Education is a must with these air-quality devices.

A UVDI V-RAY GRID maintains the cooling coils at Denver Center for Performing Arts. Photo courtesy of UVDI


The most important new product to enter the indoor air quality market since the invention of the electronic air cleaner more than 50 years ago is the ultraviolet lamp.

So I guess that statement spills the beans about my answer to the question raised in the title of this article. But why do I say that? Because mold allergies are one of the most common ailments, the wet environment inside an air-conditioning evaporator coil is a prime area for cultivating and spreading mold throughout a whole building, and ultraviolet lamps kill mold!

However, the installed cost of an ultraviolet lamp isn’t what most homeowners object to. It’s the fact that the bulbs need to be replaced every year or so by a technician, and they (and the service call) aren’t cheap. In other words: They aren’t something that the homeowner can have installed and then forget, or wash out periodically, like you can with EACs. So when the home or building owner looks at the total cost of installing and operating such a system, they often balk at the purchase.

Yet, they do the job! And if the service company that does the installing handles the matter correctly by adding the price of the bulb to an annual or semiannual maintenance agreement where there is no added cost for installing a new bulb (since they’re servicing the equipment already), this is a win-win situation. The customer saves and the service company is more likely to sell the agreement!

Why shouldn’t homeowners or company maintenance people change their own bulbs? Well, they could if they comprehend the hazards and they know what to do. They must understand that there is some shock hazard in the wet, metal environment, and the UV light can quickly damage their eyes. So in most cases, this work is best left to professionals.

The nice thing about UV bulbs is that they not only destroy mold inside the A/C cooling-coil area, but they destroy all sorts of living organisms in the air (including bacteria); and by killing mold and bacteria, they tend to keep the condensate drains clean and running free.

Wrong applications

Unfortunately, UV bulbs are also frequently used to solve A/C mold problems that should be fixed first.  UV bulbs are frequently used by contractors and service companies to kill mold in the ductwork downstream from the evaporator coil; and that’s a problem which needs to be corrected by other means.

Understand that mold will only grow where it’s wet; the ductwork and its insulation downstream from the evaporator should never be wet! The only means by which it can get that way is by water droplets blowing off of the evaporator coil, which is a fixable condition. There is just too much air velocity through the evaporator coil.

When adding ozone is appropriate

There are, of course, situations where high air velocity across an evaporator coil can’t be easily fixed, and this may result in mold growth. So what some contractors have chosen to do is install UV bulbs on both sides of the coil. Sure, this works, but it doubles the install and servicing costs for the customer. However, they can use special UV bulbs that produce ozone instead (UV bulbs naturally tend to do that), and the ozone will kill the downstream mold.

I don’t recommend the use of ozone-producing bulbs where there is no downstream mold growth because ozone is a bleaching agent that can harm the lungs. But when there is a serious living organism (such as mold) involved, the harmful output is minimal.

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