Residential HVAC Installation Practice Exam

A ceiling plenum is not a type of duct system. A plenum is a central distribution box for HVAC systems that connects to various ducts to distribute air throughout a building. The reducing plenum is designed to decrease the size of the ductwork gradually for efficient airflow, while the return plenum connects the return ductwork to the HVAC system. However, a ceiling plenum typically refers to the space between a drop ceiling and the structural ceiling and is not a type of duct system.