UV for Improving IAQ and HVAC System Efficiency

There are many factors that can contribute to poor indoor air quality, but microorganism growth in HVAC systems is a one of the worst offenders. Damp, humid conditions around condenser coils and condensate pans encourage biofilm growth, which, left unattended, can choke airflow, decreasing HVAC system efficiency up to 40%, and cause microbes to enter the airstream. Some of these microbes can land in the duct system and colonize, causing even more contaminants to enter conditioned space.

One of the many methods of preventing or killing microbial contaminants is the application of ultraviolet light, also known as ultraviolet germicidal irradiation (UVGI). When microorganisms such as bacteria, viruses, mold, yeast and protozoa are exposed to UV radiation, their DNA and RNA are inactivated, effectively rendering them unable to reproduce. UV had long been used for equipment sterilization and water purification, so it was reasoned that it could be used for HVAC as well. Two UVGI types were developed – coil treatment and in-duct treatment, which are often used in tandem. Coil types are more effective, as coil exposure and drain pan exposure to UV light is continual, whereas in-duct system exposure time is limited to the time it takes for the airstream to pass the light source. Manufacturers can improve in-duct UVGI efficacy by adding more bulbs to subject microbes to higher UV dosage. Independent studies have shown microbe kill rates to be about 98%. Some systems capture hardier microorganisms in a filter exposed to more UV light, increasing system efficacy.

Until recently, much of the available data as to the effectiveness of UVGI was largely anecdotal. But as the technology increases in popularity, more and more substantial evidence is emerging to show that a well-designed UVGI system can be highly effective in eliminating cooling coil biofilm, improving IAQ, and improving system efficiency when used in conjunction with traditional preventive maintenance.

MSC - Mechanical Service Corp.
41 South Jefferson Road
Whippany, NJ 07981
973-884-5000
http://www.mscnj.com