Mixing Box is used for mixing air in HVAC systems. This air-mixing plenum provides a supply air mixture for onward distribution to the building or premise having the ventilation system. Air is mixed to save energy and improve energy efficiency. Air not mixed is rejected to the atmosphere as exhaust air. We provide Mixing Box HVAC for the HVAC systems. It is used to mix the return air flow with the outside air flow. The box consists of three sets of dampers to control the fraction of the outside air in the supply air while maintaining the supply airflow rate approximately constant.