Indoor air quality and UV treatment

Air purification
Are you considering having a UV light installed to improve your indoor air quality or prevent biological growth (including mold) in your HVAC system? Read more to find out the truth about UV air purification and what you need to know before you spend your hard-earned money. If you need information about indoor air quality click here.

UV purification is widely misunderstood, and we hear of this misconception on a regular basis. Many contractors and technicians assume that a UV light located in the air stream, or near the evaporator coil, will purify the air in your home or building and that's all you need to know, but this is simply not true.  UV light will only disinfect the surfaces where the light shines and putting one in your system could actually damage your equipment. Let’s look at both of these important factors.


1. UV light will only disinfect the surfaces where the light reaches.

The evaporator coil is where biological growth easily thrives in an AC system and it is not uncommon to see it also spread through out the entire duct system. The humidity level and "food" sources are there as a result of normal functions of the AC.  In a system that has not been maintained the humidity levels are often higher which supports yet more growth.

To be effective at reducing or eliminating biological growth in the evaporator coil the UV light needs to contact every face of the coil.  In most cases this will require 2 UV lamps, one above and one below the coil.

A UV light directed at the coil has been shown to "kill" biological growths in the same manner as natural UV light from the sun but it will also dry out plastics and that is item 2 that needs to be considered.





2. UV light degrades plastics and one of your systems critical components is very likely made with non UV resistant plastic.

Have you ever noticed something plastic that has been sitting in the sun light for a long time which was brittle or cracked?  This is typically considered a result of photodegradation and photo-stabilization of polymers.

Very few indoor units are designed to withstand exposure to UV, and only recently have more manufacturers started to address this issue. The reason this is a problem is the drain pan (the thing that collects water from your evaporator coil) is almost always going to be made of plastic which can crack if exposed to UV for long periods of time.

Granted, it will take 3 to 5 years of exposure before the cracks develop and by then who is going to think that it was the UV light installed years ago that caused the problem.

If a crack develops in the drain pan the water normally collected will leak into your unit and onto anything else below.

So what’s the answer?  There’s 2.




First let’s consider what’s really going on. Why do you want a UV light? Is it biological growth on your coil, or to disinfect the air? If the purpose is to prevent biological growth, then you are barking up the wrong tree. In order to thrive, biological growths need moisture and the evaporator coil is the perfect place for it if it isn’t working properly.  You see, the coil should not be holding water it should be removing water through the drain. If the moisture levels are high enough to encourage biological growth, then something else isn’t right. It could be the system is too large for the home or building, the filters are not being changed often enough, the static pressure of the air is too high, the drain line is clogged or there is outdoor air making its way into your duct system. Most often it is a combination of several factors.

To summarize, reduce the moisture content in the air by having a properly sized and sealed system, perform thorough and regular maintenance and make sure the drain line stays clear.

• If your desired purpose for the UV light is to disinfect the air, then you should look at the different types of solutions and choose one based on your particular situation. 

One of the most effective solutions is a system that produces an oxidizing plasma also called photo-hydro-ionization. Photo-hydro-ionization is a process first used commercially by the RFG environmental group. The unit creates an advanced oxidation plasma (AOP) that is distributed through the duct system into the conditioning living space, all the way back to the evaporator coil. Unlike passive air technologies, such as an electrostatic filters, which need pollutants to pass through the unit for purification or filtration, the AOP sweeps through the home or building actively purifying pollutants at the source. The AOP consists of hydro-peroxides, oxide ions and hydroxide ions which are all friendly oxidizers that are found in nature’s process of cleaning the outdoor air and are safe for humans and animals alike.

RGF’s systems produce this oxidizing plasma as a small UV light shines on a metal that acts as a catalyst. The plasma that is created travels throughout the entire envelope of the home or building and effectively disinfects the air as well as surfaces. These units are much more expensive than a conventional UV bulb, but they are truly superior and in a league of their own.

The Guardian Air QR+ utilizes RGF’s patented PHI-Cell® technology and is easily mounted into an existing air conditioning and heating system’s air ducts.

These units are air purifiers and not filters. It does not reduce particulate matter like dust. For an air purifier with added particulate reduction that is even more effective at removing allergens, you’ll want to have a look at the REME HALO®.

Again, you must consider why you want this unit and if it is truly worth the cost to you. If you are suffering from health issues that you suspect are related to your indoor air I will recommend the same thing I always recommend to our customers. Talk to a practitioner about exercise, eating habits, gut flora, lifestyle changes, getting more fresh air and having some tests done to see what you are possibly reacting to. Hopes deferred make the heart sick and I don’t ever want to tell our customers that we have the answer when we truly don’t know what the real problems are. We work on HVAC equipment, not people.