Is my furnace a direct vent or power vent?
where the flue goes into the furnace, can you look up into the flue from an open space in front of the furnace or does it go into a blower-ish looking object? if you have the 'shelf', thats a draft diverter and you have a natural draft. blower object, you have induced draft. if you have pvc flue[s] you are sealed combustion induced draft. thats about all resi has to offer in venting unless you have a vent free fireplace or the like.
edit: also the inducer is the 'power venter' but natural draft just uses the thermal energy to vent