I have a service manual but some details aren't quite clear ... helps to have a unit to examine, I imagine.
There's one exhaust duct at the rear, as standard for the lower tumble dryer.
The upper cabinet has a separate blower and an electric heater/steamer unit with water jug. It can be operated in heat-only mode or heat/steam. Choice of Low (140°F) or Ex Low (110°F) temps. Also has an Add Fragrance option. The instructions state only tap water in the reservoir. A separate "caddy" is for a dryer sheet so presumably that's the source of fragrance, maybe there's a duct-door that opens with Add Fragrance to pass airflow through the sheet. There's a vague reference that it exhausts out of the upper door. Specifications state the airflow rate is 80 CFM for the upper cabinet (170 CFM for the tumbler dryer section).
Upper cabinet and lower tumbler can be run separately or simultaneously.