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MACT
(MAXIMUM
ACHIEVABLE
CONTROL
TECHNOLOGY):
The
standard
to
which
sources
of
HAPs
will
have
to
comply.
The
CAAA
defines
MACT
as
“the
maximum
degree
of
reduction
in
emissions…achievable
for
new
or
existing
sources…taking
into
account
the
cost
of
achieving
such
reductions.”
MACT
standards
for
existing
sources
must
be
at
least
as
stringent
as
the
average
level
of
control
achieved
at
the
best
controlled
12%
of
facilities,
and
MACT
for
new
sources
will
have
to
be
even
stricter.
MAGNEHELIC®
GAUGE:
Gauge
used
for
measuring
pressure
drop
across
filter
media.
The
gauge
displays
static
pressure
in
inches
of
water.
This
is
a
registered
trademark
of
the
Dwyer
Company.
MAIN
OR
TRUNK
DUCT:
Duct
that
the
branch
ducts
from
multiple
sources
of
contaminant
generation
enter.
The
main
or
trunk
duct
transports
the
contaminated
air
to
the
air
cleaning
or
exhausting
equipment.
MAJOR
SOURCE:
A
stationary
source
that
emits
a
large
amount
of
pollution.
In
nonattainment
areas,
under
Title
I
of
the
CAAA,
a
major
source
is
one
which
emits
more
than
100,
50,
25
or
10
tons
per
year,
depending
on
whether
the
area
is
classified
as
Marginal
or
Moderate,
Serious,
Severe
or
Extreme,
respectively.
For
hazardous
air
pollutants,
under
Title
III
of
the
CAAA,
a
major
source
is
one
which
can
emit
more
than
10
TPY
of
any
one
HAP
or
25
TPY
of
total
HAPs.
MAKE-UP
AIR:
See
Replacement
Air.
MANIFOLD:
As
used
in
conjunction
with
pulse-jet
baghouses,
the
pipe
that
extends
over
the
bags
with
a
hole
over
each
bag.
It
distributes
the
compressed
air
pulse
to
the
bags.
Sometimes
called
a
blow-pipe.
MANOMETER:
A
u-shaped
device
for
measuring
the
static
pressure
at
a
point
relative
to
some
other
point.
This
pressure
difference
causes
water
to
rise
or
fall.
The
difference
in
the
level
of
the
water
columns
is
equivalent
to
the
pressure
differential.
MAXIMUM
CONTINUOUS
RATING:
The
point
at
which
the
fan
is
expected
to
operate.
MECHANICAL
COLLECTOR:
Devices
that
are
functionally
dependent
on
the
laws
of
mechanics
governing
the
motion
of
bodies
in
space.
Can
be
operated
dry
or
wet.
When
operated
wet,
devices
are
generally
called
scrubbers.
Examples
of
mechanical
collectors
are
cyclones,
selling
chambers
and
various
types
of
impingement
collectors.
MEDIUM
PRESSURE
CLEANING
AIR:
Air
at
5
to
10
PSIG
used
for
cleaning
baghouses.
MEGA:
A
prefix
meaning
1
million.
MICRO:
A
prefix
meaning
1/1,000,000
abbreviated
by
the
Greek
letter
Insert.
MICROBAR:
A
unit
of
pressure
equal
to
one-millionth
of
an
atmospheric
pressure;
0.0000146
PSI.
MICROMETER:
See
micron.
MICRON
(µ):
A
unit
of
length
equal
to
one-millionth
of
a
meter.
An
average
human
hair
is
70
microns
in
diameter.
In
general,
particles
down
to
40
microns
can
be
seen
without
the
aid
of
magnification.
MIL:
A
unit
of
measure
equal
to
25
microns
or
one-thousandth
of
an
inch.
MILDEW
RESISTANT
FINISH:
An
organic
or
inorganic
finish
to
repel
the
growth
of
fungi
on
natural
fibers.
MILLI:
A
prefix
meaning
1/1,000.
MINIMUM
DUCT
DESIGN
VELOCITY:
Minimum
air
velocity
required
to
keep
the
particles
in
an
airstream
(duct)
in
suspension,
expressed
in
Feet
Per
Minute
(FPM).
MIST:
Suspended
liquid
droplets
generally
less
than
10
microns,
generated
by
condensation
from
the
gaseous
to
the
liquid
state,
or
by
breaking
up
a
liquid
into
a
dispersed
state,
such
as
by
splashing,
foaming
and
atomizing.
MODACRYLIC:
A
synthetic
fiber
that
contains
less
than
85%
acrylonitrile.
MODELING:
An
investigative
technique
using
computer
mathematical,
or
physical
representation
of
a
system
that
accounts
for
all
or
some
of
its
known
properties.
MOLECULAR
WEIGHT:
The
weight
of
a
molecule
expressed
on
a
scale
in
which
the
carbon
isotope
weighs
exactly
12.0;
represents
the
sum
of
the
weights
of
all
the
atoms
in
a
molecule.
As
air
is
a
gas
mixture,
it
does
not
have
a
true
molecular
weight,
but
an
apparent
molecular
weight
determined
by
the
percentages
of
the
molecular
weights
of
each
gas
in
a
composition.
MOTOR
STARTER:
An
electrical
control
device
used
to
start
a
motor
and
to
protect
the
device
from
current
overload
condition.
A
motor
starter
should
be
selected
to
match
the
operating
voltage
and
horsepower
requirements
of
the
motor.
MPH:
Miles
Per
Hour.
MSDS
(MATERIAL
SAFETY
DATA
SHEET):
Compilation
of
data
and
information
on
individual
hazardous
chemicals
produced
by
the
manufacturers
and
importers
of
that
chemical,
as
required
by
OSHA’s
Hazard
Communication
Standard,
29
CFR
1910.1200.
MULLEN
BURST:
The
pressure
necessary
to
rupture
a
secured
cloth
specimen,
usually
expressed
in
pounds
per
square
inch.
MULTI-FILAMENT
(MULTI-FILL):
A
yarn
composed
of
a
number
of
filaments.
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