by Donna Rider

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Ultraviolet light is a misunderstood and under-utilized tool for improving indoor air quality. There are various reasons to take advantage of the possibilities that UV lighting provides. It is used in hospitals and research labs to sterilize equipment and rooms, and scientists have yet to find even a superbug that is resistant to UV-C rays.

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 “super bugs” common in hospital rooms using a disinfection system featuring germicidal UV-C light.

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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 rays led to significant reductions in contamination.

Various Types of UV Rays

The types of ultraviolet light:

—UV-A light is the least harmful type and has the longest wavelength. It is commonly referred to as “black light.”

—UV-B light causes sunburns with extended exposure and increases the risk of skin cancer. Approximately 95% of this type of UV ray is absorbed by the ozone layer of the Earth’s atmosphere and never reaches Earth.

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

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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 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 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 lighting within the coil system has the added benefit of destroying the mold and fungi that grow on coils and restrict airflow, and this upgrade can restore coils to installation levels of efficiency and significantly increase airflow. An HVAC/R unit augmented with UV-C will last longer and require less maintenance, because it does not have to work as hard to move air through the coils.

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

Cost savings associated with the use of properly installed UV-C light result from increasing the operating efficiency of HVAC/R units, the reduction of lost work hours due to illness, in addition to the wider benefits that accrue from 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 adhered to ensure efficient operation of the HVAC/R system.



Donna Rider is a Technical Writer with more than 18 years of experience researching, developing, managing and producing on-line documentation and training videos. Ms. Donna Rider gained her expertise in technical writing during her highly successful career in several leadership roles. Ms. Rider wrote technical documents to assist the Help Desk Technicians troubleshoot calls from customers at Gateway and Wells Enterprises.