Mold spores are encountered everywhere in our homes and workplaces. The majority of molds are not a source of irritation because we encounter them in small concentrations. However, when mold spores find the right environment - damp and dark conditions - they will multiply to the point of affecting HVAC performance and possibly occupant health.

Fortunately, there is a low-cost, easy-to-maintain, energy-efficient solution for eliminating mold growth in HVAC systems - ultraviolet (UV) germicidal lamps.

How Mold Affects HVAC Performance

Biological growth (mold, bacteria, etc.) is produced in the damp, dark environments found on cooling coils, fins, and drain pains within HVAC systems. This biological growth establishes a thin film on coils that grows into thicker colonies and accumulates fine particulate material. As this film continues to develop, HVAC performance decreases due to restricted airflow and reduced heat transfer. Essentially, equipment fans and compressors have to work harder resulting in a significant increase in kW and kWh operating costs. As mold growth on a coil increases, energy costs increase due to reduced coil efficiency.

Immediately after a coil is cleaned manually, efficiency begins to decline due to mold growth. UV germicidal systems keep coils continuously clean, allowing coils to operate at near-peak efficiency.

How Mold Affects Occupant Health

Air flowing through coils and across drain pans spreads mold spores throughout buildings where the spores land and multiply. When spread through the air stream, mold can adversely affect air quality, which in turn may impact occupant health. Poor indoor air quality can aggravate asthma and upper respiratory systems, as well as contribute to fatigue and sinus irritation - all of which can decrease employee performance and increase absenteeism.

Traditional Coil Cleaning Increases Maintenance Time And Costs

Traditionally, coils have been hand-cleaned by shutting down the cooling coils while maintenance personnel use harsh cleaning chemicals to remove biological growth. Not only does this stop HVAC system operation, it exposes staff to mold and chemicals - again, endangering health.

Another alternative is pressure washing. This form of cleaning pushes mold into the coil interiors, reducing coil efficiency or eventually requiring coil replacement. Cooling coils can also be removed and submerged; however, this is an expensive way to clean coils. All of these traditional cleaning methods require coils to be cleaned by personnel on a regular basis.

Any building with damp or wet cooling coils can benefit from UV germicidal systems.

UV Lamps Increase Efficiency, Reduce Maintenance

Ultraviolet germicidal lamps are a cost-effective, low-maintenance alternative for cleaning coils. UV germicidal systems reduce or eliminate biological growth by immersing cooling coils in UVC germicidal light.

Biological growth is particularly susceptible to a narrow spectrum of ultraviolet band light. This spectrum in the "C" band is referred to as UVC band light. UVC penetrates the microbe's shell, damaging the DNA and stopping cell reproduction. Exposure over time continues cell destruction to the point where it is easily removed via normal condensate flow.

Not only do UV systems minimize mold that moves into the air stream, but they increase HVAC performance and reduce the need for equipment maintenance and coil replacement.

The UVC energy that is directed at the cooling coils and drain pans eliminates mold, allowing your HVAC system to operate at peak performance. Since the UV system is in effect continuously cleaning the coils, there is no longer a need to manually clean coils - reducing maintenance costs and coil shutdown.

In new HVAC installations, UV germicidal systems maintain coils in like-new condition. For retrofit installations, the UV lamps clean and maintain coils on a continuous basis.

UV lamps have been used for over 70 years in hospitals, laboratories, food technology, and other critical applications to clean, disinfect, and sterilize. Now other commercial and institutional facilities are using UV lamps more frequently due to their positive effects on indoor air quality and HVAC performance.

Lynne Wasner is a technical writer for Dristeem Corp. and has been writing about HVAC issues, technical products, and the built environment for 20 years. Reprinted with permission from Dristeem's UV Bulletin. For more information on UV germicidal systems, visit or call 800-328-4447.

Publication date: 08/22/2005