11.   My only guess is it might have been a misguided vent pipe, going from, say, an upstairs bathroom, into the attic and into the flue.

12.   One more thing that might be easier than a separate vent pipe.

13.   Scrape away any old roofing cement under the shingles and around the vent pipe.

14.   Shuttle engineers believe the crack formed in a weld seam in the aluminum vent pipe due to contraction in the frigid vapors of the hydrogen.

15.   The exhaust gases escape through the same vent pipe used to supply air to the fire.

16.   The other thing a vent pipe does is take heat and moisture outside the house, and that is critical in hot months.

17.   The nozzle is simply a tube, and is unlikely to block the vent pipe.

18.   The smoke from the stick should be drawn up under the hood into the vent pipe.

19.   There are good gaskets that will prevent leaking around the vent pipe.

20.   They are normally placed against outside walls in any room of the house, and the vent pipe usually goes through the wall directly behind the unit.