by Larry Rockefeller, CIH, CSP
Director, Industrial Hygiene Services

As we move through this global pandemic, many of the buildings that we routinely entered pre-pandemic are now partially occupied or remain vacant.  Buildings such as schools, churches, restaurants, and commercial office spaces have been significantly impacted by state and local restrictions aimed at mitigating COVID-19 transmission.

Since the start of the pandemic, the Center for Disease Control and Prevention (CDC) has been a leading agency that has consistently provided guidance to protect the public. While physical separation is recognized as the most effective method for infection prevention, the CDC and others realize that this is not realistic or feasible for many businesses. In response, the CDC published guidelines for use when re-occupancy could not be avoided. These guidelines promoted social distancing, but also highlighted cleaning and disinfecting common contact surfaces as the primary method of reducing COVID-19 transmission.1

As the pandemic continued through 2020, it became apparent through research and published studies that airborne transmission was a significant contributing factor to the escalating case count and protracted pandemic. This created a large shift in published guidance. While the CDC has prioritized cleaning and disinfection of surfaces/objects (fomites), the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) took the lead providing guidance on reducing airborne COVID-19 transmissions within indoor environments.  ASHRAE assembled a task force that issued a COVID-19 Building Readiness Guide.2 Since its original publication last year, the guide has been updated in conjunction with our understanding of the COVID-19 virus.  The current guide recommends utilizing a team approach to develop and implement readiness plans to best prepare for building re-occupancy. 

Critical aspects of the Building Readiness Guide include a combination of non-HVAC related strategies with specific HVAC-related strategies including increasing ventilation, improving air filtration, and using air cleaning devices.  Enhanced ventilation can be accomplished by increasing the amount of fresh air (dilution ventilation), increasing total supply and air changes per hour, and flushing the building with fresh air before and after occupancy. Air filtration can be improved by upgrading standard HVAC filters to MERV 13 or better. If the HVAC system’s capabilities will not allow for this degree of filtration, the highest efficiency filter should be used based on the HVAC’s system capabilities. When installing filters, it is important to assure each filter is properly seated in the filter rack to avoid filter by-pass.  Standalone air cleaning devices are also an appropriate solution if a higher MERV filter cannot be installed or if there is a need for supplemental air filtration.  New air cleaning technologies such as ultraviolet light (UVC) and bipolar ionization have been marketed to reduce or eradicate airborne COVID-19.  ASHRAE has provided guidance on technologies,3 summarizing each type of product and listing how they perform and if they are effective.  In addition to HVAC-related strategies, the readiness guide provides recommendation for alternative approaches to control COVID-19 transmissions including controlling building occupancy, mandatory use of face coverings, social distancing, personal hygiene, and cleaning requirements.

The CDC4 and ASHRAE have issued guidance on re-occupancy of buildings related to extended shutdown or reduced operations.  These guidelines address hazards such as mold, lead and copper contamination, as well as Legionella bacteria.  Mold growth could result from water intrusions from pipe or roof leaks that go unnoticed due to reduced building occupancy.  Mold growth can also form in buildings that have improper indoor air conditions that may result from poorly maintained or malfunctioning HVAC operations. Lead and copper contamination occurs in domestic water supply lines that are left stagnant allowing the pipe to corrode and metals to leach into the water system. Legionella bacteria growth follows the same principal as lead and copper contamination, where stagnant water creates an excellent environment for bacteria to proliferate.  The CDC guidance provides cleaning procedures and other recommendations to address these hazards.

The recognition and understanding of airborne transmission has driven changes to re-occupancy guidance provided by the CDC and scientific community. As strides continue to be made toward ending the pandemic, the reality of complete re-opening of schools, universities and workplaces continues to grow. If appropriate action is taken to prepare for building re-occupancy, the building owner, property manager, and occupants should be confident in the returning to a safe and healthy workplace.

Is your building prepared for post COVID re-occupancy? Learn more about how The EI Group, Inc. can help with reducing airborne transmission in your workplace. Contact EI’s Director of Industrial Hygiene Services, Larry Rockefeller, CIH, CSP, today at (919) 459-5257or [email protected].

  1. “Guidance for Cleaning and Disinfecting: Public Spaces, Workplaces, Businesses, Schools, and Home” Centers for Disease Control and Prevention, April 28, 2020
  2. ASHRAE Epidemic Task Force, Building Readiness, Updated 2-1-2021
  4. Guidance for Re-Opening Buildings After Prolonged Shutdown or Reduced Operation, CDC, 9-22-20