We often see ultraviolet (UV) lights promoted as a form of mold treatment in HVAC systems. It has been suggested that UV lights provide the only way to kill mold spores without using harsh chemicals. This claim is usually made by companies which (conveniently) sell or install UV lights.
Are UV lights an effective way to eliminate mold in your HVAC system? They can be part of the solution, but UV lights alone aren’t enough.
How UV Lights Kill Mold
Germicidal UV Lights (known as UVC lights) sterilize and kill mold spores. If powerful enough, the UV light source can kill mold spores (and other organic nuisances like viruses and bacteria). The potential danger to humans and other living things limits the power of UV lights which can be used in residential settings.
This limits the effectiveness of UV lights for controlling mold. In order to be effective, mold spores must be within 6 to 8 inches of the UV light source. The type of mold spore determines how long it must be exposed to the UV light to kill it.
UV lights are most effective when used for controlling the growth of mold on stationary surfaces rather than for mold elimination. Properly installed, they work well for preventing mold on the coils of your HVAC. They aren’t effective for mold elimination because many mold spores are airborne. They don’t get close enough to the UV light long enough to be affected.
Using UV light is never a substitute for filtration or other mold treatments. Used in conjunction with regularly cleaning or changing your filters, they can help prevent the spread of mold. Installing UV lights isn’t effective for removing house mold once it’s been established.
Types of UV Air Cleaners
There are three basic types of UV air cleaners you can use in your HVAC system. These are:
- Ozone generators. These are designed to produce ozone gas. It’s the most effective way to kill mold spores with UV light. Unfortunately, ozone gas also causes health problems. The EPA recommends not using ozone generators because of the health and safety issues associated with ozone.
- UVGI cleaners. These can be used for mold elimination on the cooling coils. They also kill some airborne mold, but should not be seen as a replacement for adequate filtration. Filters must still be changed frequently.
- PCO cleaners. These use a catalyst along with the UV light to convert pollutants into less harmful substances. They are not effective against airborne mold.
UV light is most effective when used to prevent mold from growing in your HVAC system. It is not effective for removing house mold that is already established. It doesn’t improve the quality of air in your home in and of itself. Used in conjunction with proper filtration and appropriate mold treatment, it can prevent the occurrence (or recurrence) of mold on the coils of your HVAC system.
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