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ASHRAE Lists UV Lamps a Top Strategy for Maintaining Indoor Environmental Quality
Airborne infectious diseases can run rampant in facilities, such as schools and hospitals, if not properly combated. Frequent hand washing and covering one’s nose while sneezing can only go so far, unfortunately, beckoning for a more systematic method of improving indoor environmental quality (IEQ).
The following chart from a 2014 ASHRAE Position Document on Airborne Infectious Diseases ranks various strategies for improving IEQ based on application and research priority.
In the chart, two strategies rank exceptionally high in research priority and medium to high on application priority—Upper-room Ultraviolet Germicidal Irradiation (UVGI) and Duct and air handler UVGI. Both strategies are also listed as having some of the most universal applicability.
Stated differently, ASHRAE strongly encourages the research and application of UVGI in a variety of settings—from health to correctional facilities.
ASHRAE has recognized the health benefits of UVGI and that the technology is a potentially beneficial option that facility managers should consider employing in their buildings. UVGI, also known as UV-C, uses light in the electromagnetic spectrum to kill, or prevent the growth of, virtually all known microorganisms. There are two main types of UV-C.
- Upper-room UV-C: Upper-air/room UV-C systems are installed in communal spaces, such as in patient and waiting rooms, corridors and break areas to interrupt the transmission of airborne infectious agents.
Airborne droplets containing infectious agents can remain in room air for six minutes or more. UV lamps can destroy those microbes in a matter of seconds and they operate 24 hours a day for continuous control. They are typically mounted seven feet above the floor.
The benefits of upper air UV-C’s efficacy in inactivating pathogens are well documented. A 2013 CDC-funded study conducted in two hospitals found that UV-C reduced the total number of colony-forming units of any pathogen in a room by 91 percent. Similar results of UV-C's efficacy in inactivating pathogens were demonstrated in a 2003 study in Atmospheric Environment and a 2014 American Journal of Infection Control study referenced in Infection Control Today.
-Air Handler UV-C: In HVAC systems, mold and some bacteria can grow in damp areas around cooling coils, drain pans, plenum walls and filters. Growth of microbial deposits leads to coil fouling, which increases coil pressure drop and reduces airflow and heat-exchange efficiency.
Installed downstream of the cooling coil in the direction of airflow, UV-C lamps can return HVAC systems to their original, design performance standards, or as-built conditions, in as little as 90 days and cut energy use by 10-25 percent on average. At the same time, UV lighting for HVAC systems helps prevent the same microorganisms from being recirculated into the indoor air, thereby impeding disease transmission and/or cross contamination.
For these reasons, ASHRAE states that “Building designers, owners, and operators should give high priority to enhancing well designed, installed, commissioned, and maintained HVAC systems with supplemental…UVGI.”
ASHRAE continues to study UV-C closely and is constantly updating its recommendations for the technology. Two recent ASHRAE PositionDocuments, for example, outline the benefits of UV-C’s efficacy in inactivating pathogens.
UV-C can thus be an effective means for maintaining a building’s indoor air quality, especially when combined with other strategies, such as dilution ventilation and filtration. Facility managers should strongly consider incorporating this technology into their buildings and air handlers.