Airflow Control Products and Plenums

HVAC ductwork design is incorporating more specialized airflow supply, return, filtration, re-circulation and disinfection equipment as requirements for indoor air quality and safe building are changing with standards that have been reevaluated and adapted to accommodate the evolution of environmental and social conditions.

Plenums are an important component in HVAC/R system design, sometimes referred to as an air box or a plenum box, they help to protect supply air and equipment, act as a reservoir for the volume of intake equipment air, and, depending on the interior design and position of the component, may also serve to direct airflow back into the returned air supply using diverter structures.

A pyramid diverter, fabricated by our team for a client, is pictured here:

The concave point on the back wall of the plenum serves as a dispersion point for air that reaches this termination point in the HVAC system. A blunt force of airflow against a flat surface would cause inefficient aerodynamic return force, as competing vectors would lose energy colliding into side walls and not reaching the optimal flow point.

The pyramid diverter, and other internal ductwork airflow controls, such as the vanes in the nested 90 degree tee shown below serve to channel the force of airflow impact by varying the impact surface to a degree that directs the air to the required equipment intake, which may be a fan, air conditioning unit, supply or return duct.

In large-scale project plans, a plenum may be designed with more than one opening with different flow directions, insulated, tie-rod reinforced, or be used for physical access into the ductwork system, either by person or machine, sometimes a combination of the two such as a drone and controller, such as the access unit shown below fabricated by our team for our customer’s installation at the University of Virginia.

Additionally, plenum boxes may also be fit with specialized equipment designed to detect fire and close off the compromised section of the HVAC/R system to air supply, contributing to more efficient, life-saving fire suppression.

Contact our construction consulting team to find out more about how our fabrication capabilities can optimize the specialized airflow control components of your mechanical installation, while keeping your budget and schedule on track.

Our Airlow Control Products Include:

Equipment Plenums



Access Plenums


Custom Construction



Custom 90-Degree Off-set Elbows


Insulated and Reinforced Vaned Elbows


Fire Suppression


“Ten years ago Professional Mechanical was at a crossroad. We had the capability of handling larger projects, with the exception of our shop fabrication, being manual, keeping up with the ever increasing speed of project schedules. Since then our continuing relationship with Phoenix Metals enables us to consider all types and sizes of projects. Their knowledge of SMACNA requirements and unwavering desire to service their customers sets them apart from all other fabrication shops.”

David C. Humm, Professional Mechanical Contractors, Inc.

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