Matt, that is not an exhaust system. You must all be city boys.
That is a grain elevator. If you look in the round pipe, you should see the auger that moves the grain up the round pipe (duct). That thing does not meet NFPA 96, but it does meet the GRANGE 96. But is is at least made of metal. I once saw a duct made of aluminum taped up w/duct tape, screwed to a plywood duct.
Douglas Hicks
General Fire Equipment Co of Eastern Oregon, Inc