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RACM
(REASONABLY
AVAILABLE
CONTROL
MEASURES):
A
broadly
defined
term
referring
to
technologies
and
other
measures
that
can
be
used
to
control
pollution;
includes
Reasonably
Available
Control
Technology
and
other
measures.
In
the
case
of
PM10
,
it
refers
to
approaches
for
controlling
small
or
dispersed
source
categories
such
as
road
dust,
wood
stoves
and
open
burning.
RACT
(REASONABLY
AVAILABLE
CONTROL
TECHNOLOGY):
An
emission
limitation
on
existing
sources
in
non-attainment
areas,
defined
by
EPA
in
a
Control
Techniques
guideline
(CTG)
and
adopted
and
implemented
by
states.
Under
Title
I
of
the
CAAA,
EPA
will
establish
RACT
standards
for
marginal,
moderate
and
serious
non-attainment
areas.
RADIAL
BLADE:
Fan
wheel
design
with
blades
positioned
in
straight
radial
direction
from
the
hub.
RADON:
A
colorless,
naturally
occurring,
radioactive,
inert
gaseous
element
formed
by
radioactive
decay
of
radium
atoms
in
soil
or
rocks.
RANDOM
NOISE:
A
sound
that
has
an
average
amplitude
and
constantly
changing
frequency.
RANKINE:
See
Absolute
Temperature.
RAREFICATION:
A
phenomenon
related
to
negative
pressure.
When
air
is
drawn
out
through
resistance
into
a
fan
inlet,
the
air
is
stretched
out,
or
rarefied,
and
becomes
less
dense
than
at
the
entry
to
the
system.
While
negligible
at
low
pressures
and
volumes,
high-pressure
fan
selection
must
be
based
on
rarefied
inlet
density.
RE-ENTRAINMENT:
The
phenomenon
whereby
dust
is
collected
from
the
air
stream
and
then
is
returned
to
the
air
stream.
Occurs
when
dust
is
pulsed
from
a
bag
and
then
caught
up
by
an
upward
moving
air
stream.
REL
(RECOMMENDED
EXPOSURE
LIMITS):
Issued
by
NIOSH
to
aid
in
controlling
hazards
in
the
workplace.
These
limits
are
generally
expressed
as
eight
or
10
hour
TWAs
for
a
40-hour
work
week,
and/or
ceiling
levels
with
time
limits
ranging
from
instantaneous
to
120
minutes.
RELATIVE
HUMIDITY:
The
ratio
of
existing
water
vapor
to
that
of
saturated
air
at
the
same
dry-bulb
temperature.
REPEAT:
The
number
of
threads
in
a
weave
before
the
weave
repeats
or
starts
over
again.
The
number
of
ends
and
picks
in
the
repeat
may
be
equal
or
unequal,
but
in
every
case
the
repeat
must
be
in
a
rectangular
form.
REPLACEMENT
AIR:
A
ventilating
term
that
refers
to
the
replacement
of
air
lost
because
of
exhaust
air
requirements.
REPRESSURING
BAGHOUSE:
Baghouse
using
bags
that
are
cleaned
by
flowing
air
backwards
through
the
cloth.
Same
as
reverse
air
baghouse.
RESIDUAL
RISK:
The
quantity
of
health
risk
remaining
after
application
of
the
MACT
(Maximum
Achievable
Control
Technology).
RESPIRABLE
FRACTION:
The
size
range
of
particles
most
hazardous
to
health.
Includes
those
particles
which
are
both
small
enough
to
pass
through
the
human
body’s
biological
filters
and
large
enough
to
remain
in
the
lungs
rather
than
be
expelled.
The
respirable
fraction
generally
consists
of
particles
between
0.3
and
5
microns.
RESISTANCE:
In
air
flow,
it
is
caused
by
friction
of
the
air
against
any
surface,
or
by
changing
the
momentum
of
the
gas.
REVERSE
AIR
BAGHOUSE:
Baghouse
using
bags
that
are
cleaned
by
flowing
air
backwards
through
the
cloth,
to
cause
dust
cake
release.
REVERSE
JET:
See
Pulse
Jet.
REYNOLDS
NUMBER:
A
mathematical
factor
used
to
express
the
relation
between
velocity,
viscosity,
density
and
dimensions
in
a
system
of
flow.
Used
to
define
fan
proportionality.
RINGELMAN:
A
measure
of
the
opacity
caused
by
pollution
from
a
stack.
Grades
opacity
from
0
to
5,
where
0
is
an
invisible
discharge
and
5
is
totally
opaque.
RINGELMAN
CHART:
Actually,
a
series
of
charts
numbered
from
0
to
5,
that
simulate
various
smoke
densities,
by
presenting
different
percentages
of
black.
A
Ringelman
No.
1
is
equivalent
to
20%
black.
A
Ringelman
No.
5
is
100
percent.
They
are
used
for
measuring
the
opacity
of
smoke
rising
from
stacks
and
other
sources,
by
matching
with
the
actual
effluent,
the
various
numbers
or
densities,
indicated
by
the
charts.
Ringelman
numbers
were
sometimes
used
in
setting
emission
standards.
ROTARY
AIRLOCK:
A
valve
with
a
rotating
wheel
generally
located
on
the
dust
collector
discharge
hopper
or
at
the
end
of
a
screw
conveyor.
It
is
designed
to
allow
continuous
discharge
of
the
collected
dust
while
maintaining
a
positive
air
seal.
ROTOR:
The
rotating
part
of
most
AC
motors.
RPM:
Revolutions
per
minute.
RTECS
(REGISTRY
OF
TOXIC
EFFECTS
OF
CHEMICAL
SUBSTANCES):
A
database
that
lists
an
identification
number,
synonyms,
Department
of
Transportation
(DOT)
hazard
label
information,
EPA
Toxic
Substances
Control
Ad
(TSCA)
information,
OSHA
and
Mine
Safety
and
Health
Administration
(MSHA)
air
exposure
limits
and
animal
and
human
toxicologic
data.
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