Lethal light

May 2, 2007
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Air conditioners and potato tumblers are being engineered to deliver a dose of short-wave ultraviolet light to control mold, viruses and bacteria that infect food.

Robert S. Scheir, president and chairman, Steril-Aire Inc., Burbank, CA

From radio signals to gamma waves, the electromagnetic spectrum offers considerable potential to prepare and preserve food products. Knowing precisely which wavelength in the spectrum to apply to a particular need is only the first step, however: scientists and engineers also need to fabricate systems that can withstand the rigors of an industrial environment. The application of UVC, short-wave ultraviolet in the C band range (200 to 280 nanometers) to inactivate mold, bacteria, fungus, viruses and other spoilage organisms illustrates the development challenge.

UV lamps to treat germicidal disease date to the 19th Century, when Nobel laureate Niels Ryberg Finsen used UV to treat skin infections in treatments that presaged today’s chemotherapy. After the 1976 Legionnaire’s Disease outbreak in a Philadelphia hotel, medical science linked Legionella bacteria to heating, ventilating and air conditioning (HVAC) systems that can spread bacteria and viruses thriving in warm, moist environments. Among the scientists who worked on a solution was Brad C. Hollander, who developed a UVC lamp to improve indoor air quality. Hollander was issued a patent in 1994 for an electric discharge device to sterilize HVAC air, and the following year Steril-Aire Inc. was established to commercialize the technology. The company now is based in Burbank, CA, and is headed by Robert S. Scheir, president and chairman. 

In one of the 10 US patents assigned to Steril-Aire, Scheir cites a study involving a 20-year-old HVAC system in City of Industry, CA. Biocides, high-pressure sprayers and other treatments provided temporary removal of mold and bacteria from the cooling coils, but buildup resumed in as few as three days. The inventor configured germicidal lamps to permanently resolve microbial encrustation on the coils and boost heat transfer efficiency up to 30 percent, improving airflow and energy efficiency by a similar amount.

Scheir holds a PhD in medical microbiology from UCLA and performed graduate studies in immunochemistry at the School of Hygiene and Public Health at Johns Hopkins University. Before joining Steril-Aire, he was a senior scientist at McDonald-Douglas Corp., specializing in biological-warfare detection instrumentation.

An array of short-wave UV lamps provides a kill step against mold, viruses and bacteria in this tumbling drum bound for duty in a potato processing plant. Source: Steril-Aire Inc.

FE: How do your lamps differ from a bug zapper?

Scheir: Bug lights mounted on a wall emit UV waves that are close to 400 nanometers. The light attracts flying insects, which fly to the light source and are electrocuted.

UVC from vaporized mercury lamps emit waves of 253.7 nanometers, which is close to 265, the wavelength that destroys DNA and provides maximum germicidal effectiveness. Altering the DNA prevents replication and causes cell death. Effectiveness of UVC is directly related to time and intensity. The intensity 2 inches from the lamp is almost three times greater than at 6 inches, and at 12 inches intensity is half the level at 6 inches. Total irradiation also is impacted by reflectance within the cavity. With aluminum and aluminized materials, you get about 85 percent bounce off the surface, potentially increasing the dosage received by organisms.

FE: What does your firm manufacture?

Scheir: We have developed system-engineered UVC emitters that, unlike conventional UVC lamps, work in cold environments. Standard UVC lamps lose output to the point they don’t work below 40

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