What is required for a natural draft venting system to operate effectively?

For a natural draft venting system to operate effectively, there must be a difference in density between the flue gas and ambient air. This density difference is primarily due to the fact that flue gases are typically warmer and thus less dense than the cooler ambient air. As the warmer flue gases rise, they create a natural draft that facilitates the movement of gases through the venting system. The natural buoyancy effect resulting from this density difference is what drives the upward flow of flue gases, allowing for efficient ventilation and preventing backdrafts.

While temperature does influence this process, it is the resulting density difference that is crucial for the natural draft mechanism to function. Other options like fan-powered systems and fuel supply are not characteristics of natural draft systems, making them irrelevant to the primary requirement for effective operation.