Our indoor and outdoor air contains suspended biological particulate matter that can pose a threat to public health, UV filtration is one technology used to inactivate these pathogens. The airborne transmission of these infectious agents has been well documented over the years and the possibility for adverse health effects associated has increased public concern. The risks these bioaerosols impose on human health has led to an effort to create control devices and equipment to remove and/or inactivate disease-causing agents from indoor air. To reduce the concentration of bioaerosols within an indoor environment and to protect those who come into close contact with infectious persons, many facilities look to ultraviolet germicidal irradiation (UVGI) to reduce the spread of airborne infections.
Contrary to mechanical filtration products like high-efficiency HEPA filters, UV air filtration employs the use of a UV-C light lamp to inactivate pathogens and microorganisms. UV-C light is responsible for the main disinfectant activity of UV air purification systems. The energy produced by these systems can change the molecules that absorb it, with DNA being particularly susceptible to these changes. Ultraviolet light is suggested to bombard microorganisms around the UV lamp and damage the DNA they need to live.1
In-room air cleaning has been used to effectively reduce indoor particle concentrations in many settings and can be achieved by operating devices that circulate room air through fiber filter medium. However, it is suggested that some bacterial and fungal spores captured in air filter medium can survive over prolonged time periods under certain environmental conditions, and retain potential for microbial growth. Using UV filtration, it is suggested that these bacterial and fungal spores can be disinfected after exposure to the UV lamp for some time.2
Is UV Air Filtration effective in reducing airborne infectious agents?
Forrest Fencil, President of UV Resources insists that the installation of UV-C filtration systems is a low-cost, effective means for reducing concentrations of airborne and surface pathogens that lead to certain infectious diseases.
“There are three primary means of applying UV-C systems against infectious agents: upper-air, air-handler unit airstream disinfection, and surface irradiation. One of the most effective strategies is to combine upper-air UV-C units to kill airborne microorganisms along with UV-C lamps installed within HVAC systems to provide supplemental airstream kill ratios and on all plenum surfaces.”3
This information is consistent with ASHRAE’s Position Document on Airborne Infectious Diseases, that covers the spread of infectious disease from an infected individual to a susceptible person by small airborne particles (an aerosol) that contain microorganisms. In a 1959 study of influenza prevention within this document, a Veterans Administration nursing home identified an 80% reduction in influenza in staff and patients using upper room ultraviolet germicidal irradiation (UVGI).4 This suggests that air currents to the higher-room areas where the UVGI was present carried the airborne infectious particles, and they were inactivated.
Further, ASHRAE proposes several ventilation and air-cleaning strategies to reduce the concentration of airborne-infected particles. It is suggested that “personalized ventilation systems that supply 100% outdoor air, highly filtered, or UV disinfected air directly to the occupant’s breathing zone may be protective as shown by CFD analysis.”5 In addition, this document proposes two viable UV strategies, (1) installation into air handlers and/or ventilating ducts and (2) irradiation of the upper air zones of occupied spaces with shielding of the lower occupied spaces. Both configurations have been shown to remove some disease-transmitting organisms.
Utilizing UV-C radiation with other airborne infectious disease control
Because the ability of a UV-C filtration system to inactivate airborne infectious agents is likely increased with prolonged exposure to the radiation, some studies suggest a combination of UV filtration and indoor air cleaners is most effective in removing these pathogens. One study from the Journal of Occupational and Environmental Hygiene, looked to test the ability of both air cleaners and UV-C lamps with regards to bacteria and fungi inactivation.
In this study, Kunjundzic et all conducted experiments investigating the effects of UV-C radiation that showed that the lamp inactivated bacteria cells and fungal spores captured on the air filter medium surface. Tests with a filter-immobilized bacterium showed that it took 60 min to inactivate 97% of bacteria cells retained on the air filter medium. Exposure for 90 min completely inhibited the recovery of bacteria cells from the air filter medium. Tests with the fungal spores showed that 75% inactivation of fungal spores on the air filter medium took approximately 60 min and exposures at 120 min completely inhibited the recovery of fungal spores from the air filter medium.
The application of UV filtration with regards to COVID-19
There is no evidence specifying that COVID-19 is an airborne-transmitted disease as of yet, but there are certain circumstances where COVID-19 can be spread throughout the air. Because of this, UV radiation may be a viable solution to incorporate into current isolation techniques like negative pressure rooms. It is important to consult with leading experts in disease control before tacking on any of the precautions mentioned.
Tri-Dim Filter Corporation has HEPA filtration machine paired with a UV lamp to deactivate harmful contaminants from an infected individual’s room. This machine can be used as a negative pressure machine to ensure cross-contamination is not a threat in your healthcare facility. Read their product page to learn more about this useful product.
Disclaimer: Our team does not claim to be medical professionals, but simply experts in building operations and management as it applies to creating a safe indoor environment for all. Our updates are based on the latest research available to the public, and we are constantly looking to improve the relevancy the content we share.