I've got a vintage natural gas furnace in my basement, works fine, but can anyone tell me what this Chromalox vent thingie on my upper level ceiling is for, and what the heck its purpose is? Obviously it goes to the roof, but it does not emit any air or sound on the interior of the house. It has a large slim wheel type dial labeled "Low" on one end and "Warmer" on the other, which will click a few times the more you thumb it in one direction. Thanks much!!!