Germicidal ultraviolet radiation is primarily intended for the destruction of bacteria and other microorganisms in the air or on exposed surfaces.  In order for ultraviolet light to kill bacteria, the rays must directly strike the microorganism.  Germs floating in the air or on an outer surface may easily be reached by the ultraviolet rays and, therefore, are readily destroyed.  If the bacteria or mold spores are hidden below the surfaces of a material or are not in the direct path of the rays, they will not be destroyed.

The exposure to ultraviolet necessary to kill bacteria is the product of time and intensity.  High intensities for a short period of time, or low intensities for a long period are fundamentally equal in lethal action on bacteria disregarding the life cycle of the bacteria.

Ultraviolet light will not penetrate most substances.  Meat, cloth and food will not be sterilized by irradiating with ultraviolet because the rays do not go beneath the surface.  Even ordinary glass is opaque to short wave ultraviolet.  Among the very few exceptions to this rule are clear water, which does permit some penetration, certain plastic films and specialty glass.

It has been an accepted practice to consider 0.5 microwatts per square centimeter for an eight-hour exposure and 0.1 microwatt per square centimeter for a twenty-four hour exposure as the allowable maximum intensity of 254nm ultraviolet radiation incident upon people.  These germicidal lights generate considerably more than this, so you must take precautions to shield yourself and others when operating the UV light.

The following technical data is compiled from information published by Philips lighting.  We are not responsible for any errors or miscalculations, although we believe it is correct.

Handheld Germicidal Light - Model FlashUV5