United States
Environmental Protection
Agency
Atmospheric Research and Exposure
Assessment Laboratory
Research Triangle Park. NC 27711
Research and Development
EPA/600/S3-90/057 Aug. 1990
Project Summary
Application Guide for
Measurement of PM2.5 at
Stationary Sources
Sherry S. Dawes and William E. Farthing
This manual presents two options
which allow determination of
stationary source PM2 5 emissions.
PM2.s can be measured in
conjunction with PM10 and it can be
measured as PM2.5 only. When
determination of both PM2s and PM10
is the object of a test series, either
the Constant Sampling Rate (CSR)
procedures or the Exhaust Gas
Recycle (EGR) sampling system can
be used. When PM2 5 is the only size
fraction of interest the CSR
procedures are selected. This
application guide should be used as
a companion to the application
guides for CSR and EGR. With all of
the options, stack gas is sampled at
multiple points using an in-stack
inertial sampler with a constant flow
rate. The operating principle of the
CSR procedures limit errors due to
anisokinetic sampling to within
specified limits related to the
maximum particle size of interest. For
PM2 5 measurements only, the
maximum allowable error due to
anisokinetic sampling is 10% for 2.5
nm particles. The range of duct
velocities permitted for a nozzle with
this maximum allowable error is
broad enough that rarely is it
necessary to break a traverse into
subtraverses with different sampling
nozzles.
The sampling device described in
this manual is Cyclone IV of the
SRI/EPA five-stage series cyclone.
This device provides a 2.5 urn size
cut at a flow rate of approximately
0.36 dscfm; the precise flow rate
depends on local stack conditions.
These procedures specify the
precise flow rate for PM2 5
measurements when Cyclone IV is
used alone and for both PM10 and
PM25 measurements when Cyclone
IV is used in conjunction with
Cyclone I as a two stage inertial
sampler
This Project Summary was
developed by EPA's Atmospheric
Research and Exposure Assessment
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
Airborne particulate matter of less than
2.5 urn aerodynamic diameter is of
interest because these particles are
respirable. Measurement of source
particulate emissions in this size band
(PM2s) is subject to much the same
considerations as particulate matter of
less than 10 nm aerodynamic diameter
PMi0 and, therefore, will require similar
sampling procedures.
Two methods have been developed for
determination of PM10 emissions. One
method uses the principle of Exhaust Gas
Recycle (EGR) to meet the constraints of
particle sizing (constant flow rate through
the sampling device) and representative
sampling (isokinetic sampling at the
number of traverse points prescribed by
Method 1). The second method, Constant
Sampling Rate, (CSR), limits error due to
anisokinetic sampling and spatial
variation to the level of more intrinsic
errors, such as source fluctuations. A
complete traverse of the sampling plane
is synthesized from one or more runs
operated within these limits. Although
greater accuracy in mass concentration is
achieved by the more stringent limits on
isokinetic sampling exercised by the EGR
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method, development of new sampling
hardware is required. The CSR method,
on the other hand, uses existing Method
5 or Method 17 hardware.
Two options for PM25 sampling are
considered here: (1) measurement of
PM2 5 in junction with PM10 and (2)
measurement of PM2 5 only. When
determination of both PM2 5 and PM10 is
the object of a test series, either CSR or
EGR can be used. The procedures
required for each method will be
described in this text. When PM2 5 is the
only size fraction of interest, the effects
of anisokinetic sampling are much less
significant; consequently, the greater
accuracy achieved by the EGR method
becomes insignificant. For this reason,
only CSR procedures will be described
for this option.
This manual should be used as a
companion to the operator's manuals for
CSR and EGR for PM10 measurement.
Text here is confined to those changes in
procedure or hardware required to
measure PM25. To simplify incorporating
information presented here with EGR or
CSR operating procedures for PM10, this
manual is organized in a manner identical
to the PM10 operating manuals,with one
significant difference. Because two
options are available to the operator when
sampling for PM25, certain sections of
the text will be repeated to present the
procedures for each option separately
and completely. F:or example, Section 5A
presents setup calculations for
measurement of PM2 5 only, and Section
5B presents these same calculations for
measurement of PM25 along with PM10.
Other than this duplication, all sections of
the CSR and EGR manuals are
incorporated into the outline for this
manual, including Operating Principles,
Hardware Requirements, Calibration,
Pretest Activities, Sampling Parameters,
Taking the Sample, Sample Retrieval,
Postsampling Checks, Data Analysis,
Maintenance, Audit Procedures, and
Recommended Standards for Trace-
ability.
Operating Principles
The most significant difference
between the PM10 sampling techniques
previously developed and the PM2 5
methodology described in this manual is
the two options (measurement of PM25
only or measurement of PM2 5 in
conjunction with PM10) available to the
operator when sampling for PM25. The
operating principles must encompass
both of these options. Generally, the
principles of operation for the PM10
samplers ensure at worst comparable
accuracy for PM25 sampling. Typically,
errors in PM2 5 from anisokinetic
sampling will be significantly less than for
PM10. The lower inertia of PM25 would
lead one lo expect less stratification of
particle concentration across a duct than
with PM10 Unfortunately, there are not
sufficient data available to evaluate this
effect. Therefore, the number of traverse
points specified by the chosen sampling
method (EGR or CSR) for measurement
of PM10 vvill be required for PM2 5
whether measured in conjunction with
PM10 or not.
Sampling Hardware
The sampling system used to measure
PM25 for either the CSR or EGR method
is the same as for PM10 with the
exception of the particle sizing device.
The only device that has been developed
for the EGR method at present is a two-
stage cyclone (one stage to cut at 10 ^m
and one stage to cut at 2.5 nm). For the
CSR method, more choices exist. When
PM2 5 is the only size fraction of interest,
a single-stage cyclone or a cascade
impactor may be used as the sampling
device. When determination of both
PM2 5 and PM10 is the objective of a test
series and CSR is the chosen operating
method, either a two-stage cyclone or a
cascade impactor may be used as the
sampling device. However, while cascade
impactors have been recognized as
viable sampling devices for the
measurement of PM25 and PM10 they
are not recommended for widespread
use because of the potential for error and
interferences inherent in such devices.
These problems would tend to increase
the concentration at smaller particle
diameters which can be critical to
measurements of this type. To avoid
these errors, an experienced operator is
required.
One sampling device known to meet
PM2 5 cyclone performance specifi-
cations is the commercially available
version of Cyclone IV, the fourth stage of
the SRI/EPA Five-Stage Series Cyclone.
Laboratory calibrations have shown that
Cyclone IV produces a 2.5 pm D50 at a
flow rate of approximately 0.36 dscfm.
The basic principles of system
operation for either the CSR or EGR
sampling method are unchanged by the
addition of PM25 to PM10 However,
experience has shown that, in most
situations, the stages of a sampling
device will not follow exactly the same
scaling laws with respect to changes in
cut diameter when changes in operating
conditions occur. Consequently, when the
two-stage cyclone sampler is used,
obtaining data for both size fractions that
meet the acceptance criteria for both
measurements and provide the maximum
tolerance for measurement error will
require some compromise between these
two flow rates. A number of approaches
may be used to choose a flow rate within
the limits of tolerance for both the PM10
and PM2 5 cyclones that would maximize
the allowable tolerance. The approach
chosen for this manual translates the
limiting flow rates into the corresponding
Cyclone I D50's, chooses a D50 within the
calculated range, and converts the
chosen D50 into the corresponding flow
rate. This approach is presented for both
CSR and EGR setup calculations.
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Sherry S. Dawes and William E. Farthing are with Southern Research Institute,
Birmingham, AL 35255-5305.
Thomas £. Ward is the EPA Project Officer (see below).
The complete report, entitled "Application Guide for Measurement of PM2.5 at
Stationary Sources," (Order No. PB 90-247 198/AS; Cost: $23.00, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-90/057
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