At the Crescent Avenue Christian Preschool in Buena Park, Calif., the young students receive an extra measure of protection against infectious diseases: ultraviolet-C or UVC lamps installed in the air conditioning system for IAQ and mold control. Since the school installed the devices, the director has cited reductions in illness, as measured by a 20-percent drop in absenteeism among students and a 50-percent drop among teachers. During a particularly bad flu season, students and teachers at the facility experienced some colds, but not the serious fevers and flus reported by other schools in the area.

Such reports are common from those who operate schools equipped with UVC protection. At the time of this writing, school officials are concerned not only with the usual seasonal colds and flus, but with the looming threat of a bird or avian flu pandemic. Bird flu is a virus; and if or when it achieves the mutated form that is expected to cause a pandemic, it will be highly infectious, with the capability to spread person-to-person through the air.

How do lamps in the air conditioning system keep a school healthy? These devices rely on UVC energy, the most germicidal wavelength in the ultraviolet spectrum. Installed in an air handling system, UVC lamps emit enough energy to penetrate even the tiniest microbe to destroy its DNA and RNA, killing or deactivating it. In this manner, UVC effectively stops both surface organisms that grow inside heating and air conditioning systems and airborne microbes that circulate through these systems.

Bird flu and other viruses are tiny microorganisms that can measure as little as 0.02 micron — too small to be captured by conventional air filters. In a typical school environment with four to five air changes per hour, UVC energy destroys more than 90 percent of flu viruses and other microbes with each pass. In doing so, UVC reduces the number of infectious microbes to a level significantly below what it would take to infect most people — including young children, whose immune systems are not fully developed.

Because it destroys the DNA and RNA of microorganisms, UVC works against all strains of influenza, as well as other viruses including colds, SARS, measles and German measles; and infectious bacteria including TB, Legionella, pneumonia and whooping cough.

UVC is also an effective weapon against another common cause of unhealthy air in schools: mold. The allergy-asthma symptoms triggered by mold and mold spores, and the resulting complaints and litigation that may occur where severe mold infestations exist are well documented.

Though water infiltration is blamed as the culprit, mold actually originates deep inside the air conditioning system, where the cool, moist conditions provide an ideal environment for its growth. Mold rapidly builds up on A/C coils and releases spores that travel from the coil through the airstream and into the occupied space. Mold and its byproducts account for much of the illness and discomfort in schools today and many of the maintenance and operational headaches.


nstalled on the downstream side of the cooling coil, UVC lamps eradicate both surface and airborne mold contamination, reducing the upper respiratory symptoms and unpleasant odors associated with mold. At the Rizzuto Elementary School in Texas, for example, various mold remediation methods were unsuccessful until the school installed UVC lamps. The devices helped solve a costly maintenance problem while eliminating complaints from this campus.

Similarly, at the Stepping Stones Center in Cincinnati, UVC reduced the need for several other remedial measures in a building where mold was discovered. When the school found that remediation costs would be considerably lower, they were able to use the funds instead to expand and upgrade the building.

Usable in All Types of School Systems

Many classrooms and other school areas are equipped with unit ventilators, fan coils and other room unit air handlers. These packaged systems present a special IAQ challenge because most have tight space constraints and can only be equipped with low-efficiency filters that do not effectively capture infectious disease contaminants or mold.

UVC lamps provide an effective solution, because the devices can be configured for use in systems with limited space and/or access. In fact, from the smallest packaged room unit to the largest central air handling system, you can add UVC protection without having to make any costly modifications to the air handler itself. The germicidal effect is virtually immediate and continuous, as long as the lamps are kept on 24 hours a day with the fan running.

What about the cost? Fortunately, the benefits of UVC extend beyond IAQ and infection control. UVC lights keep coils, drain pans and other components clean and free of organic buildup, eliminating the time, cost and potential hazards associated with chemical cleaning programs.

At the Iolani School in Honolulu, the maintenance department eliminated an $8,000-a-year coil cleaning program through the use of UVC, which continuously kills the mold on the coils and drain pans, restoring them to“as new” condition. Similarly, at Robbinsdale (Minn.) Area School District 281, UVC-treated coils appear constantly clean even after three years, with no sign of mold growth — a fact verified by Petri dish testing of samples from coil surfaces. They, like Iolani, have eliminated costly coil cleaning.

By keeping components clean, UVC lamps also increase system efficiency, reducing energy and operating costs. HVAC energy savings of 15-20 percent are not uncommon. As a result, a UVC installation can often pay for itself in just months. This is good news for school administrators who want the protection but worry about the added price tag.

UVC Output: A Key to Success

UVC energy has been used for decades to kill harmful microorganisms in many applications, particularly for disinfection of drinking water and for upper-air infectious disease applications in room-temperature environments. The older-style, conventional UVC lights used in these applications, however, suffer drastic output losses when exposed to cold or moving air. As a result, in past decades UVC technology has not been popular for HVAC systems.

This situation changed in the mid-1990s, with the advent in the U.S. of a new generation of devices that were specifically engineered to provide peak output under HVAC conditions. The new-generation UVC lamps are verified to provide up to five times the output of conventional lamps under HVAC conditions.

It is critical to understand this distinction between the older and new-generation UVC devices. The reason: For UVC to be an effective weapon against the spread of infection, you must have sufficient output for the application. Always use a new-generation device capable of providing output per inch of glass of at least 10 µW/cm at 1 meter, in a 400-fpm airstream of 45° F.

Look for a device whose output has been independently tested under HVAC operating conditions: Some UVC lamps are tested in warm/still air conditions, which can yield misleading results. To get a true apples-to-apples comparison between devices, also make sure output claims are stated“per inch of glass” and are based on tests performed at a distance of one meter from the light source. Be wary if a supplier cannot provide output information based on these parameters.

ROBERT SCHEIR, Ph. D. Scheir is president and CEO of Steril-Aire, Inc., a leading manufacturer of UVC devices. He can be reached at Steril-Aire, Inc., 800/2STERIL (800-278-3745) or at <>