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Should You Install A UV Germicidal Light Inside Your Air Conditioner?

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You've probably heard of the saying "sunlight is the best disinfectant" before. That's because sunlight really is a good disinfectant—or at least the invisible ultraviolet energy that's given off by the sun. That explains why moss never grows in sunny areas and why you need sunscreen whenever you want to spend the entire day out in the sun.

UV germicidal lights are intended to prevent algae, mold, and other biological contaminants from growing inside of your air conditioning system. The following explains how these devices work, the benefits they can offer to your air conditioner, and the caveats you should be aware of prior to purchase and installation.

Understanding the Power of UV Radiation

To understand how UV germicidal lights work, it's important to understand how UV radiation works in general. There are three types of UV radiation: UV-A, UV-B,and UV-C. UV-B is the most dangerous of the lot, since it can cause sunburn and even increase your chances of developing skin cancer with prolonged exposure. UV-A is a bit more benign, but it can still cause premature skin aging with prolonged exposure.

UV-C is the most interesting of the three since it features the germicidal qualities needed to deal with mold, mildew, and algae. UV-C radiation is capable of damaging cells on a truly microscopic level by breaking up the cell DNA's molecular bonds. These bonds are replaced with thymine dimers that repair the DNA, but can sometimes leave it too damaged to function properly, resulting in cell death and eventual death of the organism in question.

How UV Germicidal Lights Work

While UV-A and UV-B rays are in plentiful supply, the vast majority of UV-C rays emitted by the sun end up being absorbed by the Earth's atmosphere before they can reach the ground. Fortunately, the effects of UV-C radiation can easily be replicated with the help of a specially-designed fluorescent light bulb. These bulbs contain a small amount of mercury at low to medium pressures. When excited by electrical current, it produces light at the wavelengths needed to create UV-C radiation.  

UV germicidal light bulbs shouldn't be mistaken for blacklight bulbs. The latter contains a special phosphorescent coating that produces UV-A radiation, plus certain materials and creatures that have a natural bioluminescence will also glow when exposed to a UV-A lamp. UV-C light bulbs don't contain that phosphorescent coating, allowing them to generate the UV-C radiation that makes them more appropriate for use as a passive form of disinfectant.

UV germicidal lights are commonly installed in very close proximity to an air conditioner's evaporator coil. In some cases, there could be as many as three separate lamps surrounding all three sides of a typical evaporator coil for maximum coverage.

Pros and Cons

There are plenty of advantages to using UV germicidal light bulbs inside your air conditioner:

  • Constant exposure to UV-C light makes it completely impossible for mold, mildew and algae to take hold on the evaporator coil or any other surface that's exposed to the light.
  • UV-C light also destroys bacteria and viruses, thus creating a healthier indoor environment by lessening the spread of common germs.
  • A cleaner coil also means a cleaner condensate drain tray, which in turn means fewer drainage issues, accidental spill-overs, and time-consuming cleanups.

However, there are also a few caveats to consider:

  • UV-C can only travel so far without becoming ineffective at disinfecting surfaces. For this reason, your lights must be positioned only a couple of inches away from the surface.
  • Most UV germicidal lights aren't effective at treating moving air. However, there are UV-C light systems that are designed specifically with flowing air in mind. These units are usually found inside of return air vents and other areas of your ductwork.
  • Constant exposure to UV-C light can degrade certain types of plastic, especially non-UV stabilized plastics.

In the end, it's up to you to decide whether you should make a UV germicidal light a new addition to your air conditioner. Contact a local air conditioning service for more information.