ASHRAE Journal - August 2008 - (Page 36)

all operating conditions. Output variation due to air temperature and velocity is not a concern for most upper-air systems. Reflectivity References 1. 2008 ASHRAE Handbook—HVAC Systems and Equipment, Chapter 16. 2. Downes, A. and T.P. Blount. 1877. “Research on the effect of light upon bacteria and other organisms.” Proceedings of the Royal Society of London 26:488 – 500. 3. The Nobel Foundation. http://tinyurl.com/6m8u7p (or http:// nobelprize.org/nobel_prizes/medicine/laureates/1903/finsen-bio.html) (accessed June 17, 2008). 4. Hart, J.D. 1936. “Sterilization of air in operating room by special bactericidal radiant energy.” Journal of Thoracic Surgery 6:45 – 81. 5. Wells, W.F., M.W. Wells and T.S. Wilder. 1942. “The environmental control of epidemic contagion. I: An epidemiologic study of radiant disinfection of air in day schools.” American Journal of Hygiene 35:97 – 121. 6. Riley, R.L. and F. O’Grady. 1961. Airborne Infection: Transmission and Control. New York: Macmillan. 7. Menzies, D., et al. 2003. “Effect of ultraviolet germicidal lights installed in office ventilation systems on workers’ health and wellbeing: double-blind multiple crossover trial.” The Lancet 362:1785 – 1791. 8. U.S. General Services Administration. 2005. PBS-P100, Facilities Standards for the Public Buildings Service. 9. U.S. Department of Health and Human Services/Centers for Disease Control and Prevention. 2005. “Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings, 2005.” Morbidity and Mortality Weekly Report 54(RR-17). 10. U.S. Department of Homeland Security/Federal Emergency Management Agency. 2003. FEMA 426, Reference Manual to Mitigate Potential Terrorist Attacks Against Buildings. 11. U.S. Environmental Protection Agency. 2007. EPA 600/R-07/157, Building Retrofits for Increased Protection Against Airborne Chemical and Biological Releases. 12. Collins, F.M. 1971. “Relative susceptibility of acid-fast and non-acid-fast bacteria to ultraviolet light.” Applied Microbiology 21:411 – 413. 13. General Electric Engineering Division, Lamp Department. 1950. “Bulletin LD-11, Ultraviolet Air Sanitation.” 14. Philips Lighting Division. 1985. Germicidal Lamps and Applications. 15. Kowalski, W.J. and W.P. Bahnfleth. 2000. “Effective UVGI system design through improved modeling.” ASHRAE Transactions 106(2):4 – 15. 16. Riley, R.L. and E.A. Nardell. 1989. “Clearing the air: the theory and application of ultraviolet disinfection.” American Review of Respiratory Disease 139:1286 – 1294. 17. Xu, P., et al. 2003. “Efficacy of ultraviolet germicidal irradiation of upper-room air in inactivating airborne bacterial spores and mycobacteria in full-scale studies.” Atmospheric Environment 37:405 – 419. 18. Peccia, J., H.M. Werth, S. Miller and M. Hernandez. 2001. “Effect of relative humidity on the ultraviolet induced inactivation of airborne bacteria.” Aerosol Science and Technology 35:728 – 740. 19. Air Conditioning and Refrigeration Technology Institute. 2002. “Report ARTI-21CR/610-40030-01, Defining the Effectiveness of UV Lamps Installed in Circulating Ductwork.” 20. Lau, J., W. Bahnfleth and J. Freihaut. 2007. “Predicted performance of in-duct UVGI systems under variable operating conditions.” Proceedings of IAQ 2007—Healthy and Sustainable Buildings. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. ashrae.org August 2008 In-duct systems benefit from increasing UVC reflectivity within the ductwork. Reflection can be an economical way to increase UVGI intensity because reflected energy adds to direct energy in determining UV dose. While a surface may reflect visible light, it may not reflect UVC energy. For instance, polished brass reflects most visible light, but less than 10% of UVC. Galvanized duct material has a UVC reflectivity of around 55%. Aluminum and other reflective materials may be used to line ducts to improve effective irradiation levels. System designers and manufacturers can provide information on improving reflectivity for UVGI in-duct applications. Although reflectivity is desirable for in-duct systems, it could be a safety concern with upper-air systems. Properly designed upper-air fixtures virtually eliminate UV reflections from ceilings or opposing walls located more than 10 ft (3 m) from the outward opening of the fixture. Yet, there may be times when fixtures must be mounted in suboptimal positions. Reflections from walls and ceilings can be minimized with low UV-reflectance paint or wall coverings while maintaining adequate irradiation in the upper air and limiting UV exposure to people in the room. UV Degradation Inorganic materials like metal and glass are not affected by normal exposure to UVC energy, but organic materials can rapidly degrade. Organic materials, such as synthetic filter media, gaskets, rubber, motor windings, electrical insulation, internal duct insulation, and plastic piping, within 6 ft (1.8 m) of in-duct lamps should be shielded with UV-resistant materials. Failure to shield these materials can lead to damaged system components resulting in reduced performance and/or safety concerns. Degradation of system components is usually not a concern with upper-air systems. Building materials can degrade if wall or ceiling paint is cracked or peeling. Books, paper, and other items stored in the upper-portion of a room may suffer from discoloration and deterioration. Plants being wilted by upper-air UVGI systems have also been reported. While not desirable, these problems can be prevented easily by proper maintenance and by locating susceptible items outside the irradiated zone. Conclusions Although support for the technology is growing, the industry still lacks design guidance applicable to all UVGI systems and standards for testing the effectiveness of individual devices and complete systems. Until this information becomes available, systems should be sized and designed using the best available information, which has been briefly summarized here. More detailed information can be found in the new chapter on UVGI technologies published for the first time in the 2008 ASHRAE Handbook—HVAC Systems and Equipment. Similar UVGI chapters will be added to the other ASHRAE Handbook volumes during subsequent revisions. 36 ASHRAE Journal http://tinyurl.com/6m8u7p http://nobelprize.org/nobel_prizes/medicine/laureates/1903/finsen-bio.html http://nobelprize.org/nobel_prizes/medicine/laureates/1903/finsen-bio.html http://ashrae.org

Table of Contents Feed for the Digital Edition of ASHRAE Journal - August 2008

ASHRAE Journal - August 2008 Contents Commentary Industry News Letters Meetings and Shows Maintain to Sustain—Delivering ASHRAE’s Sustainability Promise Ultraviolet Germicidal Irradiation: Current Best Practices Improving Humidity Control With Energy Recovery Ventilation Single- or Two-Stage Compression Data Center Cooling: Using Wet-Bulb Economizers Building Sciences InfoCenter Practical Pointers Products Emerging Technologies Washington Report People Special Products Classified Advertising Advertising Index

ASHRAE Journal - August 2008

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