Last week the U.S. Center for Disease Control (CDC) update its website with additional information on how COVID-19 spreads between individuals, and in turn stressed the importance of transmission mitigation technologies, such as ventilation.

It was actually the second time the CDC asserted that the virus can be spread beyond 6 ft of distance in aerosol particles emitted by the human nose or mouth, after accidentally publishing a draft version last month. These particles can linger in internal environments for hours, and advises the following so HVAC systems minimize exposure and spread.

• Check to be sure your HVAC filter is correctly in place and consider upgrading the filter to the highest-rated filter that your system can accommodate (consult your HVAC manual or an HVAC professional for details).
• HVAC systems only filter the air when the fan is running, so run the system fan for longer times, or continuously. Many systems can be set to run the fan even when no heating or cooling is taking place.
• When used properly, air purifiers can help reduce airborne contaminants, including viruses, in a home or confined space.
• Improve ventilation with outside air to improve indoor air quality:
  • Open the windows, or screened doors, if possible.
  • Operate a window air conditioner that has an outdoor air intake or vent, with the vent open.
  • Open the outside air intake of the HVAC system, if yours has one (this is not common).
  • Operate a bathroom fan when the bathroom is in use or continuously, if possible.
  • Avoid these actions when outdoor air pollution is high or when it makes your home too cold, hot, or humid.
• Care should be taken with portable ventilation equipment, for example, fans, to minimize air blowing from one person directly at another person to reduce the potential spread of any airborne or aerosolized viruses.
• Running your HVAC system, using an air purifier or a portable air cleaner, and increasing ventilation are not enough to protect yourself and your family from COVID-19. Continue to follow other prevention guidelines.
• Use of ozone generators in occupied spaces is not recommended. When used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants.