NuAire LabGard NU-560-400, Operation & Maintenance Manual

Page: 92 / 103

OM0295
Rev 2 September 2020 Page 92 of 103
10.0 Optional Equipment
10.1 Ultraviolet Light
Ultraviolet light will injure your eyes. Avoid direct viewing at all times.
Personnel should not be present when ultraviolet lamp is on
10.1.1 Overview
The germicidal ultraviolet is primarily intended for the destruction of bacteria and other microorganisms in the air
or on directly exposed surfaces. Approximately 95% of the ultraviolet radiations from germicidal tubes are in the
253.7 nanometer region. This is a region in the ultraviolet spectrum which is near the peak of germicidal
effectiveness. The exposure necessary to kill bacteria is the product of time and intensity. High intensities for a
short period of time, or low intensities for a longer period are fundamentally equal in lethal dosage on bacteria
(disregarding the life cycle of bacteria). The intensity of light falling on a given area is governed by the inverse law;
that is the killing intensity decreases as the distance increases from the tube.
The germicidal tube is placed in the cabinet to provide an average intensity of 100 microwatts per square
centimeter (for a new tube) falling on a horizontal plane defined by the center of the work surface. The
minimum requirement per paragraph 5.12 of NSF Standard 49 is 40 microwatts per square centimeter (ref. NSF
Std. #49, June, 1976).
Since ultraviolet rays will not penetrate ordinary glass, it is recommended that the sliding window be closed while
the ultraviolet light is on within the cabinet; or that personnel leave the cabinet face area.
10.1.2 Operation
The operation of the ultraviolet light is accomplished by closing the sliding window and pressing the UV switch
location on the front panel. The sliding window is interlocked to the ultraviolet light so, when the sliding window is
raised, the ultraviolet light will turn off.
10.1.3 Precaution
The rays from germicidal tubes may cause a painful but temporary irritation of the eyes and reddening of the skin,
if of sufficiently high intensity, or if exposure covers a prolonged period of time. For this reason, one should avoid
direct eye and skin exposure to ultraviolet light. If exposure cannot be avoided, it is necessary for personnel to
wear eye goggles or face shields, and long sleeve gowns with rubber gloves.
Since ultraviolet rays will not penetrate ordinary glass, it is recommended that the sliding window be closed while
the ultraviolet light is on within the cabinet; or that personnel leave the cabinet face area.
10.1.4 Maintenance
The output of an ultraviolet light deteriorates with burning age. The useful life of the light is approximately 7000
hours under specific test conditions.
NOTE: Before testing with lamp off, the light may be cleaned with a lint-free cloth dampened with alcohol or
ammonia and water.
It is recommended that either a time schedule be established or the tube's output be measured periodically and
the tube replaced when its output falls below 40 microwatts per square centimeter or exceeds 7000 hours of
operation. Lights should be allowed to operate approximately 5 to 10 minutes (longer when the light is in low
temperatures) to warm up sufficiently before reading the output with a meter.
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CAUTION
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