
FAQ
Infection Control
According to the U.S. EPA, a professionally designed UVGI system “can effectively kill the virus that causes COVID-19 and help protect people from the disease indoors.”[1, 2]
It is important to note that science has not found any microorganism that can withstand the destructive effects of the UV-C germicidal wavelength, including superbugs and other antibiotic-resistant germs. In fact, viruses and bacteria cannot develop a resistance to germicidal UV because it uses energy to kill, rather than synthetic or chemical elements. Today, there are several approaches to using this decades-old technology to reduce microbes in the air and on surfaces, including airstream disinfection (also known as in-duct) and upper-room decontamination.
Germicidal UV-C air disinfection systems are installed in a building’s HVAC ductwork to disinfect moving airstreams before they reach employees. Kill ratios over 99 percent on a first-pass basis have been demonstrated by the Environmental Protection Agency (EPA) and the National Homeland Security Research Center. As air is re-circulated, concentrations of infectious pathogens are further reduced by each subsequent pass (“multiple dosing”).
Upper-room UVC is the oldest disinfection application of the germicidal wavelength for airborne inactivation and is recommended for improved control of highly contagious airborne diseases such as Tuberculosis by the U.S. Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health.
[1] National Academies of Sciences, Engineering and Medicine. Does ultraviolet light kill the coronavirus? October 2020. Retrieved from https://sites.nationalacademies.org/BasedOnScience/covid-19-does-ultraviolet-light-kill-the-coronavirus/index.htm
[2] U.S. Environmental Protection Agency. Frequent Questions about Indoor Air and Coronavirus (COVID-19) What is Upper-Room Ultraviolet Germicidal Irradiation (UVGI)? What is HVAC UVGI? Can either be used to disinfect the air and help protect myself from COVID? Retrieved from
https://www.epa.gov/coronavirus/what-upper-room-ultraviolet-germicidal-irradiation-uvgi-what-hvac-uvgi-can-either-be
Because most viruses can be transmitted via air and direct contact, it could be presumed that HVAC systems can inadvertently broadcast the infection, increasing its spread. Therefore, facility managers should consider employing both upper-room UVGI and HVAC germicidal fixtures to ensure the greatest mitigation practical for control of microbes and airborne microorganisms in communal spaces.
Airborne droplets containing infectious agents can remain in room air for 6 minutes and longer. Upper-room UVC fixtures can destroy those microbes when they are exposed to the UVC energy in a matter of seconds. Kill ratios up to 99.9 percent on a first-pass basis have been modeled and, as air is recirculated, concentrations are further reduced by each subsequent pass (“multiple dosing”).
Surface-cleaning UV-C systems provide 24/7 irradiation of HVAC/R components to destroy bacteria, viruses and mold that settle and proliferate on HVAC coils, air filters, ducts and drain pans. UVC prevents these areas from becoming microbial reservoirs for pathogen growth that can eventually become airborne and circulated by HVAC systems.
A system installed for HVAC surface irradiation, while not specifically designed for it, can also provide first-pass kill ratios of airborne pathogens of up to 30 percent, along with the primary benefits of restored cleanliness, heat-exchange efficiency and energy use.
Technology
Microorganisms are simple organic structures that readily absorb the UVC wavelength, causing photo-disassociation (destruction). A microbe’s DNA (deoxyribonucleic acid, is first to be adversely affected due to its weaker molecular bonds.
In hundredths of a second, it suffers irreparable damage. The subsequent loss of genetic instructions causes cell death and/or the inability to replicate, rendering them harmless. Continuous exposure causes uninterrupted degradation, such as the sun does, only significantly faster.
Research
The CDC [v] and ASHRAE have recommended UVC as one technology that can “reduce the risk of dissemination of infectious aerosols in buildings and transportation environments.” [vi] ASHRAE has recognized that the 253.7 nm germicidal C-band wavelength inactivates virtually all microorganisms living on HVAC/R surfaces with a kill ratio of 90 percent or higher, depending on UV-C intensity, length of exposure, lamp placement, and lamp life cycle. In fact, a CDC-funded study conducted in two hospitals found that UVC reduced the total number of colony-forming units of any pathogen in a room by 91 percent. [vii]
Science has yet to find a microorganism that is immune to the destructive effects of UVC, including superbugs and all other antibiotic-resistant microbes associated with healthcare-associated infections.
[v] CDC. COVID-19 Employer Information for Office Buildings (September 11, 2020). Retrieved from https://www.cdc.gov/coronavirus/2019-ncov/community/office-buildings.html [vi] ASHRAE Position Document on Infectious Aerosols (April 14, 2020). Retrieved from https://www.ashrae.org/file%20library/about/position%20documents/pd_infectiousaerosols_2020.pdf [vii] Anderson D. J., et. al. (2013) Decontamination of Targeted Pathogens from Patient Rooms Using an Automated Ultraviolet-C-Emitting Device.” Infection Control & Hospital Epidemiology. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3703853/