney). Duct is where hot air and
return air moves in/out of furnace. Also newer ones have fresh air intake.