The onset of the COVID-19 pandemic had people sharing an array of strategies for disinfection and disease prevention. The ensuing months showed that the SARS-CoV-2 virus is primarily spread through the air via contaminated droplets, prompting a new wave of air purifying technology. A feature article in Chemical & Engineering News, the weekly newsmagazine of the American Chemical Society, details the various air purifier technologies and their efficacy against the coronavirus.
Although official guidance from the U.S. Centers for Disease Control and Prevention (CDC) suggests that social distancing and mask wearing are the most effective ways to prevent the spread of COVID-19 indoors, they also state that air purifiers can help reduce airborne contaminants, including viruses. These gadgets rely on various technologies, writes special correspondent Mark Peplow, and whereas some are proven to work, others require more data. Filtration with high-efficiency particulate air (HEPA) filters made from glass or polymer fibers is the most popular choice in hospitals and other clinical settings.
Another air purification method involves using ultraviolet C (UVC) light to deactivate viruses, including SARS-CoV-2, by making them unable to replicate. However, direct exposure to UVC can be harmful to people, which has led experts to suggest placing the lights in HVAC ducts, or lowering the intensity of the UVC light so that it can’t penetrate living cells but can still kill airborne viruses. Another type of purification is known as bipolar ionization, which uses high voltage electrodes to create positive and negative ions from the air that can then attach to viral particles and prevent them from spreading. Although makers of ionization purifiers tout their ability to combat SARS-CoV-2, experts argue that the research has not been as convincing as that of other methods. Scientists agree that even with air purifiers, masks and social distancing should still be the first line of defense against the spread of SARS-CoV-2.
Cities and states across the nation are lifting safer-at-home orders, and businesses are taking extra precautions to prepare for the return of customers but cleaning high-contact surfaces and maintaining safe social distance is only the start. Findings by Richard Shaughnessy, director of The University of Tulsa’s Indoor Air Program, show that improving air quality through enhanced ventilation and filtration can decrease the advancement of harmful bacteria and viruses, like COVID-19. “We’re trying to get simple, useful, practical information to the public that they can use now,” he said.
Clean air is key
According to Shaughnessy, the virus can be transmitted through both human contact and aerosol transmission. “This virus can survive on smaller aerosols (less than 5 microns in size) in the air for three to four hours, and on surfaces, depending upon the surface, for two to three days,” Shaughnessy explained. “If ever there was a time in history for improved indoor air quality, it would be now,” Shaughnessy stated.
After being confined at home for weeks, residents are ready to shop, visit salons, see movies and eat at local restaurants. “There is an immediate need to identify what businesses can do to supplement social distancing measures, such as improving indoor air quality,” Shaughnessy explained. “These practices go hand-in-hand with other effective approaches such as the cleaning/disinfecting of high-contact surfaces.”
When fighting viruses and bacteria, few businesses consider cleaning the air in their buildings, adding supplemental filtration or upgrading the filtration system they already have established. “All air cleaning requires is making sure that your filters are in place,” Shaughnessy said. “If you have a heating or cooling system, make sure your filters are adequate. Use the highest efficiency filters you can, but remember you only have fresh air filtering through the mechanical system when the system is running.”
For more than 25 years, Shaughnessy’s research has focused on indoor environmental concerns. In the past decade, he has specifically investigated whether illnesses are more easily transmitted because of inadequate ventilation or air filtration. Shaughnessy and his team have conducted testing in commercial businesses, homes and densely occupied environments such as schools and hospitals.
Constant ventilation to remove human aerosols
“If you’re relying on your heating and cooling system, you turn it on, and it moderates as a function of temperature. You want to put that fan on, so it runs 24/7. Otherwise, the system may run only 18% of the day and you’re getting little filtration during that time,” he said.
The virus also can be harbored on particles that fall out of the air onto floor surfaces, and Shaughnessy explained that if someone is shedding the virus, tens of thousands of particles from skin can dissipate to the floor. As people step across the floor, the particles are resuspended back into the air where they may be breathed in.
“People do not have to buy gallons of bleach to chlorinate everywhere, which can be extremely hazardous to their health,” Shaughnessy said. “The thing to remember when cleaning surfaces is the virus is very susceptible to common disinfectants, soap and water. This thing isn’t that hard to inactivate and to kill.”
Facts based on science and research
Shaughnessy has shared his expertise across the country and internationally on studies related to COVID-19. More recently, he has provided webinars for more than 2400 researchers and practitioners from state and federal agencies in 40 different countries. He has spoken with media about mitigation and best practices in order to lessen the spread of the novel coronavirus.
“Now is not the time to let down our guard. There is no overnight cure or fix for this virus, just common sense,” Shaughnessy said. “These issues I am bringing up are based on science and research we’ve been doing for years. Let’s accept the virus for what it is and let’s take steps to make it safer — not only to protect workers but also to protect customers.”
