What is UV-C? Ultraviolet light (UV-C) is a powerful disinfectant. Its usefulness in medical and research environments has expanded to HVAC systems where UV-C light combats microorganisms to improve efficiency and indoor air quality (IAQ).

 History of UV Light Use for Disinfection

Ultraviolet light has been used to sterilize equipment in hospitals and research labs since the 1930s. In the 1990s there was a push to use UV-C to improve indoor air quality by reducing the microbial build-up within HVAC coils. In 2013, the Centers for Disease Control and Prevention (CDC) participated in a study on eliminating some “superbugs” common in hospital rooms using a disinfection system featuring germicidal UV-C light.

Studies have been done by Duke University Medical Center and the National Center for Biotechnology Information to determine whether UV light actually helps to remove fungal contamination and other harmful airborne particles from the air. The results were quite positive. In both studies, UV-C light led to significant reductions in contamination.

Types of UV Light

Scientists divide light into subtypes based on wavelength. Ultraviolet light has shorter wavelengths than visible light and is further divided into UV-A, UV-B, and UV-C light. UV-A is the least harmful type and has the longest wavelength. It is commonly referred to as “black light.” UV-B causes sunburns with extended exposure and increases the risk of skin cancer. Approximately 95% of this type of UV rays is absorbed by the ozone layer of the Earth’s atmosphere and never reaches Earth.

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UV-C light has the shortest wavelength and is the most harmful type of UV light. Because UV-C light disintegrates the nucleic acids in the cells of microorganisms, it is used to sanitize food, air, and water. It can even be dangerous to humans if not used properly. Almost all the naturally occurring UV-C light is absorbed by the Earth’s atmosphere.

How UV-C Lamps Operate

UV-C light at appropriate dosages can eliminate many types of fungi, molds, bacteria, viruses as well as other microorganisms. With proper light placement, all pathogens can be eliminated from air passing through an HVAC/R unit.

How UV-C Light Improves Airflow and Heat-Transfer Efficiency

Over time, mold and fungi grow on HVAC/R coils and surrounding areas, reducing airflow and undermining unit efficiency. Installing UV-C lights in the duct system or within the coil system of an HVAC/R unit offers a highly effective layer of protection from many harmful airborne microorganisms. Placing UV-C lighting within the coil system has the added benefit of destroying the mold and fungi that grow on coils and restrict airflow. This upgrade can restore coils to installation levels of efficiency, significantly increase airflow, and reduce energy use by up to 35%. An HVAC/R unit augmented with UV-C light will last longer and require less maintenance because it does not have to work as hard to move air through the coils.

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UV-C Light Can Lower Costs Associated with HVAC/R Systems

Cost savings associated with a properly installed UV-C light result from increasing the operating efficiency and reducing the energy use of HVAC/R units, and cutting down on lost work hours due to illness by maintaining a healthier environment for the public. Bulbs are rated for approximately 9000 hours of use–or a little more than one year running 24 hours a day, 365 days per year. A regular replacement schedule must be followed to ensure the efficient operation of the HVAC/R system.

 Contact Therma to learn how UV-C light can be most effective in your HVAC system.

Sources and Further Reading:

Centers for Disease Control – New CDC Study Confirms Effectiveness of UV-C Disinfection to Combat Harmful Pathogens

Science Daily – Ultraviolet light effective in hospital infection control, study suggests — ScienceDaily

National Library of Medicine – Effectiveness of Germicidal UV Radiation for Reducing Fungal Contamination within Air-Handling Units – PMC

Stanford Solar Center – UV Light – Stanford Solar Center

NADCA White Papers – Restoring Energy Efficiency Through HVAC Air Distribution System Cleaning | National Air Duct Cleaners Association (NADCA)

ACHR News – UV-C Light Benefits in HVAC Applications | 2014-01-06 | ACHRNEWS

ACHR News – UV-C Systems for Commercial HVAC | 2014-07-14 | ACHRNEWS

Ultraviolet.com – Microorganisms Inactivated by Germicidal UV Light

Lincoln Tech Blog – Facts About HVAC UV-C Light Air Quality Benefits