What is the defining feature of a power venting system?

The defining feature of a power venting system is that it uses a fan or mechanical means to remove flue gases. This characteristic distinguishes power venting from other systems that rely on natural draft or convection to expel exhaust. In a power venting system, the fan actively pushes the gases out of the appliance and into the venting system, allowing for more flexibility in installation and performance, especially in situations where natural draft may not be sufficient due to the design of the building or the location of the appliance. This capability is particularly beneficial in tight spaces or when venting vertically is not feasible.

Natural draft systems are reliant on the buoyancy of hot gases to rise and exit, which can lead to inefficiencies or backdrafting in certain conditions. Power venting systems mitigate these concerns by mechanically facilitating the removal of combustion byproducts, ensuring safe and efficient operation. This makes option B the most accurate description of a power venting system's functionality.