Implementing Portable Air Purifiers
Ultraviolet germicidal irradiation can destroy airborne pathogens
With new strains and variants of COVID-19 appearing in the United States and in news coverage, there has been a renewed focus on indoor air quality. Medical and dental practices are looking for additional ways to create office environments where patients and employees can feel safe and comfortable.
In early 2020, my partner and I had to temporarily close all three of the offices of our oral and maxillofacial surgery practice in suburban Birmingham, Alabama, as a pandemic-related precaution. But when we reopened, and patients returned for procedures, we implemented numerous safety measures.
Like many of our fellow healthcare providers, we followed all of the recommended steps to protect our staff and patients from COVID-19, including implementing expanded personal protective equipment, appropriately distanced furniture and equipment, frequent surface cleaning, temperature checks, and wellness questionnaires. However, as it became clear that the virus spreads through the airborne transmission of aerosols, I wanted to take the extra precaution of adding air purifiers to the waiting rooms to supplement the filtering capacity of our facilities' HVAC systems.
According to the US Environmental Protection Agency, when used properly, air purifiers can help reduce the number of airborne contaminants, including viruses, in a home or confined space. This recommendation has been echoed by state health departments and state dental associations as well.
During my research process, I learned that there are three primary technologies available in portable air purifiers that effectively address viruses such as SARS-CoV-2-the organism that causes COVID-19. The first and most common one is HEPA filter technology, which uses woven material to collect particles and remove them from the air. The other two technologies, ionization and ultraviolet germicidal irradiation, use negative ions to cause airborne particles to stick to surfaces and shortwave ultraviolet light (UV-C) to inactivate or destroy viruses, respectively. Each technology offers advantages but also comes with drawbacks. For example, HEPA filters need to be replaced periodically and can be expensive, some ionization filters produce harmful ozone as a by-product, and UV-C light can be harmful if not properly concealed.
Ultimately, I settled on UV-C technology for its ability to destroy pathogens rather than simply filter them from the air. The fact that UV-C light has been used as a disinfecting technology in hospitals for years provided me with an extra layer of confidence in its efficacy. Our practice purchased and implemented two UV-C air purifier units. These units have quiet fans that draw air in, expose it to a powerful UV-C bulb long enough to deactivate any viruses and germs, and release it back into the room. They kill up to 90% of pathogens on the first pass, and their effectiveness increases with each subsequent pass.
When choosing an air purifier, it is important to select a unit with a filtering capacity that matches the size of the space it will be sanitizing. The units that we selected were the appropriate size for our practice, circulating the air in a 10 ft by 10 ft room four times in 1 hour and exceeding the recommendations of ventilation experts.
The patient response has been extremely positive. Although we are often asked what the units are, when we tell patients that they are UV-C air sanitizers, many express their appreciation that we have taken an extra step to protect them. In fact, we have noticed that patients often sit close to the units to increase their comfort and peace of mind while they are waiting for their appointments.
Patients may be acting on instinct when they sit close to the units, but this behavior aligns with the science, according to Chris Hogan, PhD, an engineering professor at the University of Minnesota and the editor-in-chief of the Journal of Aerosol Science. Portable air purifiers have been shown to create microenvironments around them, which means that the air that is closest to the unit is the cleanest and likely has the least number of contaminants. He notes that it's important that the flow rate of the unit increases the ventilation rate in the area for it to be effective.
Whatever our new normal becomes when the COVID-19 vaccines have been fully deployed, we know that concerns about airborne pathogens will remain, so we'll likely continue using these filters to assure our patients that we are doing everything we can to keep them safe and healthy when they are visiting us.
About the Author
Christopher Kahn, DMD, maintains an oral and maxillofacial surgery practice in Birmingham, Alabama.