title_body: Home roasting and ventilation
upvoted_answer: I finally noticed that the chaff collection unit is actually several pieces that don't fit as well as they could.  I took it apart and sealed the seams with high temperature engine gasket sealant.  I then used the sealant to connect the vent hose to the top of the chaff collector (also a very rough fit). 
  
  I still have some problems with cold air inflow on the vent through the house wall, but I can disconnect the vent hose from the house vent and stuff it with rags or other temporary insulation material if I choose.
  
  All said and done the machine is leaking far less than half the smoke it was previously.  It seems the chaff collector was a main part of the problem.  This makes sense as the exhaust there is making a 90 degree turn, expanding into a chamber, then compressing back into another pathway.
  
  UPDATE:  
  
  Complete misunderstanding of the problem.  The exhaust vent is sized down and WILL connect and properly seal on a piece of exhaust pipe fitting.  I am not sure why the company sized it this way, but sealing the seams and using a piece of exhaust joint (rather than slipping the vent hose/pipe over the exhaust) works like it was probably designed to.