Basics of UVC

American Ultraviolet Company UVC equipment for HVAC applications works on the same general principle as all UVC sterilization applications: direct exposure to 254nm UVC radiation, given appropriate exposure time, will inactivate the DNA and RNA of microorganisms (such as bacteria, viruses, mold spores, yeast, and protozoa), rendering them “sterile” (unable to reproduce), which, in biological terms, results in a “dead” microorganism.

An acceptable kill rate is determined by the total amount of UVC energy a microorganism “sees”. This is a “dosage”. Dosage is a product of the intensity of UVC radiation (expressed in microwatts per square centimeter) and exposure time to that radiation. You can find the necessary dosage for most common mold spores in the below Table. Mold spores are generally much more difficult to kill than microorganisms and viruses and, thus, require a much higher dosage of UV. The values shown under the percentage kill are in microwatts per square centimeter of UVC energy.

MOLD SPORES	Color	90%	100%
Aspergillius flavis	Yellowish green	60,000	99,000
Aspergillius glaucus	Bluish green	44,000	88,000
Aspergillius niger	Black	132,000	330,000
Mucor racemosus A	White gray	17,000	352,000
Mucor racemosus B	White gray	17,000	352,000
Oospora lactis	White	5,000	11,000
Penicillium expansum	Olive	3,000	22,000
Penicillium roqueforti	Green	13,000	26,400
Penicillium digitatum	Olive	44,000	88,000
Rhisopus nigricans	Black	111,000	220,000

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