United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S4-83-010 June 1983
Project Summary
Validation of Samplers for
Inhaled Paniculate Matter
Walter John, Stephen M. Wall, and Jerome J. Wesolowski
Methods for testing inhalable par-
ticle samplers have been developed
and applied to the dichotomous sam-
pler and the size-selective hi-vol sam-
pler. The sampling effectiveness of the
inlet to the dichotomous sampler was
measured and found to be excessively
dependent on wind speed. A modifica-
tion to improve the performance was
designed as a retrofit to the existing
inlet Measured wall losses in the
dichotomous sampler were small. The
fine fraction is found to be correlated
to error in nozzle concentricity, which
is not within specifications for the
typical commercial sampler.
Penetration of the size-selective hi-
vol by solid particles largerthan the 15-
/xm cutoff was measured by three
methods. Near the cutoff, monodis-
perse spray-dried particles that were
sized aerodynamically by a new laser
sedimentation velocimeter were used.
In the 35 to 60 jam range, glass beads
and A/C test dust particles were pro-
duced by a new sonic fluidized micro-
bed generator. Finally, ambient par-
ticles that were collected on a Nucle-
pore after filter were analyzed by scan-
ning electron microscopy. All three
tests show that excess penetration of
the size-selective hi-vol by solid par-
ticles was acceptably small. Additional
testing was conducted in ambient air
using an array of side-by-side samplers
including two dichotomous samplers,
two monocut samplers, and a cyclone
sampler.
This Project Summary was developed
by the Environmental Monitoring Sys-
tems Laboratory, Research Triangle
Park North Carolina, 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
The Environmental Protection Agency
(EPA) is considering revisions to the
National Ambient Air Quality Standards
(NAAQS) for paniculate matter. Once
promulgated, the revised standards would
regulate only those particles that can be
deposited in the human respiratory sys-
tem. The rationale for a standard for
inhalable particles, those particles smaller
than 15 jam aerodynamic diameter,*
which are deposited in the respiratory
system below the trachea, has been pre-
sented by Miller, et al.
A network of inhalable particle sam-
plers has been deployed across the United
States by the Environmental Monitoring
Systems Laboratory at Research Triangle
Park, North Carolina (EMSL/RTP) to field
test the sampling methodology and to
acquire a data base in support of the new
standard. Early results revealed that the
samplers have some technical problems.
These experiences emphasize the need
for rigorous testing of the new samplers
because they will generate data that will be
the basis for control decisions.
During the present project, the dicho-
tomous and size-selective hi-vol samplers
used in the EPA network were tested in
the laboratory. Additional testing was
carried out on side-by-side samplers in
ambient air. The new testing methods that
were developed include measurement of
nozzle alignment in the dichotomous sam-
pler, precision wall loss measurements,
and tests for particle bounce. These
'After the present work was completed, the EPA staff
recommended a cutpoint of 10 /u.m for the revised
paniculate matter standard. Modified versions of the
1 5 Mm samplers are now available. Some, but not all,
of the test results presented here are outdated, but the
test methodology is still current.
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methods should be useful for the formu-
lation of acceptance criteria for new can-
didate samplers and for quality assurance
testing of commercial samplers.
Results
Laboratory testing of the dichotomous
samplers included measurement of the
critical dimensions of the inlets and the
virtual impaction stage, determination of
the effect of wind speed on the effective-
ness of inlet sampling, and precision
measurement of the wall losses in the
samplers. Testing of inlets to commercial
dichotomous samplers reveals that the
critical dimensions adhere closely to man-
ufacturing tolerances. However, wind
tunnel and static chamber tests reveal that
the inlet sampling effectiveness is exces-
sively dependent on wind speed. Flow
visualization studies show strong chan-
neling of the flow inside the inlet A
theoretical model including inertial and
gravitational forces accounts for the test
data and provides a basis for an inlet
modification consisting of an enlarged
entrance slit and an inertial impactor.
Tests of two variations of this modification
show that this is a promising approach
that permits a low-cost retrofit to existing
inlets. The design also facilitates a change
in particle size cutpoint
The cutoff (coarse fraction vs. particle
diameter) for the virtual impaction stage of
the dichotomous sampler was measured
with DOP-uranine aerosol. The results
agreed with independent measurements
by Loo and by McFarland. A casting
method was developed to measure the
critical dimensions of the dichotomous
sampler stage. The nozzle concentricity
was out of tolerance in three out of five
samplers. Design faults were revealed
and a simple method was suggested for
improvement of the concentricity.
Laboratory tests with monodisperse
aerosol show that the 50% particle size
cutpoint of the impactor stage of the
dichotomous samplers averages 2.4 ju.m
and the wall loss at the cutpoint averages
2.3%, both acceptable figures. Wall losses
peaked at the cutpoint and increased again
above 10 jum. Most of the losses were on
the collection nozzle (Figures 1 and 2).
While the wall losses were small for 3-jum
particles, the fine fraction correlated with
error in nozzle concentricity (Figure 3);
therefore, close adherence to the toler-
ance on the nozzle concentricity is recom-
mended. The magnitude of the wall loss
agreed with the measurements by Loo but
did not agree with the results of McFarland
The losses at 2.5 ju.m are about twice as
large as those reported by Loo for the
prototype. This increase is probably caused
by larger tolerances in the commercial
samplers for nozzle concentricity and col-
lection nozzle profile. However, the wall
j.7 a
7
Beckman
Sierra
Figure 1. Schematic drawing of dichot-
omous sampler impactor parts
that were washed separately to
recover wall losses.
1.0
0.1
0.01
1 10
Aerodynamic Diameter, urn
Figure 2. Wall losses measured for indi-
vidual parts of the dichotomous
samplers (parts are labelled as
in Figure 1).
WT = Total wall loss
+ We + We + Wo>.
losses are acceptable in the commercial
units. The high precision of the measure-
ments obtained with standard laboratory
equipment indicates that the present meth-
odology provides a basis for a standard
approach to sampler wall loss measure-
ments.
Laboratory testing of the size-selective
hi-vol sampler inlet included measure-
ment of sampling effectiveness for liquid
particles and determination of excess pen-
etration by large solid particles. Measure-
ments made with DOP-uranine to test the
sampling effectiveness of the size-selective
hi-vol inlet under static conditions agreed
with previous measurements made by
Wedding and by McFarland and Ortiz in a
wind tunnel at 2 km/h. These data and the
previously described results for the dicho-
tomous sampler show that independent
laboratories can use liquid aerosols to
obtain consistent results for cutoff and
effectiveness measurements.
Three methods have been developed for
measurement of the penetration of a size-
selective sampler by large solid particles.
(1) Near the cutoff, monodisperse spray-
dried particles were used from a vibrating
orifice aerosol generator and sized aero-
dynamically with a laser sedimentation
velocimeter. (2) Particles much larger
than the cutoff were produced by a new
sonic fluidized microbed generator using
presized samples of glass beads and A/C
test (Arizona Road) dust (3) Penetration
by large ambient particles was measured
by microscopy after they were collected on
a Nuclepore after filter.
The three methods were applied to the
size-selective hi-vol sampler. Method 1
indicated a 25% excess penetration by
solid vs. liquid particles at the 15-fim
cutpoint (Figure 4). However, this pene-
tration would not ordinarily lead to a serious
error in sampled mass because the cut-
point for solid particles (1 7 jum) is only
slightly larger than 15 /im and the test
particles are bouncier than most ambient
particles. Method 2 showed 3 to 4%
penetration (by mass) of particles that had
aerodynamic diameters in the range of 35
to 60 jum (Figure 5). Seven percent
penetration was observed for 62 /im A/C
test dust particles, but this may be caused
by breakup of the particles, an inherent
problem with A/C test dust Glass beads
were excellent test particles. Examination
of the impaction plate showed that the
particles did not adhere to the plate in the
impaction zone but were collected near
the bases of the collection tubes. There-
fore, the particles bounced, but were not
reentrained in the exit flow. Method 3
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20
3.0 fan DOP—Uranine
.§'
.8
10
0
to
0.75
0.5
0.25
I
A
R= 0.97
A
R = 0.94
^ s
Tolerance
I
50 100 150
Error in Nozzle Concentricity, ftm
Figure 3. A: Fine fraction of the dichotomous sampler vs. error in nozzle concentricity.
B: Wall loss vs. error in nozzle concentricity.
gave a penetration efficiency of 5% for
ambient particles that had aerodynamic
diameters greater than 30 /xm; these
results agree with those of method 2.
Ambient air testing on side-by-side
samplers shows that the standard devia-
tion of the coarse fraction of the dicho-
tomous sampler is more than twice that of
the fine fraction and nearly twice that of
the monocut samplers. The fine fractions
correlated closely with the mass concen-
tration from the Air and Industrial Hygiene
Laboratory (Al H L) cyclone, and the su m of
the coarse and fine fractions correlated
closely with the mass concentration from
two monocut inhalable particle samplers.
One dichotomous sampler had a consis-
tent bias of about -10% relative to the
other samplers; the cause of this bias was
undetermined.
Conclusions and
Recommendations
The experience from the validation pro-
gram for inhalable particle samplers em-
phasizes the importance of rigorous test-
ing. Precise tests with laboratory aerosol
can lead to correction of problems before
costly tests are conducted in ambient air.
Sampler inlets need to be wind tunnel
tested to verify that wind speed sensitivity
is within acceptable limits. Low wind
speeds (not more than 2 km/h) should be
included to ensure that particle sedimen-
tation within the inlet is not significant.
Samplers should be tested with mono-
disperse liquid particles for efficiency and
wall loss measurements and with solid
particles to determine possible excess
penetration resulting from bounce and
reentrainment.
This study resulted in the development
of several testing techniques which are
recommended for future work. The method
for wall loss measurements is capable of
accuracies approaching 0.1 % and requires
only standard apparatus. Three methods
for measurement of solid particle penetra-
tion have been developed.
Additional work is needed for adapta-
tion of the laboratory solid particle tests
used in wind tunnel testing. Static sam-
pling is sufficient for testing of an impac-
tion stage in a sampler. Use of A/C test
dust is not recommended because of its
friable nature.
The following recommendations are
based on the current test results:
(1) The inlet to the dichotomous sam-
pler should be replaced with one
that is insensitive to wind speed.
(2) Accurate nozzle alignment in the
commercial dichotomous samplers
should be ensured by the simple
design change identified in the
research report.
(3) The size-selective hi-vol, which per-
formed well under all testing, should
continue to receive consideration as
a candidate sampler.
References
Miller, F. J., D. E. Gardner, J. A. Graham,
R. E. Lee, Jr., W. E. Wilson, and J. D.
Bachman. Size Considerations for
Establishing a Standard for Inhalable
Particles. J. Air Poll. Control Assoc.
29:610-615, 1979.
Suggs, J. C., C. E. Rodes, E. G. Evans, and
R. Baumgardner. Inhalable Particulate
Network, Annual Report: Operation and
Data Summary, April 1979-June 1980.
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g
I
700
80
60
40
20
\ \ I I I I I I I
• John & Wall
Okm/h
OOP
D John & Wall
Okm/h
Potassium biphthalate
- X
Wedding
2km/h
Oleic acid
McFarland & Ortiz
2km/h
Oleic acid
I
D
I I I I
4 6 8 10
Aerodynamic Panicle Diameter,,
20
40
Figure 4.
Sampling effectiveness of the size-selective hi-vol measured at zero wind speed
for liquid (OOP) and solid (potassium biphthalate) particles. Data from wind tunnel
tests at 2 km/h wind speed are shown for comparison.
EPA-600/4-81-037, U.S. Environmental
Protection Agency, Research Triangle
Park, NC 27711.
Loo, B. W., Unpublished progress report
to C. E. Rodes.
McFarland, A. Unpublished progress
report to C. E. Rodes.
McFarland, A. R. and C. A. Ortiz. Progress
Report -- Aerosol Characterization of
Ambient Particulate Samplers Used in
Experimental Monitoring Studies. Texas
A & M University Research Foundation,
College Station, Texas, October 1979.
Wedding, J. B. Unpublished progress
report, Colorado State University, Ft.
Collins, Colorado, 1981.
10
0 Glass Beads
X A/C Test Dust
i
Figure 5.
20 40 60 80
Aerodynamic Diameter, urn
Penetration of the size-selective hi-vol by large glass beads and A/C test dust.
4
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W. John, S. M. Wall, and J. J. Wesolowski are with Air and Industrial Hygiene
Laboratory, California Department of Health Services, Berkeley, CA 94704
Ralph Baumgardner is the EPA Project Officer (see below).
The complete report, entitled "Validation of Samplers for Inhaled Paniculate
Matter," (Order No. PB 83-191 395; Cost: $11.50. 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:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
. S. GOVERNMENT PRINTING OfFKt 1983/659-095/1953
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