HVAC Journeyman Practice Exam 2026 - Free HVAC Practice Questions and Study Guide

The primary role of a furnace plenum in an HVAC system is to distribute heated air throughout the space being conditioned. The plenum serves as a central distribution point where heated air from the furnace is channeled into various ducts that direct the airflow to different rooms or areas within a building. By effectively managing and directing this airflow, the plenum helps to maintain consistent temperatures and ensure that the heating system operates efficiently.

While filtering air, collecting return air, and managing humidity levels are important functions in an HVAC system, they are not the main purpose of a plenum. Air filtration typically occurs in air handlers or filters themselves, and return air is usually managed through separate ductwork that channels air back to the furnace or air conditioning unit. Humidity management is often handled by dedicated humidifiers or dehumidifiers within the HVAC system. Thus, the correct answer centers on the plenum's vital function of air distribution within the system.