Field Controls: About UV Air Purification

Indoor Air: High Concentrations of Biological Contaminants
With tighter building construction in recent years, the quality of indoor air has declined dramatically.

The air circulating in the ductwork of the average home or office can be concentrated with contaminants including molds, bacteria, viruses, and dust mites. We fill our lungs up to 20,000 times each day. Over time, these contaminants can cause inflammation of the mucous membranes, upper respiratory problems, asthmatic conditions, headaches, and flu-like symptoms.

Filtering systems offer little or no help because these airborne contaminants either pass through the filter or simply collect on the filter medium, creating a breeding ground. Now, with the UV-Aire® Air Purifying System, a solution is available to directly address the problems associated with poor indoor air quality.

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The Sun: Nature’s Outdoor Air Purifier
For years, scientists have known that one of the most effective air purifiers is natural sunlight. Not the light we see when we look out the window, but the invisible “C” band, ultraviolet rays that make up part of the sun’s light spectrum. The sun’s UV-C rays act as a natural outdoor air purification system, inhibiting the growth and reproduction of bacteria, viruses, fungi, molds, and dust mites. However, this natural process does not occur indoors. Ultraviolet radiation (UV-C) replicates the natural outdoor purification system of the sun by destroying the illness and disease-causing microbes living and multiplying in indoor air. In combination with a quality filter, it is the most effective way to reduce airborne contaminants and the health risks they represent.

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Facts About Indoor Air:

• According to the Environmental Protection Agency, the air in homes can be up to 100 times more polluted than outdoor air.
• The National Academy of Sciences Institute of Medicine reports that exposure to indoor pollutants is a key contributor to the asthma problems of this nation.
• Most allergy and asthma sources are passed from person to person through the air.
• The air in a single room can contain hundreds of thousands of infectious bacteria, viruses, fungal spores, and contaminants, which can only be seen with a microscope.
• Health effects may show up immediately, or after years of exposure to poor indoor air quality. These symptoms include some respiratory diseases, heart disease, and cancer. They may be severely debilitating or fatal.

 

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Facts About UV:

• The disinfection of medical equipment using UV has been a common and reliable practice.
• UV disinfection has been determined to be adequate for inactivating bacteria and viruses.
• The germicidal effects of UV light cause photochemical damage to DNA and RNA within microorganisms.
• “...ultraviolet radiation, properly integrated with heating, ventilating, and air conditioning systems, shows the most promise as a widely applicable means of air disinfection.” Richard Riley, M.D.

 

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Indoor Air Treatment With UV.
UV’s effectiveness in killing bacteria is directly related to a microorganism’s exposure time. Indoor air in a typical residential forced-air HVAC system will be recirculated 40-75 times a day. With a UV generating lamp mounted in the HVAC duct, cumulative exposure can be very effective in controlling indoor bacteria.

UV rays will also kill germs that breed in drain pans and A-coils. Properly positioned, an ultraviolet system can significantly reduce indoor air contamination and prevent the growth of new microorganisms.

The treatment of indoor air with ultraviolet radiation has been successful in health care facilities, food processing plants, schools, laboratories and other applications. It is safe, silent, and proven.

Since direct exposure to UV light can cause skin cancer and blindness, the most practical application of UV light in the home or office is in the main air distribution (heating and/or air conditioning) system. As UV light will not pass through metal, glass, or plastic, a UV light can be installed in the main supply or return duct of a central heating or air system without concern for direct exposure to eyes or skin. This is an ideal location since the air in the home or office will pass through the HVAC system up to 75 times per day during normal operation, and as many as 150 times per day in continuous fan mode.

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Filter Systems Alone Don't Solve the Problem.
The majority of indoor air is conditioned by forced-air heating and cooling (HVAC) systems. Standard fiber air filters are entirely ineffective in trapping germs, as most particles are simply too small, passing through the porous filter. New, high efficiency style filters will only capture airborne bacteria down to a certain size. These high efficiency filters are nominally effective, trapping small airborne contaminants on the filter, creating a breeding ground where germs can continue to grow and multiply.

HVAC systems are a dark and damp breeding ground for mold and bacteria, particularly at the system filter and air conditioning A-coil. The buildup of matter on the A-coil and filter can significantly reduce the efficiency of the appliance by constricting and reducing air flow. This means increased cost to the homeowner in addition to the risk of airborne pollutants.

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How Much UV Energy is Required to Kill Bacteria?
Most, if not all, bacteria can be destroyed by the use of UV light. The main factors in disinfection are the amount of UV power the lamp produces and the length of time the bacteria is exposed to the UV light source.

The energy required to kill microorganisms is a product of the UV light’s intensity and exposure time. This energy is measured in microwatt seconds per square centimeter.

Intensity x Exposure Time = microWatt seconds/cm2

Table 1 lists the amount of UV energy (measured in µW-sec/cm2) necessary to destroy various bacteria.

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Independent Lab Testing.
Independent lab testing of the UV-Aire shows that in a single-pass air flow test, one 18-inch UV-Aire lamp can reduce levels of Serratia Marcescens (a typical bacteria) by 93%, while a two lamp system can reduce by 99%.

The calculated average UV energy output levels of a single UV-Aire lamp in an 18-inch square duct is 2,608 µW-sec/cm2 and 6,186 µW-sec/cm2 for a two lamp system. The 6,186 is comparable to the 99% energy required for Serratia Marcescens. It can be seen that there is a direct correlation between the UV-Aire UV lamp output and the observed kill rates in the lab.

Bird Flu Virus (H5N1). The Bird Flu is a type of influenza. Laboratory tests have indicated the kill rate for the influenza virus is 6,600 microwatts of UV energy, and it is reasonable to conclude that the Bird Flu virus can be reduced or eliminated by exposure to UV-C light 6,600-10,000 microwatts.

UV lamp intensity is rated at a distance of one meter. To determine the intensity of ultraviolet radiation at different distances from the lamp, multiply the intensity of the lamp by the intensity factor shown in the models and specifications chart.

Example: To determine the ultraviolet intensity of the UV-18 at a distance of six inches, multiply 73 by 20 to yield 1460 µW-sec/cm2.

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Correlating The Lab Test With Other Bacteria.
Harder to kill bacteria and molds require greater energy or exposure time to be as effective. For example, 99% reduction of Rotavirus requires 24,000 µW-sec/cm2 of UV energy versus 6,600 µW-sec/cm2 for Influenza virus. This means that Rotavirus spores are five times more resistant than Influenza. Consequently, Rotavirus spores will require five times the UV output energy from the lamp or five times greater exposure time.

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Surface Test: UV Kills and Prevents Mold on A-Coils

A specific test was designed to determine UV’s effectiveness in treating mold on coil surfaces. The test simulated the damp, dark settings where A-coils are found. In this study “We took a standard A-coil, sterilized it, introduced two kinds of mold, and then placed it in a controlled, moisture-laden environment,” says Bernard Kane, of Microbe Management. “We created two

separate chambers in our lab. One chamber was bathed in UV light. The other was not.” The results were dramatic and conclusive. The side of the A-coil that was exposed to the ultraviolet light was clean and clear of mold growth. Mold continued to grow unabated on the side without UV. Subsequently, the contaminated side was bathed in UV light and the mold was eradicated. Kane summarized the results: “Properly positioning a UV lamp over the A-coil in a residential or commercial air conditioning system can eliminate surface mold on the coil and prevent future mold growth as well.”

 

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Airborne Testing: Single Pass and Cumulative Tests
Bacteria and viruses are introduced into the building by its occupants and often cannot be controlled at the source. Therefore, it is important to attack these airborne invaders early and often, before they have an opportunity to multiply. The single pass test proves that UV effectively kills these airborne microorganisms in the duct.
Since HVAC systems typically re-circulate the air 40-75 times per day, a multi-pass, cumulative test was also conducted. Results demonstrate that repeated, multi-pass exposure to UV light dramatically reduces the concentration of bacteria and viruses throughout the home.

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Single Pass Test: UV Deadly for Airborne Microbes
This study introduced a common bacterium into a galvanized air duct equipped with a UV light to determine how effective the lamp would be in reducing the bacteria with one exposure, or a “single pass.” The tests were conducted at two speeds: 1125 cfm and 2250 cfm in an 18" x 18" duct. The UV lamp yielded at least a 90% reduction of the test bacteria with a single airflow pass at 1125 cfm, and at least 71% reduction at 2250 cfm.

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Cumulative Tests: Multiple Exposures Dramatically Improve IAQ
To further investigate the effectiveness of UV on indoor air quality, Microbe Management created a series of tests designed to measure the cumulative effect of UV in reducing airborne contaminants. The tests were performed in a structure with two isolated 8' x 8' x 8' rooms where air could be sampled. In the control room, no UV was present, while the other room utilized a portable UV air purifier. According to Bernard Kane, Ph. D., of Microbe Management, “Test results were very encouraging. In both rooms, we introduced a resistant, spore-forming bacteria until the air was saturated with 350 colonies per cubic foot. In the room with the portable UV unit, the spore count was reduced by 50% in just 10 minutes and by 98% within 30 minutes. In the control room, without UV, more than 85% of the bacteria were still active after thirty minutes.” Similarly, the leading consumer UV “tower” model was also tested, but showed only minimal effectiveness. (See chart below.)

 

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Conclusion: UV Is An Effective Part of “Whole House” Solution
A-coil irradiation, single pass, and cumulative tests confirm that UV is an important and effective contributor to a healthier home environment. UV technology used with a quality filter (MERV rated 8 or higher) will dramatically improve Indoor Air Quality. Additionally, portable units can be used in combination with in-duct models. This combination is strongly recommended for individuals with depressed immune systems, asthma, allergies, or other respiratory conditions. For homes without forced-air, portable UV air purifiers are recommended to enhance IAQ. Also, health care professionals, teachers, and day-care workers can benefit from additional UV protection from influenza and other viruses.

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