also
provide
lab
personnel
with
a
physical
barrier
to
chemicals
and
their
reactions.
Fume
hoods
are
evaluated
 each
to
verify
their
proper
operation.
They
are
generally
set
back
against
the
walls
to
cover
up
the
exhaust
 ductwork.
Because
of
their
shape,
they
are
generally
dim
inside
but
have
a
provision
for
a
light
source.
the
 front
opening
is
made
up
of
glass,
able
to
move
up
and
down
on
a
counter
balance
mechanism.