Clean Air Action

by Katie Lee

— By Doug Engel —

Protecting guests from COVID-19 in restaurants and retail stores without breaking the bank.


Restaurants and retail stores have been hit hard by plummeting business and consumers shifting to buy goods online. Ensuring safe physical spaces for dining and shopping is not just important, it’s essential to the recovery of these important sectors of the economy. What’s the best way to protect the health of customers and staff while being sensitive to the current financial challenges in these industries?

Doug Engel, enVerid Systems

Like the changing guidance associated with COVID-19 itself, research and analysis has led to an evolution in recommendations for virus mitigation in facilities. While initially the emphasis was on maximizing outside air ventilation, experts have since pointed out the HVAC system challenges and the high-energy penalty associated with that strategy. The cost of increasing outdoor air substantially threatens to exacerbate the financial injury already suffered by the nation’s restaurants and retail stores. ASHRAE recently updated its Commercial Guide acknowledging these issues and recommending the following strategies:

  • If there are significant energy impacts from increasing outside air for ventilation, use minimum outside air as required by ASHRAE Standard 62.1 with a minimum MERV-13 filter.
  • If outdoor air quality is not healthy per Section 4 of ANSI/ASHRAE Standards 62.1-2019, especially high particulate matters, do not open windows or increase ventilation without using the proper filters.
  • Maintain relative humidity between 40% and 60% where possible.
  • Consider portable air cleaners when a room has insufficient outside air per code requirements and filtration is below MERV-13.
  • Consider UV-C light as an enhancement where spaces require additional measures, e.g. spaces that serve vulnerable occupants, or when MERV-13 filtration or 100% outside air are not possible, etc.

When outside air must be conditioned to achieve a comfortable temperature and humidity, energy is being expended. In fact, conditioning of outside air is the largest cost of operating a commercial HVAC system.  The more conditioning that must be done to bring outdoor air to a comfortable temperature and humidity level, the more energy is used, which is a costly strategy.

After all, leaving windows and doors open and cranking up the outside air in these facilities isn’t a practical answer most of the time. The number of 65- to 75-degree days with humidity around 50% and no precipitation varies widely across the country and over the year, but it’s safe to say that it’s not the majority of days or nights in most of the U.S. In some locations, such as California during the current wildfire season and locations near major roadways or industrial sites, outdoor air quality is poor. Beyond the negative impact to customer and staff experience, exposure to particulate matter from dirty outdoor air and humidity levels outside of the recommended 40-60% range have been found to increase the virulence of COVID-19 infections, actually facilitating the spread of the virus and making symptoms worse.

Improved filtration is an important solution to the challenge of protecting air quality, but it’s not always easy. In some cases, an existing HVAC system cannot handle a straight swap to a higher efficiency filter. Systems are designed to move air at a specific range of velocities, and HEPA and similar filters require higher velocities to move air through them. Installing a filter that the HVAC system can’t handle might come close to blocking it entirely, leading to less air moving through the system, the exact opposite of what a facility manager would hope to achieve.

In cases where relying on more outdoor air isn’t viable and replacing the HVAC system or increasing the filtration is not a possibility, supplemental local filtration can be an affordable answer.

Adding ceiling-mounted units that operate independently of the HVAC system with high-efficiency filters can provide peace of mind without breaking the bank or stressing the system. And because they’re off the floor and out of the way, they aren’t a distraction with cords across the floor and fan noise. Also, they can’t be easily moved or unplugged like portable units can. These units sometimes even include UV lights that kill any viral particles that might be caught on the filters so that they can be safely removed for filter replacement at any time.

Many experts now recommend an “all of the above” approach to indoor viral remediation. With supplemental air purifiers, you can add enhanced filtration to whatever added ventilation is practical to create many more air changes in your facility per hour. In choosing air purifiers, keep these pointers in mind.

  • Look for independent testing that has verified that purifiers work as they claim.
  • Look for ceiling-mounted units to prevent tripping hazards or unplugging and moving units in a busy store or restaurant.
  • Make sure that you’re getting a sturdy and durable commercial- or industrial-grade unit, not a residential machine.
  • Pay attention to the number of air changes per hour the units will deliver, and make sure that together with your existing HVAC system, they will bring your facility to the recommended five air changes per hour to keep the viral load low. You may need more than one unit to adequately treat the space.
  • Consider units that include UV-C lights inside, not to clean the air (a controversial claim because of the speed at which the air moves through the unit vs. the longer time needed for UV light to sterilize the air) but instead to continuously clean the filters.
  • Be sure that ceiling-mount purifiers have wall-mounted control panels. You don’t want to have to send someone up a ladder to monitor the status of the purifier.
  • Consider the reassurance that seeing an air filter installed below the ceiling might provide to your customers. Although just as effective when installed in the plenum, a visible air purifier may offer peace of mind. Just make sure that it is installed at the proper height (too high or too low will not be effective on the air your customers are actually breathing).

Protecting customers and staff from COVID-19 infection is a critically important undertaking, as is preserving the restaurant and retail industries. The only way to achieve both goals is to use smart strategies to clean the air in restaurants and stores efficiently and affordably. While outside air is often the first recommendation for COVID-19 mitigation in indoor commercial spaces, it is essential to find and prioritize more affordable and equally effective alternatives. Higher-efficiency, local air filtration is a smart, effective strategy.



— Doug Engel is senior vice president, sales & marketing, for enVerid Systems, a Boston-area provider of commercial indoor air quality products including localized high filtration devices and the award-winning HVAC Load Reduction® (HLR®) module.





You may also like