4: Performance Features and Safety Precautions
28
Cabinet Grilles, Ductwork and Air Balance Controls
The location, size, and pattern of the grilles at the front and rear of the work area
affect cabinet containment and performance.
Note: Do not block or obstruct the grilles of the cabinet.
The internal ductwork of the cabinet conveys the air from the work area to the
blower, and then from the blower to the filters. The positive pressure rigid plenum
of the cabinet is designed to deliver a more uniform airflow to both HEPA filters,
optimizing filter loading and operational life.
Ultraviolet (UV) Lamp
The optional UV lamp generates a primary wavelength of light of 254nm. A
secondary emission is in the visible (blue) wavelength, resulting in the
characteristic blue color while operating. UV light at this wavelength is biocidal,
primarily by creating thymine dimers in DNA. These dimers prevent the correct
transcription of the DNA into RNA, resulting in cellular death or viral inactivation. In
order to be effective, the UV light must directly strike the nucleic acid, and its
effectiveness can be diminished or negated by dissolved proteins or metals, or by
other UV-opaque substances protecting the target nucleic acid.
Because of its limitations, UV light should be used as an adjunct to good surface
disinfection practices. In order to get optimum performance from the UV light, it
should be replaced after 6,000 hours of operation or less, and the exterior surface
of the lamp should be kept clean and free of dust.
Note: The cabinet records the number of hours of operation of the UV light. You
can program in the number of hours (in 100-hour increments) it will operate before
a replacement message is displayed.
Note: UV irradiation is absorbed by the tempered safety glass of the sash.
Independent research has shown that the level of UV irradiation on the outside of
the cabinet’s sash is equal to background radiation levels.
Note: The UV sensitivity of a target organism varies, depending on the UV output
of the lamp, the genus and species of the organism, the medium the agent is
suspended in, etc. Contact the Health and Safety Officer at your facility for UV light
use and recommendations.
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