Ultraviolet (UV) lights can be used to kill microorganisms such as viruses, bacteria, mold and fungi. They first found commercial popularity for use in water treatment facilities to remove mold, mildew and other biological contaminants from water and surrounding equipment. The technology was then introduced into the HVAC market in order to help prevent the spread of infectious disease in hospitals, doctor’s offices and other medical facilities. As a result of its effectiveness, it has become more widespread in both commercial and residential HVAC applications

In residential applications, we typically install the UV light (commonly referred to as a “stick light”) near the coils to prevent mold or bacterial growth. In addition to killing organic growth on the surface of the coil and housing, the UV light can also sanitize the air that crosses its path. With adequate exposure, the light can kill airborne bacteria, mold, fungi and some gasses without restricting airflow. Because air must come into close contact with the light in order to be decontaminated by it, it has a less immediate effect on indoor air quality throughout the rest of the space.

For this reason, we also recommend installing a UV light system in the supply side of the unit (in the ductwork) to further treat the air as it leaves the coil and eliminate any mold growth on the outside of the coil and supply plenum.

Hydrogen peroxide molecules (hydroperoxides) occur naturally in the atmosphere and help to clean the air. By releasing them into the indoor environment, the UV light facilitates constant air purification throughout the conditioned space—killing up to 99% of viruses, bacteria and mold and also reducing odors. As an added benefit, the hydroperoxides also pass a charge to allergens—such as dust, dander, pollen and other particulates—which causes them to stick together and makes them easier to filter.

We recommend keeping the fan on constantly or setting a circulating fan to come on every 30-45 minutes to help alleviate the build-up or hydroperoxides in the duct system. This helps keep the air throughout the home clean at all times (not just when the system is operating) and also reduces the build up or hydroperoxides in the duct work, which can cause strong oxidation odors when the system first starts running.