What is a Tri-Stack® Fume Exhaust System?

Mixed Flow Fan Operation Diagram

  1. Wind band entrains outside air above fan motor to enhance discharge volume and effective stack height
  2. Up to 170% of free outside air introduced into the airstream prevents odor and re-entrainment
  3. Special materials and coatings are available for severe environment duty
  4. Specially designed, mixed flow impellers provide high pressure and volume, with no stall region, and at low RPM. The impeller mounts directly to the motor shaft without belts or pulleys
  5. Direct drive motors are virtually maintenance-free with typical bearing lifetimes of L-10 100,000 hours
  6. Modular construction speeds and simplifies installation, reduces costs and downtime
  7. Extremely low vibration levels eliminate the need for spring isolation and flex connections


Tri-Stack® systems operate on a unique principle of internal and external exhaust stream dilution. They entrain outside air (up to 170% by volume) with the primary exhaust stream to produce a substantially diluted exhaust stream. A unique exhaust nozzle design enhances flow and pressure to increase stack outlet velocities while minimizing horsepower requirements. The resultant discharge plume (up to 350’ high) produces an effective stack height sufficient to penetrate the building boundary layer and safely disperse exhaust into the free air stream. Once there, it cannot be re-entrained into building inlets or adjacent buildings.

Because Tri-Stack® mixed flow fans introduce up to an additional 160% of free outside air under their wind-bands and through their motor chamber areas, a substantially greater airflow is possible for a given amount of exhaust without additional horsepower. Outstanding dilution performance effective eliminates pollution and odor problems with extremely high efficiency.

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Tri-Stack® Fan Selection Program