Selection Guide: Ultraviolet Germicidal Lamp

SELECTION GUIDE: Ultraviolet Germicidal Lamp ® Selection Guide: Ultraviolet Germicidal Lamp Table of Contents Introduction . 4 What Is Ultraviolet-C? . 5 Electromagnetic Spectrums . 5 Types of UV Electromagnetic Energy . 6 Absorption and Scattering Processes . 6 . .Absorbtion and the Ozone . 7 . .Ozone Generators as an IAQ Tool . 7 UV-C Usage . 8 UV-C Benefits and the IAQ Problem . 9 Identification of IAQ Contaminants . 10 Gases . 10 Particles . 10 Sources of Contamination . 11 Contaminant Effects on HVAC Systems . 12 Solutions for HVAC Contaminants . 12 Ultraviolet Germicidal Irradiation . 13 Biofilm Source Control - Methods and Benefits . 16 Other Methods for Bioaerosol Control . 17 Carrier UV-C Germicidal Lamp vs. Other Commercial UV-C Lamps . 18 Application of Carrier UV-C Germicidal Lamps to HVAC Systems . 19 Carrier UV-C Germicidal Lamp Location . 20 General Installation Guidelines . 21 Protecting Man-Made Materials from UV-C Energy . 21 Maintenance and Cleaning Recommendations . 22 Summary . 23 References . 24 3 Selection Guide: Ultraviolet Germicidal Lamp Introduction One of the most significant issues for today’s HVAC (Heating, Ventilation, and Air Conditioning) engineer is Indoor Air Quality (IAQ). Many building owners, operators, and occupants complain of foul odors emanating from HVAC systems. The objectionable odor is the byproduct of the microbial growth (mold and fungus) that accumulates and develops on wet surfaces of HVAC units, causing foul odors to emanate from affected systems and degrading the IAQ and unit performance. This objectionable odor has been appropriately named the “Dirty Sock” syndrome. Less obvious to the building occupants, but of equal importance, are the physical effects the microbial organisms have on HVAC equipment. They restrict the airflow and limit the heat transfer capability, which increases the operating costs of the equipment. Fortunately, IAQ degradation, foul odor, and increased expenses can be eliminated with the installation of the ultraviolet ‘C’ band (UV-C) lamps. The ultraviolet germicidal lamps are designed to kill odor causing mold and fungus that grow in wet evaporator sections of HVAC units. These lamps are installed inside HVAC systems and irradiate areas inhabited by the offending organisms, making it impossible for them to survive. The organisms disappear, the odors disappear, and most importantly, the IAQ complaints disappear. This guide will discuss the microbial growth and IAQ contaminant problems in the HVAC industry, the UV-C lamp and other possible solutions, and the benefits of using Carrier’s UV-C lamp. 4 Selection Guide: Ultraviolet Germicidal Lamp What is Ultraviolet-C? Ultraviolet-C (UV-C) is one form of electromagnetic energy produced natu- rally by the sun. Artificially produced UV-C energy aids in enhancing Indoor Air Quality (IAQ) by eliminating microbial organisms that grow on wet surfaces of HVAC systems. Electromagnetic Spectrums The sun, a thermonuclear reactor system, produces a spectrum of electromagnetic energy which ranges from cosmic rays to radio waves. We are casu- ally aware of portions of this electromagnetic spectrum, such as the infrared portion, which warms the earth, and the visible light portion to which our eyes respond allowing us to see. Ultraviolet energy is also a portion of the sun’s electromagnetic spectrum. The UV region (excluding vacuum UV) is defined as that portion of the electromagnetic spectrum with wavelengths between 200 and 400 nanometers (nm). UV-C, also known as “Short Wave UV,” has wavelengths of between 200 nm and 290 nm (Fig. 1). FIG. 1 — SOLAR ENERGY 5 Selection Guide: Ultraviolet Germicidal Lamp Types of UV Electromagnetic Energy The use of various forms of UV energy is quite common in our everyday lives, some of which require special care when used since they can be potentially harmful. It is therefore important to be familiar with these forms of UV energy, their uses, and their dangerous effects on humans when not handled properly. Three forms of UV energy are discussed below. UV-A energy is the primary energy component used in tanning beds. UV-B energy is used as a treatment for skin conditions such as psoriasis. Prolonged exposure to UV-A and UV-B energy can lead to skin cancer and has been shown to contribute to the incidence of cataracts.1 UV-C energy, when used with the proper safeguards, is relatively harmless to humans, although prolonged exposure may cause temporary reddening of the skin and/or temporary conjunctivitis. Absorption and Scattering Processes As stated previously, the sun emits a variety of energy forms, some forms of which are harmful to the complex molecules necessary for earth’s lifeforms. The harmful forms are the ultra short-wave radiation that includes X-rays, gamma rays, and ultraviolet radiation. Due to the distance between the earth and the sun, only some of the energy emitted by the sun reaches the earth’s surface, minimizing the intensity of harmful particle radiation. Fortunately, the distance is appropriate for the infrared and visible light necessary for pho- tosynthesis and life as we know it. Solar energy that reaches the earth’s atmosphere interacts with the molecules in the atmosphere by the processes of absorption and scattering. In the process of absorption, molecules absorb the solar energy and convert it to heat. In the scattering process, solar energy is reflected by gas molecules, dust particles, and water vapor. The blue color of the sky is due to the scattering process. Shorter wavelength (blue) light is scattered more effectively than the longer wavelengths, making the sky appear blue. Figure 2 compares the amount of solar energy reaching the earth’s atmosphere to the amount that actually penetrates to the earth’s surface. Entering Earth's Atmosphere 0.25 Difference due to absorption and 0.2 scattering by gases in atomosphere, such as Reaching Earth's Surface 0.15 ozone, etc. 0.1 Main Output of W/cmˆ2-nm 0.05 UV-C Lamps, 254nm 0 0.0 200.0 400.0 600.0 800.0 1000.0 Wavelength of Sunlight , nm FIG. 2 — SOLAR RADIATION ENTERING EARTH’S ATMOSPHERE AND REACHING ITS SURFACE 6 Selection Guide: Ultraviolet Germicidal Lamp Absorption and the Ozone The ultraviolet radiation that reaches the upper atmosphere is also impacted by the absorption process. A key component in absorption of ultraviolet energy is ozone (O3) in the upper atmosphere. Oxygen (O2) from the upper atmosphere absorbs ultraviolet energy with a wavelength less than 242 nm (UV-C and Vacuum UV). The result is the disassociation of the O2 molecule, allowing the formation O3. The O3 in turn absorbs ultraviolet energy with wavelengths 242 nm to 320 nm (UV-C and UV-B) converting the O3 back to O2 and O. This continual process limits the amount of potentially damaging ultraviolet energy reaching the earth’s surface to very low levels. It is therefore very important to maintain the ozone layer in the upper atmosphere. In order to preserve our environment, including the O3 in the upper atmosphere and its beneficial effects, Carrier Corporation and others have significantly reduced the use of ozone depleting compounds. Ozone Generators as an IAQ Tool Although ozone is a very valuable component in the upper atmosphere, it is considered a pollutant at ground level. According to the United States Environmental Protection Agency2, “When inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath, and throat irritation. Ozone is a toxic gas with vastly different chemical and toxicological properties than oxygen. Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants.” Ozone belongs in the upper atmosphere, not in our homes and offices. 7 Selection Guide: Ultraviolet Germicidal Lamp UV-C Usage When ultraviolet light is used on the earth’s surface correctly and with appropriate safeguards, it can be extremely beneficial as a germicidal tool. The germicidal effects of ultraviolet light were first noticed and actively studied by a Danish physician, Niels Ryberg Finsen (1860-1904), in the 1880’s. Dr. Finsen had noticed a connec- tion between exposures to the sun’s rays and a stimulating effect on human tissue. His work lead to the development of the Finsen curative lamp, a device that produces artificial “sunlight.” This “sunlight” also contained UV light. The Finsen curative lamp remained in use as a healing aid through the 1950’s (Fig. 3). The key portion of Dr. Finsen’s discovery was that light, ultraviolet light, has the ability the destroy pathogenic organisms.3 The importance of Dr. Finsen’s work was recognized in 1903 when he was awarded the Nobel Prize for Medicine. FIG. 3 — FINSEN CURATIVE LAMP Today we recognize that ultraviolet light, specifically UV-C with a wavelength of approximately 260 nm, has a pronounced germicidal effect. We have also learned that mercury has a natural spectral line of 253.7 nm and if vaporized in plasma will emit UV-C energy at approximately 254 nm. These discoveries lead to the development of the first commercial UV-C germicidal lamps by the lamp division of Westinghouse in the 1930’s. The Westinghouse lamps were used pri- marily in hospital environments through the 1950’s. The challenge today is to utilize the germicidal capability of UV-C energy in the HVAC industry. 8 Selection Guide: Ultraviolet Germicidal Lamp UV-C Benefits and the IAQ Problem To fully understand the potential for UV-C energy as a tool in the IAQ struggle, it is appropriate to briefly examine the IAQ issue and the attempts to define “quality air.” ASHRAE standard 62-1989 (Fig. 4) defines quality air as, “Air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.”4 FIG.

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