A draft hood used to effectively ventilate the area around older “gravity vent” furnaces. Because current furnaces lack this feature, the condition described below results in some unburned gas remaining in or around the furnace in the off cycle. HVAC distributor cfm Distributors shared how to explain this to a homeowner.
When a gas furnace shuts off, at least half of the residual gas in the manifold will dissipate in the air immediately around the orifices. It may drift outside the furnace and be noticed by a homeowner, resulting in the belief that there is a leak in the gas delivery system or furnace components. Even though it is too diluted to burn, it is detectable with an electronic gas leak detector.