Microorganism growth can also increase airflow resistance and reduce heat transfer, lowering the capacity and energy efficiency of the cooling system. Manually cleaning the coils is a laborious process that only temporarily removes the contaminants.
Using ultraviolet germicidal irradiation, produced by lamps designed specifically for this purpose, can provide continuous, cost-effective coil cleaning. These lamps are designed to emit radiation in the wavelength of 253.7 nanometers (nm) to provide the greatest disinfection ability. (The range spectrum of 200 to 280 nm is the "C" range of ultraviolet radiation, hence the term UVC.) This radiation is absorbed by the DNA molecule of the microorganism, producing mutation, and eventually, deactivation. Thinner-walled viruses are most readily deactivated, followed by bacteria and then fungi.