HVAC systems can be a blessing or a curse when it comes to disease transmission and infection control. In fact, according to ASHRAE, the transmission of infectious airborne diseases such as tuberculosis, influenza and the common cold can be accelerated or controlled by a building’s HVAC equipment.[i]
In other words, the same system that circulates air through a building can also circulate bacteria and such diseases as measles, tuberculosis and Q fever.
The same 2014 ASHRAE Position Document on Airborne Infectious Diseases notes that the foundation for any infection control strategy begins with a “well-designed, installed, commissioned and maintained HVAC system.” Said differently, a building’s HVAC system is ground zero when it comes to reducing disease transmission.
- The ASHRAE Position Document states four ways in which an HVAC system can promote indoor environmental quality and, indirectly, building occupants’ overall health.Supplying clean air to occupants susceptible to illness
- Containing/exhausting contaminated air outside the building envelope
- Diluting or filtering indoor air with clean outdoor air
- Cleaning indoor air
A number of strategies can be used to achieve the above conditions, ranging from ventilation to pressurization. Perhaps the most effective method for cleaning indoor air through an HVAC system, however, is ultraviolet-C (UV-C) technology. And, at an average of $0.15 /CFM, Ultraviolet Germicidal Irradiation might be the most affordable means of improving indoor air quality (IAQ) and reducing disease transmission.
UV Lighting for HVAC Systems
Light in the UV-C wavelength eliminates and/or prevents the buildup of organic material on the surfaces of cooling coils, drain pans, and interior duct surfaces. This improves airflow, returns and maintains the heat-transfer levels of cooling coils to “as-built” conditions and reduces maintenance.
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).
UV-C’s ability to decontaminate the air flowing through a building’s HVAC system can be most beneficial where communicable diseases are more common, such as office buildings, schools, healthcare settings, municipal offices, etc. An improperly maintained HVAC system in these environments can promote disease transmission as it recirculates those same germs throughout the building. Conversely, installing UV lamps, with their ability to kill all known microorganisms, can prevent disease transmission and/or cross contamination.
In addition to improving indoor air quality, UV-C can yield other HVAC UV light benefits when installed in a building’s air handler including maximizing HVAC system efficiency, thereby reducing energy use and costs.
[i] ASHRAE. 2014 ASHRAE Position Document on Airborne Infectious Diseases. www.ashrae.org/about-ashrae/position-documents