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UV Light Uses For Schools And Universities
Roughly 55 million students and seven million staff attend the 130,000 public and private schools each day in the United States. At any given time, each of those people are susceptible to various types of illness, many of which are communicated through the air.
Ironically, the transmission of infectious airborne diseases such as tuberculosis, influenza and the common cold can be accelerated or controlled by a school or college’s HVAC equipment.[i]
In a recent article published in American School and University magazine, UV Resources President Dan Jones suggests that school facility and maintenance directors adopt active infection control protocols to reduce disease transmissions.
According to Jones, one such control, ultraviolet germicidal irradiation (UVGI), can be applied to continuously reduce, or in some cases prevent, infectious pathogens from growing on or circulating in school air and surfaces.
UV-C FOR INFECTION CONTROL
UVGI or ultraviolet light in the 254-nm germicidal C-band wavelength (UV-C) kills all known microorganisms, including bacteria, viruses, molds and other pathogens – even those immune to antibiotics, known as superbugs.
The benefits of UV-C’s efficacy in inactivating pathogens are explored in two ASHRAE Position Documents. The documents find that the UV-C wavelength kills 90 percent of all microorganisms living on HVAC air ducts and evaporator coils, depending on light intensity, length of exposure, UV lamp placement and lamp life cycle. Moreover, UV-C continues to destroy pathogens 24/7/365, as air cycles through an air handling unit (AHU).
The first means of applying UV-C in schools is through upper-air units.
Upper-air (upper-room) UV-C units have been in use since the 1930s and can be installed in classrooms, cafeterias, gymnasiums, locker rooms, childcare centers—anywhere infectious agents may exist.
These systems work by creating an irradiation zone within the upper region of most any space. As convection or mechanical air currents lift airborne infectious agents into the upper air (above 7-8 feet), they are exposed to the UV irradiation where they are killed.
Upper-air UV-C units kill pathogens circulated into its irradiation zone by drafts, pressure differentials or the movement of people, such as entering, exiting or cleaning a room. UV lamps are also effective against droplet nuclei from coughing or sneezing.
HVAC Coil Irradiation
The second means of applying UV-C in schools is through HVAC coil irradiation.
HVAC systems provide an excellent growth area for mold and some bacteria in and around cooling coils, drain pans,[i] plenum walls and filters. Growth of these microbial deposits also leads to coil fouling, which will increase coil pressure drop and reduce airflow and heat exchange efficiency.[ii]
UV-C systems applied in this manner can also provide first pass kill ratios of airborne pathogens of up to 30 percent.[iii] Another benefit of installing UV-C within HVAC units or duct runs is its ability to prevent the recirculation and re-transmission of harmful microorganisms within a space.
Besides improving indoor air quality, the hidden value of UV-C’s use in HVAC systems is its ability to improve airflow, boost heat exchange efficiency and reduce maintenance needs.[iv] It accomplishes this veritable HVAC hat trick for an average equipment cost of less than $0.15 per cfm. Moreover, the cost of the efficiency-enhancing UV-C equipment is a mere fraction of the 10-35 percent potential reduction in energy and maintenance costs it offers.
UV-C installations are a simple, effective and relatively inexpensive means for schools to improve indoor environmental quality. Infectious diseases such as tuberculosis, influenza and the common cold are transmitted via airborne and surface pathogens.
Because ultraviolet germicidal irradiation kills all known microorganisms, the technology can be applied to continuously reduce, or in some cases prevent, infectious pathogens from growing on or circulating in school air and surfaces.
To view the original version of this article, as it appeared in American School & University, please click here.
- The History of Ultraviolet Germicidal Irradiation for Air Disinfection; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789813/
- UV-C Light Used to Disinfect High School After Reported Illnesses;
[i] ASHRAE. 2014 ASHRAE Position Document on Airborne Infectious Diseases. www.ashrae.org/about-ashrae/position-documents
[i] Levetin, E., R. Shaughnessy, C. Rogers, and R. Scheir. 2001. Effectiveness of germicidal UV radiation for reducing fungal contamination within air-handling units. Applied and Environmental Microbiology 67(8):3712-3715
[ii] Montgomery, R. and R. Baker. 2006. Study verifies coil cleaning saves energy. ASHRAE Journal 48(11):34-36.
[iii] Fencl, Forrest. 2015. “UV-C And Hospital Infection Control.” Engineered Systems 72-79. http://digital.bnpmedia.com/publication/?i=241409&p=78
[iv] ASHRAE. 2015. ASHRAE handbook—HVAC applications (ch. 60.8). Atlanta: ASHRAE. https://www.ashrae.org/resources--publications/handbook/description-of-the-2015-ashrae-handbook-hvac-applications