More than 150 years ago, researchers found that uvc filtration was an effective way to disinfect surfaces. Healthcare facilities and water purification systems have made wide use of UV-based systems, and managers have specified them for building HVAC systems to keep cooling coils free of biological growth.
UV light is effective against viruses because it damages a virus’s DNA and RNA, making it inactive. While UV light wavelengths range from 10 to 400 nanometers (nm), it has been shown that UV-C with a wavelength of 200-280 nm is the most effective at destroying viruses. With enough intensity and a long enough exposure, UV-C can destroy up to 99 percent of exposed viruses.
While minimizing biological growth on coils has been the primary application for using UV-C in HVAC systems, the pandemic has focused attention on using UV-C light to destroy the virus within the HVAC system’s airstream. UV-C fixtures can be installed in HVAC system ductwork — typically, close to the coil — so they can expose pathogens in the airstream and any that might have grown on the coil. Because their effectiveness in destroying pathogens is directly related to the exposure intensity and duration, managers should plan the installation carefully.
UV-C light is harmful to eyes and skin and can cause permanent damage, so it is essential that installers provide protection for maintenance personnel. This means providing automatic shutoff switches on all access panels near the lamps, installing UV light-blocking filters on all inspection windows, and training personnel who might be working on the HVAC system in the vicinity of the lamps.
UV-C in-duct systems offer several advantages. Their installation and operating costs are low. They can destroy pathogens within the system. They also are effective in preventing a buildup of biological material on system coils, improving IAQ and system performance.
