HVAC and Healthy Stores: What May, or May Not Work

With the onset of COVID-19, some Hixson clients have asked whether it is possible to upgrade their HVAC systems to include High Efficiency Particulate Air (HEPA) filters in an effort to clean the air in their stores and protect their staff and customers.

Per the Environmental Protection Agency, HEPA filters “can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm).”  (Current research suggests that this size would include aerosol COVID-19 particles that could enter the filtration system.)

That’s good, right?

The short answer is: It’s complicated. Unfortunately, most retail stores use packaged rooftop mounted HVAC equipment, commonly referred to as Roof Top Units (RTUs), which cannot create the type of static pressure necessary for HEPA filters to work properly.  Retrofitting RTUs so that HEPA filters will work will require an enormous amount of capital (and time) to either retrofit existing equipment, or to install downstream filters and fans.  Either of these efforts will require greater horsepower from the RTU in order to push air through the HEPA filter – and most package RTUs are not designed to add horsepower, which requires a duct-mounted booster fan.



What else can a store owner do?

One option for some stores, under the right conditions, is the addition of portable, local, freestanding air purifiers with HEPA filter. Another possible option Hixson is currently examining is to add Ultraviolet Germicidal Irradiation (UVGI) to enhance the filter system.  Again, it’s complicated: The use of UVGI in HVAC to combat COVID-19 will require a number of factors to be considered, including:

  • What spectrums are most effective (UVC – with wavelengths between 200 – 280 nanometers (nm) is currently recommended)?
  • How will they be implemented within the total HVAC system (typically mounted in the RTU)?
  • How many lights are required?
  • What is the necessary air velocity as it passes through the UVGI exposure area?

What’s our take-away?

No magic HVAC bullet exists.  Whether HEPA filters, UV lights, or something else, store owners still will not completely eliminate the threat of COVID-19 from air circulation. The threat of contaminated air coming through exterior doors and openings and from occupants of the space will still exist. However, these HVAC options offer intriguing possibilities and merit further investigation.

If you want to discuss your own store’s HVAC system capabilities and possible options, contact Hixson.


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