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UV-C Lamps - A Short(wave) History
When people first see the futuristic blue hue of an ultravioet-c (UV-C) lamp, some might think ultraviolet germicidal irradiation (UVGI) is a recent invention.
Yet, knowledge of UV-C goes back well over 100 years, having gone through various phases of development.
Here’s a brief history outlining some pivotal points in the century-long history of the various applications of UV-C.
Like electricity, ultraviolet light is as old as the universe. It just took someone to notice. In 1877, British Physiologist Arthur Downes and scientist Thomas P. Blunt noticed. They put solution-filled test tubes outside and discovered that sunlight could kill and inhibit the development of pathogenic bacteria.
Some 25 years later, the German Ophthalmologist Ernst Hertel built on this knowledge, determining that light in the UV-C wavelength, rather than UV-A or UV-B, is the most effective for killing microorganisms. Around the same time, the Danish Professor Niels Finsen won the Nobel Prize for Physiology in recognition of his work in treating lupus vulgaris bacteria on human skin with concentrated light (See image).
In the 1930s and 1940s, William F. Wells, a Harvard University sanitary engineer, made a significant stride in the knowledge and application of UV-C light for disinfection by proving its effectiveness in killing airborne microorganisms. It was Wells who discovered that bacteria and viruses can be transmitted to people through the air they breathe.
He applied this knowledge by installing upper-room UV lamps in suburban Philadelphia day schools to combat the spread of measles and compared infection rates to schools without UV-C. The schools without UV-C saw a 53.6 percent infection rate, while the schools with the lamps saw a 13.3 percent infection rate.[i]
Around the same time, in 1936, Dr. Deryl Hart experimented with UV-C to disinfect an operating room at Duke University Hospital. He reported an 11.38 percent reduction in the rate of postoperative infection rates.[ii]
Throughout the next few decades, UV-C was applied in schools and hospitals across the country, proving its ability to inactivate microorganisms and bacteria.
Over the next few decades, the scientific community’s understanding of UV-C and its impact on microorganisms continued to broaden. In various studies, UV-C was shown to be effective in inactivating E. coli and tuberculosis.[iii]
Around this time, the earliest applications of UV-C in HVAC/R systems appeared, although champions of the technology struggled to reproduce the success of Wells in preventing the airborne spread of measles[iv],[v],[vi],[vii]. This delay slowed the enthusiasm around UVGI, which waned further as Americans embraced a new infection-control panacea in the late 1950s: antibiotics.
Society’s increasing faith in antibiotics and other advanced cleaning agents slowed the development of UV-C technology until the 1970s and 1980s when it was learned that germs were evolving resistances. This rise in drug-resistant “superbugs” and hospital-acquired infections sparked a renewed interest in UV-C, which can kill virtually any microorganism.
The stage was set for UV-C’s revival. In 1995, Forrest Fencl, a co-founder of UV Resources, was among those responsible for the resurgence of UVGI in HVAC/R equipment. Specifically, Fencl’s work around coil irradiation led to optimized UV-C effectiveness in the hostile cold and fast-moving air streams of HVAC/R systems.
Today, there are three primary means of applying UV-C systems against infectious agents: upper-air (upper-room), coil irradiation and airstream disinfection. Upper air/room systems are installed in spaces, such as above patient beds and in waiting rooms, corridors and break areas in facilities ranging from schools, to hospitals, to international airports. Coil-irradiation and air-stream-disinfection systems are installed within air-handling units and duct runs.
UV-C is now an accepted and respected solution for any application looking to improve IAQ and/or HVAC system efficiency. Its benefits have even been touted by ASHRAE. Expect the future of UV-C to be just as eventful as its past.
[i] (Reed 2010). "The History of Ultraviolet Germicidal Irradiation for Air Disinfection." Public Health Reports Vol. 125: 16-24.
[iv] Wells MW. Ventilation in the spread of chickenpox and measles within school rooms. JAMA. 1945;129:197–200.
[v] Perkins JE, Bahlke AM, Silverman HF. Effect of ultra-violet irradiation of classrooms on spread of measles in large rural central schools: preliminary report. Am J Public Health Nations Health. 1947;37:529–37. [PMC free article] [PubMed]
[vi] Wells MW, Holla WA. Ventilation in the flow of measles and chickenpox through a community: progress report, Jan. 1, 1946 to June 15, 1949, Airborne Infection Study, Westchester County Department of Health. JAMA. 1950;142:1337–44. [PubMed]