Uploaded May 2011 | Updated September 2026, 15 hours ago

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Our heating and air conditioning instructor at my community college built this mock up with an old furnace to show us what happens when combustion air supply and exhaust is disrupted or interfered with due to improper installation or maintenance. The door to this "furnace closet" is clear plastic so one could see what happens to the flames under such conditions.

Demonstrations include leaving the blower door off, blocking off the fresh air intake vents, and covering the chimney.