A filter’s ability to capture and hold airborne particles is expressed by its MERV, or Minimum Efficiency Reporting Value. MERV ranges from 1 to 16; the higher the number, the better the filtering. ASHRAE reports that filters with a MERV of 13 or higher are efficient at capturing airborne viruses, and that a MERV of 14 or above is preferred. HEPA (high-efficiency particulate air) filters remove at least 99.97% of airborne particulates, providing even better efficiency than a MERV 16 filter. Upgrading the MERV of your air filters may be a relatively inexpensive solution if you are already using a fairly efficient filter. However, it is important to consult a professional before making these changes. Increased air pressure from the higher-MERV filters can have a detrimental effect on your system if it is not sufficient to handle these filters.

Although all ultraviolet (UV) light can kill or deactivate pathogens, the UV-C wavelength is the most effective. These specialized lights can be placed within or outside of HVAC ductwork to inactivate viruses, bacteria, mold and fungi. In general, the UV-C wavelength is safe for humans, although protection from exposure—especially for the eyes—is necessary.  Since UV-C does not physically remove the neutralized pathogens from the air, it must be used in conjunction with a proper filtration system.

Mixing a higher than normal amount of conditioned outdoor air into recirculated air can improve indoor air quality under certain circumstances. The most common ways to achieve high ventilation are to use an air economizer within the existing HVAC system and/or to add a dedicated outdoor air unit, also known as a make-up air unit. Important considerations in this strategy include the level of allergens and pollutants in the outside air, as well as extremes of temperature and humidity in the area where your building is located.

With this technology, an electronic device creates charged atoms from oxygen molecules. These atoms attach to airborne particulates—such as mold, bacteria, allergens and viruses—deactivate them and make them large enough to be trapped by filters. Air ionization may reduce the need for outdoor air in the overall system, although a trained professional is required to make this determination.

Maintaining optimal temperature and humidity in a conditioned space can often help to minimize growth and spread of airborne pathogens and other contaminants. In fact, according to the American Society for Microbiology, an indoor relative humidity between 40% and 60% may help to limit the spread and survival of the virus that causes COVID-19. Using a humidifier within the HVAC system and/or dehumidifying the air with a re-heat process or other technique can help to achieve and maintain the proper humidity.