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ABATEMENT:
The
reduction
of
pollutant
discharge
by
means
of
process
modification,
shutdown
or
addition
of
control
equipment.
ABRASIVE
DUST:
Coarse
particles
such
as
sand,
metallic
compounds,
ceramic
and
glass,
that
can
cause
rapid
wear
on
ductwork,
air
cleaners
and
fans.
ABSORBER:
A
kind
of
scrubber
utilizing
the
absorption
principle.
ACCELERATION
LOSS:
The
velocity
pressure
required
to
accelerate
the
air
from
rest
to
the
duct
velocity
or
slot
velocity,
whichever
is
higher.
ACFM:
Actual
Cubic
Feet
per
Minute
of
gas
volume
at
the
actual
conditions
of
temperature,
pressure,
moisture,
elevation
and
gas
composition.
See
gas
flow
rate.
ACGIH:
The
American
Conference
of
Governmental
Industrial
Hygienists
is
a
professional
society
devoted
to
the
development
of
administrative
and
technical
aspects
of
worker
health
protection.
Membership
is
limited
to
professional
personnel
in
governmental
agencies
or
educational
institutions
engaged
in
occupational
safety
and
health
problems.
The
ACGIH
issues
guidelines
and
recommendations
in
the
form
of
Threshold
Limit
Values
(TLVs)
which
are
published
annually.
ACRYLIC:
A
synthetic
polyermized
fiber
that
contains
at
least
85%
acrylonitrile.
ACRYLONITRILE:
A
colorless,
volatile,
flammable
liquid
nitrile
C3H3N
used
chiefly
in
organic
synthesis
and
for
polymerization.
ADSORBENT:
In
addition
to
the
adjectival
meaning,
the
term
describes
any
of
several
substances
that
collect
gaseous
pollutants.
Used
both
for
measurement
and
control.
ADSORPTION:
The
adhesion
of
a
substance
to
the
surface
of
a
solid
or
liquid.
AEROSOL:
Particulate
matter
solid
or
liquid,
typically
under
1
micron,
suspended
in
the
air.
Particles
are
sometimes
classified
as
dust,
fog,
fume,
mist
or
smoke.
In
general,
the
term
aerosol
refers
to
particles
that
remain
suspended
in
the
air
for
an
extended
period
of
time.
AF:
Fan
wheel
design
with
airfoil-shaped
blades.
AGGLOMERATING
DUST:
Dust
particles
that
exhibit
tendencies
for
particle
growth,
such
as
powdered
milk,
fertilizer,
detergents,
etc.
AIR
CHANGES
PER
HOUR
(ACH):
The
movement
of
a
volume
of
air
in
a
given
period
of
time.
If
a
building
has
one
air
change
per
hour,
it
means
that
all
of
the
air
in
the
building
will
be
replaced
in
a
one-hour
period.
AIR
CLEANER:
A
device
designed
for
collecting
airborne
impurities,
such
as
dusts,
gases,
fumes
and
smokes.
AIR
CONDITIONING:
Treating
air
to
meet
the
requirements
of
a
conditioned
space
by
controlling
its
temperature,
humidity,
cleanliness
and
distribution.
AIR
CONTAMINANT:
An
impurity
emitted
to
the
outside
air.
It
can
be
solid,
(dust,
particulate
matter),
liquid
(vapor,
mist)
or
gas
(carbon
monoxide,
sulfur
dioxide).
AIR
CURTAIN:
Mechanical
air-moving
device
designed
to
limit
the
in-flux
of
unwanted
air
at
a
building
opening.
AIR
FILTER:
An
air
cleaning
device
which
removes
contaminants
from
an
airstream.
AIR
HANDLING
UNIT:
Factory-made
encased
assembly
consisting
of
a
fan
or
fans
and
other
equipment
to
circulate,
clean,
heat,
cool,
humidify,
dehumidify
or
mix
air.
AIR
LEAKAGE:
Unwanted
air
intruding
into
an
exhaust
system
(holes
in
ducts,
missing
and
ineffective
seals,
etc.).
AIRLOCK:
Term
generally
applied
to
a
rotary
vane
valve
that
keeps
air
from
entering
a
dust
collector,
yet
allows
collected
particulate
to
continuously
discharge
from
the
device.
AIR
MONITORING:
The
continuous
sampling
for
and
measuring
of
pollutants
present
in
the
atmosphere.
AIR
QUALITY
STANDARDS:
The
approximate
concentration
level
of
a
selected
pollutant
that
is
permitted
in
the
atmosphere
to
minimize
detrimental
effects.
AIR
POLLUTION:
The
presence
in
the
atmosphere
of
gases,
fumes
or
particulate
matter
alone
or
in
combination
with
each
other,
in
sufficient
concentration
to
disturb
the
ecological
balance;
cause
objectionable
effects,
especially
sensory
offenses;
cause
transient
or
chronic
illnesses;
or
impair
or
destroy
property.
AIR,
STANDARD:
Dry
air
at
70°
F
and
29.92
inches
Hg
barometric
and
is
approximately
equivalent
to
0.075
lb/ft3.
AIR-TO-MEDIA
RATIO:
The
ratio
of
air
volume
(ACFM)
to
square
feet
of
effective
filter
media
area.
Also
referred
to
as
the
apparent
or
face
velocity
through
the
media
(FPM).
Typically
3
to
20
fpm
for
bag
medias
and
0.5
to
6
fpm
for
pleated-type
media.
AIR
TOXICS:
Any
air
pollutant
for
which
a
national
ambient
air
quality
standard
(NAAQS)
does
not
exist
(i.e.,
excluding
ozone,
carbon
monoxide,
PM-10,
sulfur
dioxide,
nitrogen
oxides)
that
may
reasonably
be
anticipated
to
cause
cancer,
developmental
effects,
reproductive
dysfunctions,
neurological
disorders,
heritable
gene
mutations
or
other
serious
or
irreversible
chronic
or
acute
health
effects
in
humans.
AIR
VELOCITY:
Rate
of
speed
of
an
airstream,
expressed
in
fpm.
ALTITUDE:
The
height
above
sea
level
of
a
given
location.
Density
corrections
for
altitude
are
made
using
the
following
formula,
where
Z
is
the
feet
above
sea
level.
Density
(Alt)
=
Density
(Std)
x
[1
–
(6.73
x
10-6)
Z]5.258
AMBIENT:
Immediate
surroundings
or
vicinity.
AMCA:
Air
Movement
and
Control
Association.
ANEMOMETER:
A
device
that
reads
air
velocity
such
as
a
wind
vane.
In
fan
applications,
it
is
usually
a
spinning-vane-type
instrument
used
to
read
low
velocities
at
registers
and
grills.
ANSI:
American
National
Standards
Institute.
AQUA-SURGER:
UAS’
proprietary,
in-place
cleaning
system
associated
with
SMOG-HOG
electrostatic
precipitators.
Consists
of
fixed
face
and
overhead
cleaning
nozzles
and
associated
detergent
injection
equipment.
ARI:
Air
Conditioning
and
Refrigeration
Institute.
AREA
SOURCE:
Any
small
source
of
non-natural
air
pollution
that
is
not
large
enough
to
be
classified
as
a
major
source
or
point
source.
AROMATICS:
A
type
of
hydrocarbon,
such
as
benzene
or
toluene,
added
to
gasoline
to
increase
octane.
Some
aromatics
are
toxic.
ASHRAE:
American
Society
of
Heating,
Refrigeration
and
Air
Conditioning
Engineers.
ASME:
American
Society
of
Mechanical
Engineers.
ASPECT
RATIO:
The
ratio
of
the
width
to
the
length.
AR
=
W/L
ASTM:
American
Society
of
Testing
Materials.
ATMOSPHERIC
PRESSURE:
One
atmosphere
is
approximately
14.7
PSI;
407”
water
gauge.
Airflow
is
the
result
of
a
difference
in
pressure
(above
or
below
atmospheric)
between
two
points.
ATTAINMENT
AREA:
An
area
considered
to
have
air
quality
as
good
as
or
better
than
the
National
Ambient
Air
Quality
Standards
as
defined
by
the
Clean
Air
Act.
An
area
may
an
attainment
area
for
one
pollutant
and
a
non-attainment
area
for
another
pollutant.
ATTRITION:
Wearing
or
grinding
down
by
friction.
One
of
the
three
basic
contributing
processes
of
air
pollution;
the
others
being
vaporization
and
combustion.
AXIAL
FAN:
Fan
where
the
airflow
through
the
impeller
is
predominantly
parallel
to
axis
of
rotation.
The
impeller
is
contained
in
a
cylindrical
housing.
AXIAL
FLOW:
In-line
air
movement
parallel
to
the
fan
or
motor
shaft.
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