Mitigating airborne infection risk is now a critical step every school, business, company, and institution must take. As the coronavirus (COVID-19) pandemic progresses with new variants, aerosol transmission remains a significant concern. In response, ASHRAE and the CDC have issued recommendations to facility managers on reducing airborne SARS-CoV-2 viral particles within indoor spaces.
These guidelines are built upon crucial indoor air quality improvements that when combined with PPE, vaccination, and disinfection protocols, can significantly reduce COVID-19 transmission risk. Read on to see our overview of these recommendations and how indoor air quality improvements can even reduce the spread of the Omicron variant.
In reference to the CDC's guidelines to control the COVID-19 virus, ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning Engineers) redeveloped their recommendations for ventilation system design and operational facility standards.
ASHRAE constructed an epidemic task force to study the pandemic and issue their findings for public use as part of these new recommendations. ASHRAE's task force discovered a significant correlation between increasing ventilation rates and the subsequent decrease in airborne pathogen infection risks.
In response to these findings, ASHRAE issued new technical guidance to mitigate the spread of COVID-19 through respective indoor air quality (IAQ) improvements. CDC public health officials in coordination with ASHRAE re-published these findings to support their growing COVID-19 prevention protocols and guidelines.
ASHRAE's core recommendations are essential guidance from minimizing classroom-based COVID-19 transmission to reducing pathogen spread in workplace settings. See below the five steps ASHRAE recommends businesses and schools to take to protect their community from airborne pathogens.
The first priority is to follow the most recent regulatory and public health guidelines in your area. As COVID-19 continues to evolve with the Omicron and Delta variants, these guidelines may continue to change rapidly when positive cases surge. However, remaining aware and attentive to these changes will ensure the best chance of reducing COVID-19 transmission risk. Current public health guidance includes using PPE and N95 masks alongside social distancing and maintaining building cleanliness.
ASHRAE also recommends the implementation of hand hygiene stations (hand sanitizer) and altering occupant schedules to reduce density and broad peer-to-peer contact. Additionally, some governmental bodies such as OSHA may soon issue vaccination mandates for businesses within particular employment and industry criteria. Be sure your organization is prepared to handle any potential new guidelines.
The second essential step ASHRAE recommends to reduce airborne SARS-CoV-2 (the virus that causes COVID-19) transmission is through improving indoor air quality (IAQ). According to ASHRAE, a critical part of IAQ improvements is leveraging HVAC systems to enhance whole-building ventilation and filtration. ASHRAE's research indicates that upgrading HVAC filters to a MERV 13 filter will help provide HEPA-like filtration reducing the presence of airborne pathogen particulate.
ASHRAE's guidance suggests that MERV 13, alongside 24/7 operation of HVAC systems, will dramatically improve IAQ within facilities. When combined with additional air cleaning and air purification devices, the presence of airborne SARS-CoV-2 particles can be significantly reduced. ASHRAE also strongly recommends using portable room air purifiers that feature True HEPA filters.
These mechanical air filtration systems provide localized hourly air exchanges and can capture airborne particles as small as 0.3 microns in size. ASHRAE also recommends Upper-Room Ultraviolet Germicidal Irradiation (UVGI) Systems to provide additional air cleaning. The design of Upper-Room UVGI systems and their use of UV-C disinfection enable them to rapidly inactivate pathogens (including SARS-CoV-2) present within indoor air.
Whole-building air distribution is a critical component of maintaining indoor air quality. Therefore, ASHRAE recommends that a building's air distribution be strictly monitored and remain operationally uninterrupted. For air distribution through ductwork and HVAC systems, ASHRAE suggests facility managers control and monitor airflow for individual zones and rooms.
When viral transmission risk assessments are completed, facility managers can determine the introduction of clean versus the recirculation of potentially contaminated air. ASHRAE states, operators should be cautious not to cause strong recirculation air currents to prevent the increase of direct viral transmission from occupant to occupant.
Facility managers should also consider alternative measures to increase building air distribution that can reduce airborne pathogens. ASHRAE recommends using portable air purifiers to increase the clean air delivery rate (CADR) or air exchanges per hour (ACH) within high-occupancy spaces. Depending on room size or occupancy density, make sure the air purifier designated for the space can support between 3-4 air exchanges per hour.
In order to keep continuous whole-building air distribution, ASHRAE recommends facilities managers also monitor HVAC operation and system maintenance. The top priority for monitoring is to ensure the system is supplying an equivalent clean air supply. ASHRAE suggests keeping the clean air intake frequently open and prioritizing air supply to higher occupancy spaces. When necessary, ASHRAE recommends fully exchanging the air within high-risk spaces to reduce airborne transmission. This guidance also applies to ensure spent, and contaminated air is exhausted from the system is not re-introduced to the building's airflow.
ASHRAE recommends performing system commissioning to keep all aspects of building ventilation and HVAC systems in working order to reduce airborne COVID-19 transmission. The primary goal of HVAC system commissioning is to check if the systems are operating in the initially intended manner. According to ASHRAE, the commissioning process is a thorough way of "verifying that a facility and its systems meet the Owner's Project Requirements (OPR)." In the commission process, all equipment and material used in the HVAC system will be checked for proper installation and function.
The same HVAC equipment will also be tested, adjusted, and balanced (also known as TAB). It is critical to perform HVAC system commissioning, especially after conducting upgrades to the system such as installing new ductwork, in-duct air purifiers (UVGI, hydroxyl generators, or bi-polar ionization), or replacing central equipment. These changes could impact the system's original function or impede building air distribution.
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