What should be the condition of a flue pipe in relation to the outlet of a furnace?

The correct choice emphasizes the important principle of maintaining consistent flue pipe size in relation to the furnace outlet. The flue pipe should be at least the same diameter as the furnace outlet to ensure proper venting of combustion gases. This consistency helps maintain optimal airflow and minimizes the risk of backdrafts or insufficient venting, which can lead to the accumulation of harmful gases within the living space.

Having a flue pipe that is the same diameter as the outlet ensures that the gases expelled by the furnace can move freely and efficiently, allowing for effective ventilation. A reduction in size could restrict the flow of gases, increasing the likelihood of blockages or pressure changes that can compromise safety.

In general construction practices, adhering to the manufacturer's specifications for flue sizing is critical. This consistency not only promotes safety but also enhances the efficiency of the heating system. It is essential for home inspectors to recognize these guidelines to ensure that heating systems operate effectively and safely.