Plenum is defined as a compartment or chamber to which one or more air ducts are connected and that forms part of the air-distribution system.

• A. Plenum
• B. Occupancy
• C. Health Care Occupancy
• D. Mixed Occupancy

Answer: (A)

A plenum is a compartment or chamber that connects to air ducts and forms part of the air-distribution system. This definition describes the space that channels and houses air as it moves through the building, such as the area above a drop ceiling or a dedicated air-handling space that ducts feed into. In NFPA 101 terms, this space is considered part of the air-distribution system because it directly facilitates the movement of air for ventilation and pressure control.

The other options refer to how the space is used or who occupies it—occupancy, health care occupancy, mixed occupancy—rather than to the air-handling space itself. They don’t define the actual channel through which air is distributed, so they don’t fit the given definition.