What type of venting system utilizes mechanical means to remove flue or vent gases?

The correct choice is the Mechanical Draft System, which is specifically designed to use mechanical means, such as fans or blowers, to remove flue or vent gases. This type of venting system is commonly found in applications where natural draft systems may not be sufficient, such as in larger appliances or those located in areas where the natural gas flow is hindered.

In a Mechanical Draft System, the mechanical components actively assist in the removal of exhaust gases, providing better control over the venting process and improving efficiency and safety. This system is particularly important in buildings with tight construction where the natural draft might not function properly.

On the other hand, Natural Draft Systems rely on temperature differences and buoyancy to drive the flow of gases, without mechanical aids. Gravity Draft Systems operate under similar principles of buoyancy based on gravitational forces. Hybrid Draft Systems combine elements of both natural and mechanical draft but are not solely reliant on mechanical means for venting. Thus, while the other options provide various venting solutions, they do not utilize mechanical assistance to the extent that a Mechanical Draft System does.