A(n) _____ draft is when the furnace has a fan that sucks air into the combustion chamber, through the heat exchanger, and blows out through the venting system.

An induced draft refers to a system where a fan, specifically designed for this purpose, actively pulls air into the combustion chamber of a furnace. This fan creates a negative pressure that helps to increase efficiency by ensuring that the necessary air is drawn through the heat exchanger and then expelled through the venting system.

The induced draft is crucial because it allows for better control over the combustion process, which often results in improved efficiency and reduced emissions. This method is particularly beneficial in situations where natural drafts may not provide adequate airflow due to design or environmental issues. In contrast, natural draft systems rely on the natural buoyancy of hot gases to rise and create airflow, which can be less reliable in certain conditions.

This function of an induced draft system is essential for modern furnaces, as it enhances overall performance and safety by ensuring a consistent flow of air necessary for proper combustion.