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BACKDRAFT
DAMPER:
Damper
used
in
a
system
to
relieve
air
pressure
in
one
direction
and
to
prevent
airflow
in
the
opposite
direction.
BACT
(BEST
AVAILABLE
CONTROL
TECHNOLOGY):
An
emission
limitation
based
on
the
maximum
degree
of
emission
reduction
achievable
under
Title
1
of
the
CAAA.
EPA
will
establish
BACT
standards
for
serious,
severe
and
extreme
nonattainment
areas.
BAG:
The
customary
form
of
filter
element.
Also
known
as
tube,
stocking,
etc.
Can
be
unsupported
(dust
on
inside)
or
used
on
the
outside
of
a
grid
(cage)
support
(dust
on
outside).
BAGHOUSE:
An
air
pollution
abatement
device
that
traps
gas-borne
particulates
by
forcing
the
gas
through
filter
bags.
BALANCING:
(1)
On
a
fan,
the
process
of
adding
(or
removing)
weight
on
a
rotor
to
move
the
center
of
gravity
toward
the
axis
of
rotation.
(2)
In
a
ventilation
system,
it’s
the
process
of
measuring
or
calculating
the
airflow
at
a
branch
and
altering
duct
size
or
a
valve
to
attain
desired
airflow
at
that
branch.
BAROMETRIC
PRESSURE:
A
measurement
of
the
pressure
of
the
atmosphere;
standard
is
29.92”
Hg.
BI
FAN:
Centrifugal
fan
with
backward
inclined
blades
that
move
air
more
efficiently
than
straight
blade
fans.
BI
fans
are
usually
on
the
clean
side
of
a
piece
of
control
equipment
as
the
blades
are
not
especially
abrasion
resistant.
BIO-HEPA
FILTER:
High-efficiency
media
air
filter
designed
to
be
95%
efficient
on
0.3
micron
and
larger
particles
when
clean.
BLAST
AREA:
The
fan
outlet
area
less
the
projected
area
of
the
cut-off.
BLAST
GATE:
Sliding
damper
in
a
duct
used
to
balance
airflow
or
to
isolate
a
process
from
a
system.
BLEED:
Particles
of
dust
or
fumes
that
are
able
to
leak
through
filter
media.
BLIND
(BLINDING):
The
blockage
of
filtration
media
by
dust,
fume
or
liquid
covering
the
filter
media
and
not
being
discharged
by
the
cleaning
mechanism.
Once
enough
material
has
built
up,
airflow
is
severely
restricted
and
the
elements
have
to
be
cleaned
or
replaced.
BLOW-PIPE:
See
manifold.
BLUE
SMOKE:
A
descriptive
term
for
the
gaseous
hydrocarbons
that
escape
from
hot
asphalt
and
other
sources
of
VOC.
BRAKE
HORSEPOWER:
The
horsepower
actually
required
to
drive
a
fan.
This
includes
the
energy
losses
in
the
fan
and
can
be
determined
only
by
actual
tests
of
the
fan
(this
does
not
include
the
drive
losses
between
motor
and
fan).
BRANCH
DUCT:
Duct
used
to
transport
contaminants
from
a
collection
point
to
a
main
duct
or
air
cleaner.
BRIDGE:
Material
building
across
an
opening
(such
as
a
screw
conveyor)
and
blocking
off
that
opening.
BRITISH
THERMAL
UNIT
(BTU):
Heat
required
to
raise
the
temperature
of
1
lb.
of
water
by
1°
F.
The
BTU/hr.
required
to
raise
the
temperature
of
a
volume
of
standard
air
by
a
specific
number
of
degrees
is
calculated
by
the
formula:
Btu/hr
=
Temp.
Rise
x
CFM
x
1.085
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