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More than 100 years ago it was discovered that ultraviolet light kills germs. This discovery has led to the use of ultraviolet lights for all kinds of uses: sterilizing hospitals, sterilizing water, germicidal lamps in food establishments, and even curing nail polish faster.


It was obvious then that someone would figure out that UV light can be used to improve indoor air quality for residential HVAC systems. Let’s go over the technology of UV lights for indoor air quality and the types of UV lights available for residential HVAC systems.

Is It True that UV Lights Can Really Help My Air Quality?

The UV light can help eliminate many types of fungi, bacteria, germs, viruses and pathogens. Usually, the UV lights are installed within the air handler, which remains turned on 24/7. The HVAC UV lights are effective at controlling mold inside the air handler, as all mold in line-of-sight of the UV bulb will be killed, keeping the coil mold-free.


Few important factors will affect the effectiveness of the UV lights installed in your HVAC system, like the intensity, number, placement and direction of UV lamps. The surrounding temperature and humidity levels of your home and the reflectivity of surrounding surfaces will also have an impact.


What Types of UV Lights I Can Use with My HVAC System?


There are two types of UV lights for HVAC systems, Coil Sterilization and Air Sterilization.

  • In Coil Sterilization, a “stick type” light is installed inside the return air duct and sterilizes the air handler coil. A coil sterilization UV light runs 24/7 and is the most common type of HVAC UV light. It is also the most affordable option.

  • In Air Sterilization, a complete UV light unit sterilizes the moving air. The UV light unit is installed in the return air duct and cycles on with the air handler blower.

Lifetime, Installation and Cost of UV Lights


Placement of the UV light is important for high effectiveness. The UV purification lights must be mounted next to the evaporator (cooling) coil and on the downstream (cold air side) of the coil. The UV rays must shine both on the air conditioner cooling coil and on the water drain pan underneath the coil (if installed) because this is the main area where mold spores grow.


If the UV lamps are mounted elsewhere, then slime, algae, bacteria, and mold can grow on the cooling coil, drain pan, and even the blower and duct work. As a consequence, these organisms will contaminate the air that you're breathing, throughout your living space.


The negatives of a UV filtration system are that it can sometimes be costly as it is a newer form of air purification. Depending on your area and the available models nearby, you should be able to find a system that meets your budget while still maintaining air quality needs.


Functionally, UV systems are designed to work with a particle filter rather than as a stand-alone item, so regular filter replacement or cleaning is still required.


In addition, the UV bulbs will need to be replaced every 12 to 36 months, depending on the model. One UV stick light bulb is estimated to last 9000 hours, just over 1 year. Replacement bulbs cost about $90 and replacing the bulb during each annual HVAC service and maintenance is nearly effortless.

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