AHU mixing dampers are used to?

• A. Use outside air for cooling to reduce energy use and supply fresh air into the building
• B. Block outside air to prevent drafts
• C. Mix only recirculated air with exhaust air
• D. Control humidity levels in outside air

Answer: (A)

Mixing dampers in an air handling unit blend outdoor air with return air to create a controlled mixed airstream. This lets the system bring in fresh outdoor air for ventilation while taking advantage of favorable outdoor conditions to reduce cooling energy use, often enabling economizer operation. The result is a balanced supply air that helps both energy efficiency and indoor air quality.

So, the purpose is to use outside air for cooling to lower energy consumption and provide fresh air to the building. It isn’t about blocking outside air, mixing only with exhaust air, or directly controlling humidity—the damper mainly modulates the mix of outdoor and return air.