Air enters at the top or bottom of the unit and is discharged vertically out the bottom.

a term used to describe the top to bottom airflow through a furnace

Refers to a type of air conditioning system that discharges air downward, directly beneath a raised floor, commonly found in computer rooms and modern office spaces.

A term used to describe the direction of airflow through a furnace. A downflow furnace takes return air from the top, heats it and then delivers the warm air from the bottom

A type of furnace that takes cool air from the top and blows warm air to the bottom.