What percentage of the entire volume served by the system must be supplied for return air from a room?

• A. 20%
• B. 25%
• C. 30%
• D. 35%

Answer: (B)

The requirement that 25% of the entire volume served by the system must be supplied for return air from a room is grounded in HVAC (Heating, Ventilation, and Air Conditioning) practices. This percentage ensures that there is an adequate balance between the air being supplied to a space and the air that is being returned.

Maintaining this balance is crucial for effective air circulation and maintaining good air quality. By returning 25% of the air from the room, the system can effectively mix the air, ensuring that stale air is replaced and fresh air is circulated, which contributes to a consistent and comfortable environment.

This standard is based on various considerations, including the system’s ability to handle variations in occupancy and usage of the space, the efficiency of air filtration, and the overall comfort of the occupants. By adhering to this guideline, HVAC systems can achieve better performance and energy efficiency, enhancing both occupant comfort and system longevity.