Do UV systems for air conditioning systems work?





Yes and No!

I have intended to write something on this subject for quite some time.  I am seeing more and more UV lights and seeing a big push by companies selling them. It is very hard to find anything objective on them.  A quick internet search will yield mostly adds and articles by people selling the UV systems.  So here is my opinion.

The HVAC (heating ventilation and air conditioning) market place, like most others, is more competitive than ever.  Successful companies have learned to focus on sales of “add on items”.  This Philosophy isn’t all bad if the items offered are of value or need to the customer and do what the brochures claim.

The purpose of this article in not to overwhelm you with my ability to throw out numbers and “techy” sounding terms.  The purpose is to educate consumers on the UV light products.

Germicidal UV lights are effective at killing biologicals such as germs, mold, and bacteria.  The effectiveness of this depends on several factors.  The three main factors are the power of the UV light, how close the light is to what you desire to kill, and exposure time.

UV cannot kill what is not directly shining on, much like I am not going to get a sunburn in my house.  A UV system can be effective at killing mold etc. that is very near the bulb and has direct light exposure.  The claim of many that it will keep any mold off an air conditioning cooling coil is false unless it was completely bathed in light.  This would require multiple bulbs.

One commonly cited study claims a UV system killed 99.9% of MSRA bacteria.

This is extremely misleading.  The test cited used five bulbs, fifty inches long in a reflective tunnel.  This is an 1100 watt industrial system.  This is not what you would install in your home.

The big problem is exposure time! We are talking now about the claim that UV systems can kill mold, germs and bacteria throughout your house.

Exposure of biological (mold etc) to the UV in an average running air conditioning system will be .24 seconds!  That is nowhere near the exposure time needed to kill your targets, even at very close proximity to the bulb. Eight inches from the bulb and you are 25 times less effective!

In summary my opinion is on residential UV systems is not favorable.  The UV technology is sound and very effective for certain industrial and commercial uses.

The typical UV systems sold to homeowners are nowhere near as effective as their hype claims.  I have never installed one at my house.  I could buy UV systems at wholesale price and install myself in my house but I never have.  They have very little benefit.

There are better Indoor Air Quality alternatives.

Gary Poe

Poe Air

Fort Worth, TX


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