culating
air. There is a
speed
control located
in
the
light
canopy.
Tum
it clockwise
until
you
have
the
desired
airflow. If the airflow
cannot
be
maintained,
it will
be
necessary to replace
the
HEP A filters. (See "Replacing the HEPA
Filters'
later
in
this section.)
.
WARNING!
When
the
light
canopy
is
lowered, some
electrical
parts
are exposed.
Do
not perfonn
,
:his
work
unless
you
are a trained electrician
or.
electronic teclmician; ,
Filter
Media
and
Seal
Leak
Tests
When
preparing
your
cabinet for
use
after
shipment,
and
then
at
prescribed
intervals
throughout
its
working
life,
you
will
need
to
verify
that
the
filters
have
maintained
their
integrity. This
is
done
by probe-testing the filter
faces
and
seals.
The
equipment
you
will
need
includes:
•
An
aerosol
photometer.
The
instmment
should
sample
air at a flow rate of 1 CFM.
• A D.O.!'.
generator
with
Laskin nozzle(s).
Liquid
dioctylphthalate
(D.O.P.),
dioctylsebacate or a
comparable
substance is
aerosolized
by
flowing
through
the nozzle(s).
When
generated
with
Laskin
type
nozzle(s),
the
mean
droplet
size of
the
aerosol is
99
percent
less
than
0.3 microns.
Here
is
the
procedure:
1
..
it
according
to the manufach1rer's
instructions.
2.
Position
the
D,O.P.
generator
so as to
introduce
air
generated srnoke into the area
upstream
of
the filter.
1. 1Vfeasure
the
tlpstrearn
concentration
of
D.O.P.
WARNING!
Do
not
do
this
unless
the
unit
has been
properly decontaminated.
20
4.
Holding
the
photometer
probe
about
one
inch
from the filter face
with
the
diffuser
removed
on
the
downstream
side, scan
the
entire surface area
and
perimeter
(filter
gasket frame area)
in
slightly
overlapping
strokes
at
a traverse rate of
not
more
than
ten
feet
per
minute. Repeat at 90
degrees
to the
first scan pattern.
5.
Eliminate leaks
in
the gasket
frame
area
by
re-tightening the filter gasket.
6.
An
HEPA
filter
i.s
considered acceptable
when
all significant leaks
have
been
sealed.
Airflow
Smoke
Pattern
Test
To check for the direction of air
movement,
use
a
smoke
generator
and
trace along
the
front access
opening
on
the inside of the cabinet.
Observe
that
no
smoke
is escaping from the
work
area.
In
order
to be
sure
that
room
air
is
not
entering
the
work
area, trace along the
outside
of
the
front
access opening. Observe
that
no
smoke
penetrates
farther into the cabinet
than
the
front
perforated
grille.
Cabinet
Integrity
Test
The
purpose
of this test is to
detennine
that
the
cabinet
welds
and
gasketed
seams
are
free of
detectable leaks.
1.
Decontaminate
the
cabinet
if
it
has
been
used.
2.
Seal off the
exhaust
filter
port.
This
may
be
done
by
instal1ing a
gasketed
panel
over
the
opening
using
the
stods
on
the filter
box
flange.
An
alternative is to
tape
a piece
of
cardboard
or plastic over the
opening.
3.
Disconnect the electricity
and
then
remove
the two
nuts
holding the
canopy
clips
at
the
top of the canopy.
Let
the
canopv
pivot
down. Disconi1ect the electrical
plugs
inside
on
e;Kh end. Disconnect the
restraints
and
hlnges.
Lift the
canopy
up
2Lrtd off.
4.
Lm,\.rer
the
vieVv'Screen
untiJ lt is
cornp
ietely
closed.
5.
Remove
the
top viewscreen tracks
by
removing
the tvvo cap
nuts
at
the
top
of
each
track,
then
puJJ.ing
upward
on
each
track.
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