To start, I'm not a first-timer.🙂 I have a 25 PDVC in my walk-out finished basement. It gets pretty cold in the winter. I usually run it 24/7 when it's cold out. I shut it down yesterday to do a deep cleaning. I had never pulled the combustion fan to clean it. The stove has a 3 foot horizontal exhaust with a 45. I put an OAK in last year. The fan blades had slight build up on them and there was quite a bit of ash built up behind the fan blade. I cleaned all the ash off the blades and behind the fan. I made a new gasket out of Lytherm sheet and put it back together. I had a tough time getting into the horizontal 3" flue. Everything is stuck together. The outer pipe actually came off the inner SS pipe and I pulled the whole outer pipe an 45 off. I was able to vac it out from outdoors. It was probably half full of ash. Shame on me. Once all cleaned out and reassembled, I started a fire in it. After 10 minutes I noticed a lot of smoke smell in the basement. It never cleared up. Not enough smoke to set of the smoke detector, but very noticeable. I shut it down and let it cool. Today I removed the outer flue pipe and elbow, plugged the 3" vent, plugged the OAK and lit 4 incense sticks (I use them to look for drafts) and closed the door. Let them fill the stove with dense smoke, pulled the plug out of the OAK and put a hair dryer in the OAK connection. Smoke was coming out of the combustion fan shaft are are pretty good. That makes sense because I wasn't getting noticeable smoke until after I cleaned it. I think the ash build-up was mostly plugging the area up. What type of seal are these combustion fans supposes to have? I ordered a new fan and full gasket set today. I'd like to see if I can fix the old one and use as a spare.