A ventilation supply system shall deliver the required rate of supply air within an occupied space minimum of __________ above the floor.

A ventilation supply system shall deliver the required rate of supply air within an occupied space minimum of __________ above the floor.

• A. 1 inch
• B. 2 inches
• C. 3 inches
• D. 4 inches

Answer: (C)

The main concept here is proper air distribution height for a supply diffuser to ensure comfort and good mixing in the occupied space. Delivering the required supply air at a minimum height above the floor keeps the air from blowing directly at occupants’ feet and allows the jet to mix with room air as it travels. Three inches above the floor provides enough clearance for the air stream to enter the space and begin mixing without being blocked by floor-level obstacles or creating a strong draft along the floor. If it were as low as one or two inches, the air would be too close to the floor, increasing the chance of drafts at ankle level and poor mixing. Four inches is higher than necessary for most floor-level discharge systems and could reduce the effectiveness of the air distribution in achieving uniform comfort. So delivering the required supply air at a minimum of three inches above the floor best balances draft avoidance, mixing performance, and occupant comfort.

The main concept here is proper air distribution height for a supply diffuser to ensure comfort and good mixing in the occupied space. Delivering the required supply air at a minimum height above the floor keeps the air from blowing directly at occupants’ feet and allows the jet to mix with room air as it travels.

Three inches above the floor provides enough clearance for the air stream to enter the space and begin mixing without being blocked by floor-level obstacles or creating a strong draft along the floor. If it were as low as one or two inches, the air would be too close to the floor, increasing the chance of drafts at ankle level and poor mixing. Four inches is higher than necessary for most floor-level discharge systems and could reduce the effectiveness of the air distribution in achieving uniform comfort.

So delivering the required supply air at a minimum of three inches above the floor best balances draft avoidance, mixing performance, and occupant comfort.