The C wavelength of the UV spectrum targets the DNA of microorganisms. This destroys their cells or makes duplication impossible. Pointed at a cooling coil or drain pan, UVC energy rids the surface of biofilm. This is a gluey matrix of microorganisms (bacteria, fungi, debris, et al.) that grows when in contact with moisture. Biofilm is common in HVAC systems and leads to a host of indoor air quality (IAQ). UVC also destroys airborne viruses and bacteria that disperse and move through an HVAC system. UVC light was created in the 1880’s and later commercially used to destroy waterborne viruses and bacteria in 1909. By the 1930’s surgeons where using UVC light in operating rooms to reduce airborne bacterial and viral infections.

Ultraviolet (UV) lights have been used since the 1930s in commercial and industrial locations including sanitizing meats and vegetables, medical applications, air treatment, and water treatment. Residentially they started to show up as in-duct air purifiers in the early 1990’s and today there are manufacturers joining the trend. UV lights are a proven technology, yet they must have the right wavelength and have enough power for surface kill of biological growth, as well as airborne control of micro-organisms and germs.

What to look for when buying a UVC System

To make sure you’re getting what you paid for when choosing UV lights to install into your HVAC system the light must have a UVC germicidal wavelength lamp and enough microwatts of power. UV lights below 55 microwatts of power have little effect for this, 70 – 180 microwatts is recommended.
Outside the sun emits wavelengths of light that serve many purposes in our outdoor environment: helping plants grow, producing vitamin D in the skin, skin tanning, kill germs and deodorize the air.


These wavelengths are broken down with separate measurements each serving a different function and they are measured in nanometers (nm). The Ultraviolet (UV) spectrum consists of UVA, UVB, UVC, and VUV (or UVV). Visual light is above 400 nm and the UV spectrum ranges from 400 to 10 nm as depicted below:

UV lights are effective, but they work in a specific range. They’ll kill organic growths, such as mold or bacteria, but they have no effect on dust or other allergens. In residential cases, an HVAC company will install the UV light near the coils to prevent mold or bacteria growth as air passes through. Since all of the air passes through the coils, this also kills growths in the air. UV lights are the most effective in humid climates, where evaporator coils can easily get wet.


By controlling surface and airborne microbes, UVC can be beneficial in many ways, including Indoor Air Quality (IAQ) control and energy savings:
IAQ Control. UVC improves air quality by preventing the spread of airborne viruses and reducing the allergy and asthma symptoms triggered by mold. It creates safer and more comfortable indoor environments, resulting in a happier and healthier home for you and your family.

Energy Savings. Studies show that even a thin (.024″) layer of biofilm buildup on a coil increases energy consumption by 21.5%. UVC provides continuous cleaning of coils to rid biofilm more effectively than regular cleaning methods. Field data from UVC commercial and healthcare installations has shown resulting HVAC energy savings ranging from 10% to 28%.