I need HELP with a Timberland DM48 1980s model

[BRamm]

I recently purchased a home that has a Timberland wood burning stove fireplace. The stove itself sits on concrete slab. The inner structure of the chimney is concrete block with a concrete slab just below ceiling level above the iron grating which the stove pipe runs up and through. So it seems that the heat from the stove itself is pretty well contained and distributed to the rooms in which it sets. It is two sided.. It has an intake pipe running from the crawl space for fresh air intake. Recently I notice a 4” galvanized pipe built into the concrete slab above the unit with a reducer poking into our furnace room with shares the wall of the fireplace. Last time I was burning I had noticed a cool draft but didn’t check later if it started pushing warm. I’m hoping to find some guidance to if this may be for warm air distribution. We are in NW Ohio and the home was built in 1983.