Kewaunee Supreme Air Series, Руководство по эксплуатации и техническому обслуживанию

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VFHOMT-11/18
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24
Recommended Work Practices
(continued)
Maintaining the Protective Air Barrier for a Safe Work Area
(continued)
Large containers or equipment such
as furnaces, incubators and oil baths
often interfere with air flow inside
the fume hood by causing lazy air
and reverse flows which may affect
airflow patterns. Placing large, bulky
equipment on legs will help improve
airflow patterns by allowing air to
circulate beneath the equipment.
(See
Figure 5.)
The fume hood should not be used for
storage of chemicals and apparatus.
Remove all unnecessary containers
and equipment from the hood.
The air velocities used to provide
containment in fume hoods are
relatively low and the air flow patterns
are easily disrupted. Avoid making
rapid movements while working at the
hood or while walking past the hood.
When working at a fume hood, always
open the sash only as far as needed to
access to the work area. The lowered
sash increases the distance
(D in
Figure 6)
between your breathing zone
and the area where contaminants
may escape. In addition the smaller
hood face area makes the hood less
susceptible to room drafts and other
external air disturbances.
The sash also provides protection
by replacing part of the protective
air barrier with a solid barrier
against contaminants and splashing
chemicals.
If the hood has a sash stop to limit
sash travel or is marked for a safe sash
height, the sash should not be raised
above this point while contaminants
are being generated within the hood.
If continuous access is not needed
to the inside of the fume hood, the
sash should be closed completely.
(See Figure 7)
A closed sash provides
protection from flying debris or a
runaway reaction. It also eliminates the
effects of room drafts or other adverse
air currents.
D
D
Figure 5
Effect of large equipment
Figure 6
Effect of lowering the sash
Figure 7
Airflow through By-Pass
with Sash Closed
If your hood has horizontal sashes,
be sure they are all in place when
working with contaminants inside the
hood. Operating the hood with any
of the sashes removed reduces the
protection they provide by decreasing
the velocity of the air entering the hood
face. If you remove any hood sashes
while setting up equipment, be sure
to replace them before beginning the
actual procedure. On hoods with a
combination vertical/horizontal sash,
the hood should be operated either
with the vertical frame closed while
the horizontal panels are open or the
horizontal panels closed while the
vertical frame is open.