What defines a natural draft venting system?

A natural draft venting system is defined by its reliance on natural atmospheric pressure to facilitate the flow of exhaust gases away from a gas appliance. This option accurately describes how the system operates; it relies on the density differences between hot gases produced during combustion and the cooler outside air to create a draft without using any mechanical devices.

In a natural draft system, the exhaust gases rise due to their lower density and are expelled from the vent, which is typically installed vertically. This process occurs under non-positive static pressure, meaning that there isn't any additional pressure forcing the gases out; instead, the natural buoyancy of the warm gases is what drives the venting action.

It's important to note that other systems, such as forced draft or power vent systems, utilize fans or blowers to actively remove combustion gases, which is not the case for a natural draft system. This distinction is crucial for understanding how different venting systems operate and their applications.