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UV dosage required for destruction of microorganisms

UV dosage is a function of the intensity of the UV light, and the amount of time the microorganisms are exposed to that light (referred to as Residence Time). The limitation of most UV systems is that there is rarely enough UV dosage created to destroy airborne bacteria or viruses, and the lamps are not located in effective areas, usually located at the system‘s exhaust (after the HEPA).

TRACS is designed to address both of these concerns. First, three lamps are mounted in a highly reflective kill chamber that amplifies the UV radiation to a level to make it effective against most airborne pathogens. The UV dosage in TRACS is 18,415 microwatt sec/cm2, allowing it to destroy smaller bacteria and viruses. However, even hospital UV systems rarely create enough UV dosage to destroy large airborne molds, spores, and some bacteria because their size requires a very high UV dosage for complete destruction. Fortunately, such microorganisms can be easily trapped by the HEPA filter. However, this can present a problem in non-UV systems and units having the UV located at the exhaust.

While HEPA filters have been the standard for high risk infection control in hospitals and laboratories (because they have been proven to remove airborne microorganisms), they require at least annual replacement due to biological contamination. As microorganisms collect on the HEPA filter over a long period of time, there is a risk of bacteria and mold growth on the HEPA filter as trapped bacteria/mold live, grow, and feed on each other and trapped dust, etc... (Especially in warm and humid environments). This is sometimes called "bacterial grow-through" whereby microorganisms can live and breed on the HEPA media, eventually even eating through the media. This ruins the integrity of the HEPA filter and possibly creates even more contamination within the room as the microorganisms/ mold is dispersed by the air cleaner.

However, by having the UV lamps located before and continually bathing the dirty side of the HEPA filter, the bacteria and mold collected are destroyed and deactivated over time. This is because an infinite residence time is produced, as the trapped bacteria/mold is exposed to the UV light as long as the unit remains on. In all, the UV in TRACS not only destroys airborne bacteria and disease, but it also continually radiates the dirty side of the HEPA filter to extend HEPA filter life and ensure the destruction of larger more difficult microorganisms.

Molds Dosage micro-watt sec/cm2
ASPERGILLUS AMSTELODAMI 77,000
ASPERGILLUS FLAVUS 99,000
ASPERGILLUS GLAUCUS 88,000
ASPERGILLUS NIGER (BREAD MOLD) 330,000
MUCOR RACEMOSUS 35,200
OOSPORA LACTIS 11,000
PENICILLIUM CHRYSOGENUM 56,000
PENICILLIUM DIGITATUM 88,000
PENICILLIUM EXPANSUM 22,000
RHIZOPUS NIGRICANS (CHEESE MOLD) 220,000
BACTERIA  
BACILLUS ANTHRACIS SPORES 46,200
BACILLUS SUBTILIS SPORES 22,000
CLOSTRIDIUM TETANI 23,100
CORYNEBACTERIUM DIPPTHERIAE 6,500
DYSENTERY BACILLI 4,200
ESCHERICHIA COLI 6,600
LEGIONELLA PNEUMOPHILA 2,760
(LEGIONNAIRES DISEASE)  
INFECTIOUS JAUNDICE 6,000
MYCOBATERIUM TUBERCULOSIS 10,000
RHODOSPIRILLUM RUBRUM 6,100
SALMONELLA ENTERITIDIS 10,000
SALMONELLA TYPHOSA (TYPHOID) 26,400
SALMONELLA 6,160
SHIGELLA DYSENTERIAE (DYSENTERY) 3,400
STAPHLYLOCOCCUS AUERUS 6,600
STREPTOCOCCUS PYROGENES 4,200
STREPTOCOCCUS SALIVARIUS 4,200
VIRUSES  
INFECTIOUS HEPATITIS 8,000
INFLUENZA 3,400
YEASTS  
SACCHAROMYCES CEREISIAE 13,200
SACCHAROMYCES ELLIPSOIDEUS 13,200