In a May 7 New York Times article, researchers discussed the use of ultraviolet light in combating infectious pathogens. “We have struggled in the past to see this highly effective, very safe technology fully implemented for airborne infections,” said Dr. Edward A. Nardell, a professor of global health and social medicine at Harvard Medical School. “We’ve done the studies. We know it works.”
The article notes that UV light “mangles the genetic material in pathogens — DNA in bacteria and fungi, RNA in viruses — preventing them from reproducing.” “You’ve killed it essentially,” said William P. Bahnfleth, a professor of architectural engineering at Pennsylvania State University.
In a March 9 article in the HVAC trade publication ACHRNews, industry experts noted that ultraviolet (UV) light treatment can complement filtration by addressing the particles that can slip through filters. “UV germicidal systems have also been shown to reduce microbial load and pathogens that are found within the HVAC system and drain pan that would otherwise be introduced and distributed throughout the envelope of the building,” the article quoted Aaron Engel of indoor air quality equipment manufacturer Fresh-Aire UV as saying. UV treatment systems can be used in homes and commercial buildings.
His opinion was seconded by Bahnfleth, who noted that, “Even HEPA filters that have been tested in the laboratory with viruses will have some level of penetration…not much — a few percent. But if anything gets through and if it's a very virulent pathogen, that means you're not perfectly protected against infection by that filter.” Hence the complementary UV system to catch those that slip through.
As noted above, UV light treatment can be used as a supplement to filtration, killing pathogens that escape. Daniel Jones, president of UV Resources, a UV light treatment equipment company, touted upper-air UV-C fixtures as a commercial building remedy for viral droplets: Airborne droplets containing infectious agents can remain in room air for six minutes and longer,” he said. “Scientists have found that COVID-19 can remain infectious on surfaces at room temperature for up to nine days. Upper-air UV-C fixtures can destroy those microbes when they are exposed to the UV-C energy in a matter of seconds.” He pointed to kill ratios of up to 99.9 percent on a first-pass basis that have been modeled, and concentrations are further reduced each time the air circulates.