Economizer Mixing Box

Taking outdoor air into the building to help cool a space and provide required ventilation is a well-known technique; to do it to maximum effect takes careful analysis and proper selection of components and control strategies. A mixing box carries out the economizer function of providing cooling assist and ventilation in buildings by taking in outdoor air in a single, packaged device.
Read our article published in the ASHRAE Journal titled "How Effective are Mixing Boxes at performing the economizer function?" on the effectiveness of using a mixing box for air mixing and strategies for improving its effectiveness.
Mixing boxes without baffles or static mixing devices, like those available in the Plenums Filter Rail Mixing Boxes, can only be recommended for meeting the ventilation requirement of ASHRAE Standard 62.1-2019 and not the energy-efficiency requirements of ASHRAE Standard 90.1-2019. Use the Plenums Filter Rail Mixing Boxes to provide additional air filtration and promote better mixing for a more efficient economizer installation. Contact us to discuss your requirements.


  • Galvanized steel construction.
  • Fully insulated.
  • Parallel blade dampers with bronze bushings.
  • Damper linkage and hardware.


  • Economizer control.
  • Low leak dampers.
  • Filter rack.
  • Vertical application.
  • Custom designed arrangements.
  • Built in relief damper.
economizer mixing box

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