COLLABORATIVE STUDY
                         of
   REFERENCE METHOD  FOR THE DETERMINATION
OF SUSPENDED PARTICULATES IN THE ATMOSPHERE
             (HIGH VOLUME METHOD)

                    Herbert C. McKee
                    Ralph E. Childers
                    Oscar Saenz, Jr.

                  Contract CPA 70-40
                  SwRI Project 21-2811
                      Prepared for
           Office of Measurement Standardization
             Division of Chemistry and Physics
                Air Pollution Control Office
              Environmental Protection Agency
                       June 1971
            SOUTHWEST  RESEARCH  INSTITUTE
            SAN  ANTONIO                       HOUSTON

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                     COLLABORATIVE STUDY
                                 of
         REFERENCE METHOD  FOR THE  DETERMINATION
      OF SUSPENDED PARTICULATES IN THE ATMOSPHERE
                     (HIGH VOLUME METHOD)

                            Herbert C. McKee
                            Ralph E. Childers
                            Oscar Saenz, Jr.

                          Contract CPA 70-40
                          SwRI Project 21-2811
 ^                           Prepared for
 x.                 Office of Measurement Standardization
                    Division of Chemistry and Physics
                       Air Pollution Control Office
 V"                   Environmental Protection Agency
\                             June 1971
si
                                  Approved:
                                  Herbert C. McKee
                                  Assistant Director
                                  Department of Chemistry
                                  and Chemical Engineering

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                               SUMMARY AND CONCLUSIONS
      This report presents information obtained in the evaluation and collaborative testing of a method to
measure the mass concentration of suspended participate matter in the atmosphere. Minor variations of this
method  have  been used extensively by the National Air Sampling  Network and by state  and local air
pollution control agencies for approximately 15 years.

      This method was recommended as a tentative standard method by the Intersociety Committee, a
cooperative group consisting of representatives of eight scientific and engineering societies.* It was pub-
lished as Tentative Method 11101-01-70T in Health Laboratory Science, October 1970, pp 279-286. It was
then tested as a part of this program, by means of a collaborative test involving 12 laboratories. A statistical
analysis of the data obtained provided the following results:

      •    The relative standard deviation (coefficient of variation) for single analyst variation  (repeat-
           ability of the method) is 3.0 percent.

      •    The relative standard deviation for  multilaboratory variation (reproducibility of the method) is
           3.7 percent.

      •    The minimum detectable amount of particulate matter is 3 mg (95 percent confidence level).
           This is equivalent  to  l-2jug/m3 for a 24-hr sample. Values this low will rarely, if ever, be
           observed in the atmosphere, and thus lack of sensitivity does not limit the use of this method
           for ambient air quality measurement.

      These results show that the method can  give very good precision when followed rigorously. At the
same time, it is rugged, and variations in procedure and technique can occur with only a minor effect on the
results.

      Based on these  results, this method was adopted as  a standard method for the measurement of
suspended particulate  matter in the atmosphere by the Standardization  Advisory Committee of the Air
Pollution Control  Office,  Environmental Protection Agency. It was published in the Federal Register,
April  30, 1971, and is reproduced as Appendix A of this report.
*  Air Pollution Control Association
   American Chemical Society
   American Conference of Governmental Industrial Hygienists
   American Industrial Hygiene Association
   American Public Health Association
   American Society for Testing and Materials
   American Society of Mechanical Engineers
   Association of Official Analytical Chemists
The Intersociety Committee receives partial financial support through APCO Contract 68-02-0004.
                                                in

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                                    ACKNOWLEDGMENT
     The authors  wish  to express appreciation to the Project Officer, Mr. Thomas W. Stanley, and staff
members of the Office of Measurement Standardization, APCO, for assistance in planning the collaborative
study and in site preparation and preliminary sampling. Through this work, adequate space and facilities
were made available for  the sampling, which was performed simultaneously by twelve participating labora-
tories, and for the calibration and other supplementary work which was required.

     The assistance and cooperation of the participating laboratories is also acknowledged with sincere
appreciation  for the  voluntary efforts of the staff members  who  represented each organization. The
representatives and organizations participating in the collaborative test program were as follows:
                       Name
            Organization
                Harold K. Beatty
                J. H. Blacker
Department of Environmental Control
Chicago, Illinois

Esso Research and Engineering Co.
Linden, New Jersey
                Walter W. Cooney
                Robert C. Crabtree
                Edward J. Hanks, Jr.
                W. Kenfield
State of Maryland
Division of Air Quality Control
Baltimore, Maryland

Jefferson County, Kentucky
Air Pollution Control District
Louisville, Kentucky

Air Pollution Control Office
Research Triangle Park, North Carolina

Montgomery County, Ohio
Air Pollution Laboratory
Dayton, Ohio
                Rudy Marek, Jr.
Southwest Research Institute
Houston, Texas
                M. R. Midgett
Air Pollution Control Office
Cincinnati, Ohio
                Frank G. Norris
City of Steubenville
Air Pollution Department
Steubenville, Ohio
                                               IV

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       Name
           Organization
James M. Peters
I. A. Schwabbauer
Van A. Wheeler
University of Texas at Austin
Austin, Texas

University of Iowa
Iowa City, Iowa

Air Pollution Control Office
Cincinnati, Ohio

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                                    TABLE OF CONTENTS

                                                                                           Page

I.    INTRODUCTION	      1

II.   EVALUATION OF THE METHOD	      2

     A.   Calibration of Flow Rate	      2
     B.   Selection of Sampling Locations	      2
     C.   Effect of Possible Volatilization	      3

III.  COLLABORATIVE TESTING OF THE METHOD	      4

     A.   Selection of Collaborators	      4
     B.   Planning the Test Series	      5
     C.   Site Evaluation	      6
     D.   Conducting the Test Series	      6
     E.   Summary of Statistical Analysis	      7
     F.   Calibration Errors	      9

APPENDICES

     A.   Reference Method for the Determination of Suspended Particulates in the Atmosphere
          (High Volume Method)	    A-l
     B.   Statistical Methods	    B-l
                                              vu

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              I.  INTRODUCTION

      Of all the various methods available to measure
 atmospheric contaminants, the so-called High Volume
 Method  (frequently  called  "Hi Vol"  Method)  has
 probably been used more extensively than any other.
 One reason for this is the widespread occurrence of
 dust and particulate matter in the atmosphere, with
 measurable  quantities  occurring  as  natural back-
 ground even in remote areas. Another reason is that
 the  equipment required  is relatively inexpensive,
 whereas the measurement of other contaminants may
 require much more expensive  and elaborate instru-
 ments. First  developed by the predecessor organiza-
 tion of the present EPA Air Pollution Control Office
 in the mid-1950's, this method has  been used on a
 large scale by the National Air Sampling Network for
 approximately 15 years.  Many state  and local air
 pollution control agencies have also used this method,
 or variations of it,  for monitoring networks to supple-
 ment the Federal effort.

      The High Volume Method can be used by any
 laboratory possessing normal equipment and skills if a
 minimum of special purpose equipment is added. A
 sampler capable of pulling air through a filter medium
 is used to  collect the dust and particulate  matter,
 which  is then measured  on a weight basis. Chemical
 analysis of the  collected deposit is  also possible  to
 measure various constituents such as metals,  nitrate,
 sulfate, etc. (Analytical procedures for such analyses
 are not included  in  this  standard  method  at  the
 present time.)

     Since no standardized procedure has been avail-
 able to guide different laboratories in the  use of this
 method,  each laboratory  has  had to  develop  and
 evaluate different techniques for weighing filters, cali-
 brating  flow  rates, and  other  details in conducting
 tests. As an example, only 40 percent of the collabo-
 rators in this  test  were routinely  using a procedure
essentially similar  to  the method tested. Less than
half had access to a positive displacement meter  to
 use as  a  primary  standard for calibration. While
 80 percent had some sort of orifice calibration unit,
only  10 percent indicated that it was ever calibrated
using a primary standard of any kind. The calibration
of a sampler was indicated to be  a standard practice;
however,  only 20 percent  calibrated routinely on  a
monthly basis  and 40 percent on a yearly basis. The
remaining 40 percent did not calibrate  on any pre-
determined schedule.

      In order to obtain  comparable data  so  that
interlaboratory comparisons would  be  feasible,  the
Air Pollution Control Office has been working for
some time to develop standard methods which could
be  used by  all persons making air quality measure-
ments. A number of scientific and engineering societies
have also been  active in the development of standard
methods, including several of those now participating
in the  Intersociety Committee, whose members are
listed in the Summary and Conclusions.

      Following the  development  of a tentative stan-
dard method by the Intersociety Committee, the final
step in the  standardization process is to conduct  a
collaborative test, or interlaboratory comparison, of
the proposed standard method. This procedure, also
called "round-robin testing," has been used to evaluate
many  different methods of  measurement in such
diverse fields as water chemistry, metallurgy, paint and
surface coatings, food and related products, and many
others. A test of this nature  by a representative group
of laboratories is the only way that the statistical limits
of error inherent in  any method can be determined
with sufficient confidence.

      This  report presents  the  results  of a  col-
laborative test of  the High Volume Method con-
ducted  by Southwest Research Institute  and the  Air
Pollution Control Office, together with the statistical
analysis of the  data obtained. In planning for the col-
laborative test, it was necessary  to evaluate several
aspects  of the recommended method with respect to
flow rate  calibration and other details. The informa-
tion obtained in  this evaluation is also  presented as
background  information relating to  the collaborative
test program and as information helpful  in under-
standing the  capabilities and limitations of this stan-
dard method.

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    II.  EVALUATION OF THE METHOD

      Since the High Volume Method has been used
by many laboratories, it is not surprising that many
different variations of  this method  have  occurred,
especially in flow rate calibration and other details of
measurement.  To aid in  resolving some of these dif-
ferences, an evaluation of the method was performed
during the development of  plans for collaborative
testing  This section of  the report presents the data
obtained in some of these tests and discusses the
importance of different procedures in planning a col-
laborative test and in evaluating the  capabilities and
limitations of the method itself.

A.    Calibration of Flow Rate

      In calibrating the flow measuring system of the
sampler, it is necessary to vary the flow rate over the
operating range  of the  sampler in order to obtain
accurate  calibration. In  the past,  most workers have
done  this by  either of two  methods: (l)use of a
series of perforated plates in place of the filter used
for  sample  collection, to vary resistance to flow (as
presently shown in the method); or (2) use of a vari-
able transformer to change  the voltage applied to the
blower motor, thus varying the speed of the blower
and   changing  the  flow  rate. However,  recent
workO)* indicated that varying the speed of the
blower led  to possible errors, especially at low flow
rates, because this changed the  flow pattern through
the  sampler, which in turn caused  changes in the flow
pattern past the variable-orifice  meter located on the
discharge side of the blower. Therefore, both  pro-
cedures  were evaluated to  see if  errors would occur
with the method of calibration specified in the pro-
posed method.

      Two   types  of  high volume  samplers  were
checked. The first was equipped with a rotameter for
flow measurement, and the second had an orifice on
the  discharge side of  the blower  for continuous
recording of flow rates.  With both types of sampler,
flow  rate was varied by using resistance  plates,  as
specified in the method, and by using a variable trans-
former to vary the speed of the  blower. No differ-
ences were observed with the sampler equipped with
a rotameter for flow measurement. Identical readings
were obtained throughout the  range of flow rate (30
to 65 cfm), regardless of whether the flow was varied
by using the resistance plates or by controlling blower
speed. With the other sampler, however, this was not
the case.  Identical readings  were  obtained  at the
higher flow rates, but at lower flow rates a difference
was observed. In all  cases, the indicated  flow was
lower when the voltage  was varied than when the
resistance plates were used. The differences were not
great, ranging from 2 cfm at the low rate of 30 cfm to
no difference at 60 cfm. However, this confirmed the
fact that some error may  occur with this method of
calibration, as was indicated  by the  University of
Cincinnati results, and, therefore,  the Intersociety
Committee deleted the optional calibration procedure
based on voltage  variation. The  use  of resistance
plates was specified as the standard method of vary-
ing flow during calibration and  is included in the
method as now published. This method was used dur-
ing the collaborative test of the method.

B.    Selection of Sampling Locations

      A standard method can be developed to specify
details of calibration, flow measurement, analysis of
samples, etc., in considerable detail, and the  statistical
accuracy of these various procedures  can  be estab-
lished. In the  measurement of total particulate mat-
ter, however,  a serious  problem exists which is not
subject  to statistical  evaluation,  except  in  rather
general terms. Since particulate matter is a ubiquitous
constituent of the atmosphere, and, since the amount
varies widely  from place  to place, the selection of
sampling times and locations is  a matter of para-
mount importance. This cannot be  standardized in a
specified method, but some general guidelines can be
given to indicate how these factors  will influence the
results obtained.

      Measurements of total particulate matter by the
High Volume method are  usually  made  to determine
*Superscript numbers in parentheses refer to the List of References.

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overall  community-wide patterns which exist.  How-
ever, if the results obtained  in any one location are
influenced to a major degree by a  significant source
of dust  located nearby, then the results will be typical
of dust  levels over an extremely small area rather than
the  portion  of the community  which  a particular
monitoring station should represent.

      This means, then, that if a monitoring station is
intended to represent typical levels  over  a large area,
it should  be placed in a location free of local  inter-
ferences. The most obvious interferences to avoid are
unpaved  streets  and  parking  lots,  a major  dust-
emitting  industrial plant  that  would constitute a
single dominant  source, nearby  construction activi-
ties, and  other obvious sources which affect only
limited  geographical areas.

      No specific figures can  be given for the amount
of interference which such  sources can cause  since
this  may  vary  over  many  orders  of magnitude,
depending on the  nature of the source and on  the
distance from  the  source  to the sampling location.
However,  samples showing  several hundred or even a
few  thousand micrograms  per cubic  meter  (jug/m3)
have been collected directly downwind from obvious
sources  of  this  nature(2,3); which  indicates  that
values can be  obtained which are  several times  the
community-wide levels that usually exist.

      Another  important variable  in  some  circum-
stances  is  the height of the sampler above the ground.
Dust  raised by automobile traffic  and other extra-
neous sources frequently contains a large proportion
of relatively large particles which settle  back to  the
earth fairly  rapidly, and therefore would not be col-
lected by  a sampler located some distance above  the
earth's surface. In one study'2), for  example, samples
were collected 3 ft and 30 ft  above  ground level next
to a paved street with a light deposit of dust on  the
surface  of the  pavement  from nearby construction
activity; values obtained at the upper level averaged
about 50 percent of those obtained at the lower level.
In another study(^), 24-hr  samples  were collected in
four cities at levels of 3 ft  and  30 ft; in this case,
average  values  for the four locations indicated that
samples collected  30 ft above  ground level  showed
from 60 percent to  90 percent of the dust loadings
measured 3 ft above ground level.

      If samples are  obtained  for less than  a  24-hr
period, the time of day is also an important variable.
This is illustrated  by samples collected at 3-hr  inter-
vals which show very low levels at night, occasionally
in the range of rural background levels such as  20 to
40 jUg/m3. During  daylight hours, however, values are
usually much higher due to vehicular traffic and  other
human activities,  frequently reaching 3-hr levels as
much as four to five times the nighttime values! v
This shows the desirability of collecting 24-hr samples
to evaluate overall  conditions in the community.

      As stated previously, no specific standard pro-
cedures can be given to  compensate  for these  prob-
lems. However, a  considerable  degree of judgment
and  experience must be utilized in the selection of
sampling locations and in the evaluation  of data to
avoid reaching erroneous conclusions because of near-
by sources of dust which may exert an undue  influ-
ence  on  sampling  results.  Since the  objective  of a
monitoring  network  usually is to determine  com-
munity-wide levels,  sampling  locations  should be
chosen to  avoid   excessive  influence from a  single
dominant  source  immediately  adjacent  to  the
sampler.

      To conduct  a collaborative  test,  results  were
needed which would be representative of particulate
levels over a considerable area and which would not
be unduly influenced by a single source. As discussed
later, a location was selected which appeared to meet
this requirement.

C.    Effect of Possible Volatilization

      As  outlined  in the  method, filters should be
equilibrated   in  the laboratory  for  24 hr  prior to
weighing, or reweighing after sampling, to determine
the weight  of material  collected.  During  the pre-
liminary sampling prior to collaborative testing, filters
were kept and reweighed after succeeding intervals of
time to obtain some information on possible changes.

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       TABLE I. SUMMARY OF PRELIMINARY
         DATA FOR SAMPLING OF PARTICU-
            LATES AND THE EFFECT OF
              EQUILIBRATION TIME
            Parnculate Concentration, ng/m3

Sampler
Number*

1
•>
3
4
5
First Day
Equilibration
Time
1-Day
95
100
85
96
92
4 5 -Day
89
88
76
83
82
Second Day
Equilibration
Time
1-Day
80
73
82
83
80
4 5-Day
75
69
75
76
76


Third Day
Equilibration
Time
2-Day
82
73
83
77
82
5 5-Day
76
69
79
73
78

Table I tabulates the results of these tests. After an
additional  3.5 days of  equilibration, the indicated
concentration of particulate matter had decreased by
5 percent or more. It is presumed that this was due to
evaporation of volatile  "tarry" organic materials or
loss of water from the filters, with the tarry materials
being the more probable explanation. No completely
satisfactory method exists to compensate for these
changes, but this factor emphasizes the importance of
observing the 24-hr time limit specified in the method
if the results are to be comparable from one series of
tests to another. If the presence of volatile impurities
is suspected  of  causing  any significant variation in
sampling results, separate investigation of this factor
would be advisable.

      While the exact cause has not been determined,
greater amounts of tarry materials would be expected
if the particulate  sample  contained  a substantial
amount of coal smoke, smoke from an operation such
as a hot mix asphalt plant or coke oven, particulates
from  vehicle exhaust, or other materials that would
likely be high in organic content. Much smaller losses
would be expected in areas where the primary con-
stituents of atmospheric particulates would be natural
soil particles, dust from sandstorms, or other mate-
rials of mineral origin.
    III. COLLABORATIVE TESTING OF
                THE METHOD

     An important step in the standardization of any
method of measurement is the collaborative testing of
a proposed  method to  determine,  on a  statistical
basis, the limits of error which can be expected when
the method  is used by  a typical  group of investiga-
tors. The  collaborative,  or  interlaboratory, test of a
method is an indispensable part of the development
and  standardization  of an analytical  procedure to
insure  that (l)the procedure is  clear and complete,
and  (2) the  procedure does give results whose  pre-
cision and accuracy are in accord with  those claimed
for the method/^) Among other organizations, the
American  Association  of Analytical  Chemists
(AOAC) and the American Society  for Testing and
Materials (ASTM) have  been  active in the field of
collaborative testing and have published guidelines of
the  proper  procedure for conducting collaborative
tests and evaluating the data obtained/^) Publica-
tions  of  both  of these  organizations  were  used
extensively in planning and conducting the collabora-
tive  test  of this  method  to measure atmospheric
particulates.

     After  the  preliminary  evaluation of the  pro-
posed method had been completed and various ques-
tions  regarding  procedure had  been clarified,  a
detailed collaborative  test was undertaken to obtain
the necessary data to make a statistical evaluation of
the method. This section of the  report describes the
test  plan  that  was developed,  presents  the  data
obtained,  and provides  a statistical analysis of the
data, together with conclusions  based  on  the results
and statistical analysis.

A.   Selection of Collaborators
      Since  the  preliminary  evaluation indicated a
possible source of error due  to  loss of weight after
sample collection, this factor was also considered in
conducting  the  collaborative test. The results  are
discussed  subsequently  in   outlining  various con-
siderations which may affect the precision of  the
standard method.
      If a collaborative test is to achieve the desired
objectives, it is necessary that the participants in the
collaborative test be representative of the large group
that will ultimately make  use of the method being
tested.  Since  air  pollution  measurements are   of
interest to many  different groups, it was desirable  to
include in  the group  of collaborators  a  variety  of

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governmental  agencies, universities, industrial labora-
tories, and others. The final selection included three
participants from federal laboratories, five from state
and local air  pollution control agencies, one from
industry,  two from  universities, and  one  from a
research organization. A complete list of the partici-
pants and their affiliation  is given elsewhere in this
report.

      Each laboratory that agreed to participate was
asked to select a staff member with previous experi-
ence  in measuring  particulates  by the high volume
sampler method. This was done to avoid errors that
otherwise would result from lack of experience, and
thus provide  a more  realistic  appraisal  of the  capa-
bility of the  method being tested. Each laboratory
also was engaged in  making  routine measurements
with  this method  or  some variation of the  same
method, and possessed the  necessary equipment for
calibration of  samplers, conditioning and weighing of
filters,  and other  work  necessary to  follow  the
method as outlined.

B.    Planning the Test Series

      Ideally,  a  collaborative  test should  be con-
ducted by a group of participants, each working in his
own  laboratory  in his  usual  manner.  For  some
methods to measure air pollution, this can be accom-
plished by sending known samples to various labora-
tories for analysis. In this case, however, no method
was available to send a "standard atmosphere" which
could be used  for test purposes, and, therefore, it was
necessary to make measurements by sampling a real
atmosphere. In order to assure uniformity, the partic-
ipants  were brought  together  to  one  location to
sample  the  same  atmosphere  simultaneously. A
laboratory building  used by the Air Pollution Control
Office in Cincinnati, Ohio, was selected where a large
area on the roof of a  two-story wing of the  building
provided adequate space. A clear space approximately
SOX 100ft  was  available without obstructions.  An
exhaust fan  outlet on the roof was equipped with a
duct which  discharged the exhaust air  down below
roof level along the side of the building so that no
disruption of normal atmospheric turbulence would
occur.  This  location  was  also  convenient  in  that
laboratory  facilities  were  available  in  the  same
building to provide a work area for  calibration and
assembly of equipment.

      The building chosen was located in a neighbor-
hood which contained both residential and industrial
property. Several  industrial plants in the area pro-
duced visible emissions,  although none were located
close enough  to the  site so that a dominant effect
from a single source would be expected. Cincinnati is
also in an area where coal is used extensively as fuel,
and thus some coal smoke would be  included in the
atmospheric particulates present. The  nearest freeway
with heavy traffic was several  hundred yards distant.
By sampling on  top of a two-story wing of the build-
ing, localized effects from  vehicle  traffic in  the
immediate  neighborhood would  be minimized. Thus,
all  preliminary  evidence  indicated that this site was
typical  of many urban locations that might be used
for air pollution monitoring, and would be expected
to give results representative of particulate levels over
a wide  area of that portion of  the city. Subsequent
experience  in the collaborative test appeared to con-
firm this expectation, and, therefore,  the  area of the
test site was considered to be well suited to the objec-
tives of the test.

      In order to minimize  any effects which might
result from working in unfamiliar  surroundings, each
participant was  instructed to calibrate the sampler,
condition and weigh  all filters, and do all other pre-
paratory and followup work in  his own  laboratory.
Work in Cincinnati was then to be limited to recheck-
ing the  flow rate and to  actual  sample collection.
Thus, insofar as  possible, the final results should indi-
cate what each participant routinely accomplishes in
his own laboratory. In the original schedule, time was
allowed for   rechecking  sampler  calibration   in
Cincinnati prior  to sampling, to  be sure that shipping
of equipment had not adversely affected the calibra-
tion. However,  it was found that many  laboratories
did not have access to a  positive displacement meter
to  use as a primary  calibration standard  and other
laboratories did  not  use  the standard type of orifice
meter  for  calibration.  Therefore,   the  entire

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calibration procedure specified in the method was
repeated by all participants after arrival in Cincinnati,
including both the calibration of the orifice  meter
with a  primary  standard and  the calibration of the
sampler with the orifice meter.

C.   Site Evaluation

     In order to be sure that  the site chosen for the
collaborative test was suitable, a preliminary evalua-
tion of this particular site was performed prior  to the
actual test. The primary objective of this work was to
confirm  the fact that all samplers used in the test
would  be sampling the same  atmosphere. For this
purpose, five samplers were placed  in representative
locations on top of the building and were operated
for three sampling periods  of approximately  24 hr
each. While some variation occurred among samplers,
as expected, there was no  systematic pattern  which
would indicate a consistent difference in atmospheric
dust levels. The  data  are shown in Table I and indi-
cate that location within different  sections of the
roof area was essentially immaterial in affecting the
particulate  levels  measured.  Therefore,  when
12 samplers  were  used  simultaneously  during  the
actual test, it  could be assumed that all participants
were measuring the same test atmosphere.

     Another factor considered in evaluation of the
site was  the location  of the 12 samplers, within the
clear space available, when the collaborative test was
conducted.  It was decided  to use two  rows  of
6 samplers  each,  maintaining  a 12-ft  spacing both
ways between samplers.  With this  arrangement, no
sampler was  placed closer to the edge  of the  roof than
12ft, thus avoiding  turbulence and other  flow dis-
turbances that might  exist  at  the edge or  corner of
the building. In the preliminary tests, a 12-ft spacing
was used with 2 of the  5  samplers, and the results
indicated  that no interference resulted. In fact,  a
superficial examination of airflow patterns around a
sampler indicated that any disturbance of airflow was
dissipated rapidly,  and interference with an adjacent
sampler would not be expected unless a spacing of
3 ft or less was used. Therefore, all available evidence
indicated that the site and the proposed arrangement
of samplers were adequate for the purposes of the
test.

D.   Conducting  the Test Series

     Actual  sampling at  the  Cincinnati  site  was
accomplished  in  a single  week  in  October  1970,
from Monday morning to Friday afternoon. Weather
conditions  during the  week  were variable,  covering
the normal range of conditions expected at  that sea-
son of the year.  Light rain fell during portions of the
second and third day.  The morning  period  on Mon-
day was  used by all  participants to unpack  equip-
ment, calibrate orifice  meters and samplers, and set
up shelters. The first  sampling period was started in
the afternoon on Monday when all participants were
ready.

     All samplers  were  started  simultaneously for
the actual sampling  period  and each participant
observed  and  recorded the initial flow rate. At the
end of each sampling period (approximately 24 hr),
each participant determined the final flow  rate and
then all samplers were stopped simultaneously.  The
filters were removed, new filters were installed for the
next sample  period, and  the entire procedure  was
repeated. While the samplers  were running, everyone
stayed away from the  test site  except for occasional
checks of equipment, to minimize errors due to dust
that might be raised by walking  on the roof.
     At  the  conclusion  of the final test period on
Friday, final flow rate figures were obtained, samplers
were  stopped,  the  filters  were  removed  from the
samplers, and shelters and other equipment were pack-
ed for shipment. Each participant  was asked to return
the filters to  his own  laboratory, condition them as
specified  in the method on Monday and Tuesday (for a
total of 24 hr), and then obtain a final weight. This
weight was used for  calculations and, in addition, sub-
sequent weighings were also made  to obtain additional
data on weight loss.  The question of weight loss over a
period of time is  discussed in connection with the
evaluation of the precision of the method.

     One participant lost a sample when the sampler
motor  brushes failed. However, this person replaced

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 the brushes and recalibrated the sampler prior to the
 beginning of the next period, thus limiting the loss to
 a single sample. This gave a total of 47 samples from
 all participants out of a possible 48 (12 participants,
 4  samples  each). Data  from these 47 samples were
 then used for the statistical analysis which was per-
 formed.

 E.   Summary of Statistical Analysis

      The  fundamental  purpose of  the   statistical
 design was  to determine the existence  and amount of
 both random and  systematic laboratory errors. The
 experiment was designed so that, in addition to inter-
 laboratory comparisons, some implications could be
 made  regarding  the day-to-day variations  within an
 individual laboratory. No estimate is  possible, how-
 ever, for  replication errors, since a true replicate can-
 not be accomplished. Since it was impossible  to pre-
 pare  and submit  samples  with known   reference
 values,  no statements  regarding the  accuracy  of the
 method can be made.

      In consideration of the logistics involved, a very
 comprehensive test is not feasible;however, a modest
 test design was possible. The approach was to have all
 collaborators sample from the same real atmosphere
 at  the  same  site  at  the same time.  There were
 12 collaborators, each from  a different laboratory,
 who worked independently but simultaneously at the
 same site  collecting data for 4 consecutive days. Thus,
 each day  constituted a separate sample  or material, of
 unknown  concentration,  but common  to  all
 participants.  It should be made clear that  there was
 no intent to measure  day-to-day variations for the
 site. Neither was it desirable that all days be the same,
 a condition  not  under experimental control. A single
 result was collected by each analyst for each  of the
 4 days,  yielding the data shown in Table II. Samples
 were collected  over a 24-hr interval;  therefore, no
 replication was  possible  for  a  particular  analyst-
 sampler combination. Although the data do  not cover
 a wide range, they are certainly satisfactory. Notice
 that there are  2 days  with means near 120 micro-
 grams  per cubic  meter (jug/m3) and  2 days with
means  significantly lower and near  80 jug/m3,  a
fortuitous but agreeable circumstance.
         TABLE II. COLLABORATIVE TESTING
           DATA-HIGH-VOLUME METHOD
                 FOR PARTICULATES
            Paniculate Concentration, Mg/m3
Laboratory Number
222
311
320
341
345
509
572t{**
575ttt
578t
600
7871
799
Day 1
138
25
28
26
27
28
28
08
26
25
25
131
Day 2
*
80
72
75
78
74
82
73
77
72
76
76
Day 3
87
82
81
83
87
86
84
72
83
80
83
86
Day 4
114
113
112
114
124
121
112
93
1 11
110
117
120
*Missmg data due lo equipment maltunction
T Recalculated results because of errors m units ot measurement
I Recalculated results because ot arithmetic errors
**Recalculated results because ot ncorrect data entry tor time of
sampling
ttRecalculated results because ot errors in calibration curves
      The  statistical analysis, presented in more detail
 in  Appendix B, is  summarized  in  the  following
 paragraphs.

      The  standard deviation for each day fluctuated
 systematically  with the  respective means,  indicating
 that it was advisable that the data be  transformed to a
 different scale. The  appropriate tests were applied,
 resulting in the use of the simple logarithmic trans-
 formation.  All subsequent  analyses were  made on
 transformed data.

      The missing sample for one laboratory required
 either that all data  for that laboratory be rejected or
 that  an  appropriate  substitution  be made for  the
 missing value.  The  latter approach was followed, as
 outlined in Appendix B.

      Following  standardized  procedures  for  the
 analysis of data of this type, Figure  1 was  prepared.
 This  illustration is  based on  transformed  data and
 shows a separate line for each laboratory, plotting the
 observed values against reference values equal  to the
 mean of   all  laboratories  for each day. This
 makes it possible  to visualize  the grouping of the
 data  and  to identify  the  variation  between
 laboratories.   One  obvious  advantage  of  this
 presentation  is that  any  outliers   can  be  easily
identified;  in  this  case, it  is  obvious  that  the
results  of Laboratory  575   are  significantly  dif-
ferent. Other  outlier tests also substantiated  this

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   2.20
   2.15
   1.80
     1.85    1.90   1.95   2.00    2.05   2.10    2.15
                     Reference Value

    FIGURE 1. GRAPHIC DATA SUMMARY FOR ALL
      LABORATORIES, LOGARITHMIC DATA
                TRANSFORMATION
conclusion,  and  the  final  statistical  analysis  was
made omitting Laboratory 575.

     An analysis of variance of the transformed data
for 11 laboratories was  made, and the model  and
more detailed data are given in Appendix B. The ulti-
mate purpose for making the analysis of variance is to
derive components of variance which are shown in
Table III.  The mean square from the deviation from
linear term is the component V(d) which contains the
unknown  replication error plus the irreducible experi-
mental error of the method. Components V(u)  and
V(b) express the variability  of the means  and  the

      TABLE HI. COMPONENTS OF VARIANCE
Component
V(u)
V(b)
V(d)
Value*
0.000087
0
0.000166
Percent
of Total
34
66
Significance
>99%
<50%
Relative Deviation,
Percent
Estimate
-i i
0
30
Confidencet
Interval
06 to 4 3
0 to 1 4
2 3 to 4 4
*Based on transformed data
f95 percent confidence interval
slopes, respectively, from one laboratory to another.
These  components  were  calculated  according to
recommended practice.^) A negative value for V(b)
was obtained and  therefore replaced with a value of
zero, since negative variances are meaningless. V(u) is
highly  significant while V(b), of course, is not signifi-
cant. The  confidence intervals (95 percent level of
significance)  for  each  component  are   shown  in
Table III. Since the component V(b) is not significant
at the  95 percent level of significance, the lower con-
fidence limit is naturally zero.

     The  quantities V(d),  V(u),  and V(b) are the
basic elements from which the precision of  the results
can be estimated  for any set of conditions.'^) The
reproducibility and the repeatability(8) may thus be
determined.

     Two-thirds of the variance is accounted for by
the component V(d). The relative  standard deviation
for a single material analyzed repeatedly in the same
laboratory by  the same analyst  is  3.0 percent, the
repeatability  of the method.  Any two such values
should be considered suspect (95 percent confidence
level)  if they differ by more than 4.3 percent.  Con-
versely,  two  materials analyzed in the same labora-
tory may  not be considered significantly different if
the results differ by less than 4.3 percent.

      One-third of the  variance is accounted  for by
the component V(u). The relative  standard deviation
for a single material analyzed in different laboratories
is 3.7 percent,  the  reproducibility  of the method.
Any two  such  values should be  considered suspect
(95 percent confidence  level) if they differ by more
than   5.3 percent.  Conversely,  two materials, one
analyzed in each of two laboratories, may not be con-
sidered  to be significantly different if the  results
differ  by less than 5.3 percent.

       Some additional information was obtained dur-
ing  the  collaborative  test relating  to  errors  from
individual steps within the method. Each collaborator
was asked to submit the results of a series of weights
of the filters that were supplied. A senes of  three
weights  at 24-hr intervals  was requested for each of

-------
 ten filters provided. These data were obtained by the
 collaborator prior to coming to the test site. Follow-
 ing  the  formal  collaborative  test,  each  analyst
 returned to his own laboratory and made a series of
 four weights,  at 24-hr intervals, of each of the  ten
 filters, not all of which were used in the test. The
 weight after the  first 24-hr equilibration was used, as
 specified by the method, to calculate the total sus-
 pended   particulate  concentrations  which  were
 reported.

      The supplementary weight data for the succeed-
 ing 3 days are useful for two purposes: first, to pro-
 vide  an estimate  of a limit of  detectability of  the
 method;  and,  second,  to give an  indication of  the
 stability of the suspended particulate matter.

      These data can be divided into three subsets:

      •     Unexposed filters prior  to test period

      •     Unexposed filters after test period

      •     Exposed filters used in the test.

 These data indicate the combined  random effects of
 equilibration, weighing, and decomposition or volatil-
 ization of particulate matter. The standard deviation
 of  the weights for each of the cases is 0.7, 0.9, and
 1.7 mg, respectively. The  number of sets of replicates
 for  each  case  is  100,  56, and  43,  respectively.
 Bartlett's test(ll) for homogeneity of variances leads
 to the acceptance of the null hypothesis that  there is
 no  difference between the variances in the weights of
 the unexposed  filters before and after the test period.
 The variance in the weights of the used filters was
 shown to  be significantly greater  than that of the
 unexposed filters, indicating  that there are significant
 changes in  the weights of  exposed filters  over the
 96-hr period.

      The data, which are too voluminous to report
here,  show weight losses up to 10 mg, or about 5 per-
 cent,  for  an individual  used filter over the 4-day
period of equilibration. This loss,  though less  than
 that indicated in  the preliminary work, is significant
 in terms of the  precision data reported above. This
 illustrates the  importance  of  careful control and
 uniformity of equilibration in order to achieve satis-
 factory  reproducibility.  The  presence of volatile
 materials can cause unpredictable errors.

      In the absence of significant amounts of volatile
 material, an estimate of the lower detection limit can
 be made. The standard deviation of the difference in
 the mean weights of the unexposed filters before and
 after the test period  could be directly determined for
 a set of 56 observations. The  result obtained was
 1.5 mg,  which is almost exactly  the  same  value
 obtained by the less direct  method  of doubling the
 standard  deviation obtained for all unexposed filter
 weights. Based upon this  result, the 95 percent con-
 fidence limit for  these differences is  3.0 mg.  There-
 fore, a difference in weight of 3 mg or less cannot be
 considered  to be significantly  different from zero.
 The  minimum  detectable  amount  of  particulate
 matter  is  thus 3 mg,  and, for a 24-hr  sample  at
 1.5 cubic meters  per minute  (53 cfm), this  would
 correspond  to a minimum detectable  concentration
 of 1.4 ;Ug/m3. A concentration this low will  rarely, if
 ever,  be observed in the atmosphere.

 F.   Calibration Errors

      It was possible  to investigate the random error
 associated  with the calibration  of the orifice units
 with  the  primary  standard positive  displacement
 meter.  The  experimental  design  was  such that  a
 participant was randomly assigned one of six  identical
 orifice calibration units and one of five  essentially
 identical positive  displacement  meters. The partici-
 pant  then calibrated the orifice  unit according to the
 tentative  method. These  independent calibration
 curves have  been superimposed in Figure 2 which is a
 log-log plot of the flow rate through the orifice  versus
 the pressure  differential across  the orifice. With the
 exception of one  laboratory (787) and one atypical
 point for another laboratory (311), linear results were
obtained.  Another laboratory (572) switched primary
standard meters in the middle of the  calibration pro-
cedure;  however,  there  were  no noticeable irregu-
larities  in its results.  A  least squares  regression

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   15



   12


   10

S  9

I  8

!  7
<0
o
f  6
oT
£
?  5
  a
  o
     1.5
                           Least Squares Line
                           95% Confidence Limits
       0.6  0.7 0.8 0.9 1.0   1.2
                                 1.5
                                        2.0   2.3
           Flow Rate Through Positive Displacement
                      Meter, m^/min.
   FIGURE 2. ORIFICE METER CALIBRATION DATA


analysis was made (omitting Laboratory 787 and the
extraneous  point of Laboratory 311) and the line of
best  fit is shown in Figure 2. The magnitude of the
derived constants for the regression line is of second-
ary importance. The important consideration is the
standard error of estimate which is 2.1 percent. This
error combines the errors  from  variation  among
orifice units, variation among  positive displacement
meters, and experimental measurement in the calibra-
tion  procedure. The 95 percent confidence interval
for the error associated with calibration is ±4.1 per-
cent. All the orifice units used in the test were new
and in good condition.


      The  manufacture^12) furnishes  an "Average
Calibration Curve" with each orifice. The orifice units
are quoted  as being accurate to ±1.0 percent. These
calibration data are almost identical with the line of
                                                    best fit in Figure 2. The temperature and pressure
                                                    conditions are approximately the same for each.


                                                          It should not be concluded that the calibration
                                                    of the orifice should be omitted on the basis of these
                                                    estimates; rather, that  the main purpose of periodic
                                                    orifice calibration is to  provide assurance that  the
                                                    orifice has not been damaged or otherwise changed in
                                                    accuracy. A difference of more than 4 percent from
                                                    the  manufacturer's curve probably means that  the
                                                    orifice has been damaged.
                                                                LIST OF REFERENCES
                                                    1.    Lynam,  D. R.,  Pierce, J. O., and  Cholak, J.,
                                                         "Calibration of the High-Volume Air Sampler,"
                                                         American  Industrial  Hygiene  Association
                                                         Journal,  No. 30, pp 83-88  (January-February
                                                         1969).

                                                    2.    Unpublished data,  Southwest Research  Insti-
                                                         tute, Houston, Texas.

                                                    3.    Unpublished data,  Texas Air Control Board,
                                                         Austin, Texas.

                                                    4.    Unpublished data, Air Pollution Control Pro-
                                                         gram,  City of  Houston Health Department,
                                                         Houston, Texas.

                                                    5.    Youden, W.  J.,  "The Collaborative  Test,"
                                                         Journal of the AOAC, Vol 46, No. 1, pp  55-62
                                                         (1963).

                                                    6.    Handbook  of  the  AOAC, Second Edition,
                                                         October 1, 1966.

                                                    7.    ASTM Manual for Conducting an Interlabora-
                                                         tory Study  of a  Test Method, ASTM STP
                                                         No. 335, Am. Soc. Testing & Mats. (1963).

                                                    8.    Recommended  Practice for Developing  Preci-
                                                         sion Data  on ASTM  Methods for Analysis and
                                                         Testing of Industrial Chemicals, ASTM Designa-
                                                         tion: El80-67. 1968 Book of ASTM Standards,
                                                         Part 30.

                                                    9.    ASTM STP No. 335, op. cit., p 37.

                                                    10.  Ibid, pp 37-40.

                                                    11.  Dixon,  Wilfred J.,  and Massey, Frank!., Jr.,
                                                         Introduction  to  Statistical  Analysis,  Chap-
                                                         ter 10,  pp 179-180,  McGraw-Hill Book Com-
                                                         pany, Inc., New York (1957).

                                                    12.  General Metals Works, Cleves, Ohio.
                                                  10

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                                               RULES AND  REGULATIONS
                                                                                                                       8191
                                                     APPENDIX A

                        REFERENCE  METHOD FOR THE  DETERMINATION  OF
                          SUSPENDED PARTICULATES IN THE ATMOSPHERE
                                            (HIGH VOLUME METHOD)
                       Reproduced  from  Appendix  B,  "National  Primary  and  Secondary
                       Ambient Air Standards," Federal Register, Vol  36, No.  84, Part  II,
                       Friday,  April 30,  1971.
 APPENDIX  B—REFERENCE  METHOD FOR  THE
  DETERMINATION OF SUSPENDED PAHTICULATES
  IN   THE  ATMOSPHERE   (HIGH  VOLUME
  METHOD)

  1. Principle and Applicability.
  1.1  Air  Is drawn into a covered housing
and through a niter by means of a high-flow-
rate blower at a flow  rate (1.13 to 1.70 m.5/
min.;  40 to 60  ft.'/min.) that allows sus-
pended  particles having diameters of less
than 100 ion.  (Stokes equivalent diameter)
to pass to the  filter  surface.  (I)  Particles
within the size range of 100 to O.ljim. diame-
ter are ordinarily collected on glass fiber fil-
ters.  The mass concentration of suspended
particulates in the  ambient air (/tg./m.s) is
computed by measuring the mass of collected
particulates and the volume of  air sampled.

  1 2  This method Is applicable to measure-
ment of the mass concentration of suspended
particulates in ambient air. The size of the.
sample  collected is  usually adequate  for
other  analyses.
  2. Range and Sensitivity,
  2 1  When the sampler is operated  at an
average flow rate of  1.70 m.Vmin. (60 ft.V
mm.)  for 24 hours, an adequate sample will
be obtained even in  an atmosphere having
concentrations of suspended particulates as
low as  1  /ig./mA If  particulate levels  are
unusually  high, a satisfactory sample may be
obtained in 6 to 8  hours or less. For deter-
mination of average  concentrations ol sus-
pended particulates in ambient  air, a stand-
ard  sampling  period   of  24  hours  is
recommended.

  2.3  Weights are  determined  to the near-
est milligram, airflow  rates are determined to
the nearest 0.03 m.Vmin. (1.0  ft.'/mln.),
times  are  determined to  the  nearest  2
 minutes, and mass concentrations  are  re-
 ported to the nearest mlcrogram per cubic
 meter. •
  3.~ Interferences.
  3.1   Partdculate matter that Is oily, such
 as photochemloal «nnng or wood smoke, may
 block the filter »nd cause  a rapid drop in
 airflow at a nonunlform rate. Dense fog or
 high humidity can cause the fitter to become
 too wet and severely reduce the  airflow
 through the filter.
  3.2   Glass-fiber filters  are comparatively
 Insensitive to changes in relative humidity,
 but  collected particulates   can be  hygro-
 scopic. (2)
  4. Precision, Accuracy, and Stability.
  4.1  Based upon collaborative testing, the
 relative standard deviation  (coefficient  of
 variation) for single analyst variation (re-
 peatability of the method)  is  3.0 percent.
 The corresponding value for multilaboratory
 variation (reproduclbillty of  the method) is
3.7 percent. (3)
  4.2  The accuracy with which the sampler
 measures  the true average concentration
 depends upon the constancy of the airflow
 rate through the sampler. The airflow rate Is
 affected by the concentration and the nature
 of the dust in the atmosphere. Under these
 conditions the error in the measured aver-
 age concentration may be in excess of ±50
 percent of the true average concentration, de-
 pending on the amount of reduction of air-
 flow rate and on  the variation of the mass
 concentration of dust with  time during the
 24-hour sampling  period. (4)
  5. Apparatus.
  5.1  Sampling.
  5.1.1 Sampler.  The  sampler consists  of
three  units:  (1)  the faceplate and  gasket,
 (2) the filter adapter assembly, and  (3)  the
 motor  unit. Figure  Bl shows an exploded
 view of these parts, their relationship to each
other,  and how they  are  assembled.  The
sampler must be capable of passing environ-
mental  air through  a  406.5 cm.2  (63 In.8)
portion of a clean 20.3  by 25.4 cm.  (8- by
10-in.) glass-fiber filter at a rate of at least
1.70 m.Vmin. (60 ft.Vmin.). The motor must
be capable of  continuous operation for 24-
hour  periods  with  input  voltages  ranging
from 110 to 120 volts, 50-60 cycles  alternat-
ing current and must have third-wire safety
ground. The  housing lor the  motor unit
may be of any convenient  construction so
long -as the unit remains airtight and leak-
free. The life  of the sampler  motor can be
extended by lowering the voltage by about
10 percent with  a small  "buck or boost"
transformer between the sampler and power
outlet.
  5.1 2  Sampler  Shelter.  It  is important
that the sampler be properly  installed In a
suitable shelter. The shelter is subjected to
extremes of temperature, humidity, and all
types  of air pollutants. For  these reasons
the materials of the shelter must be chosen
carefully. Properly painted exterior plywood
or heavy gauge  aluminum  serve well.  The
sampler must  be mounted vertically in the
shelter so that the glass-fiber filter  is paral-
lel with the ground. The shelter  nrnst be
provided with a roof so that the filter is pro-
tected  from precipitation  and  debris.  The
internal arrangement and configuration of
a suitable shelter with a gable roof are shown
in Figure B2. The clearance area between the
main  housing and the roof  at Its closest
point should  be  580 5± 193.5  cm.!  (90±30
In =). The main housing should be rectangu-
lar, with dimensions of  about  29 by 36 cm.
(ll'/2  by 14 in.).
  513  Rotameter.   Marked  in   arbitrary
units,  frequently 0 to 70,  and capable of
being calibrated. Other  devices of  at least
comparable accuracy may be  used.
                                  FEDERAL  REGISTER, VOL.  36, NO. 84—FRIDAY, APRIL 30, 1971
                                                        A-l

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8192
      RULES  AND  REGULATIONS
  6.1.4  Orifice Calibration  Unit. Consisting
of a metal tube 7.6'cm. (3  in.)  ID and 15.9
cm.  (6% In.) long with a static pressure tap
5.1  cm.  (2  in.) from one  end. See  Figure
B3. The tube end nearest the pressure tap is
flanged to about 10.8 cm. (4% in.)  OD with
a male thread of the same  size  as  the Inlet
end of the high-volume air sampler. A single
metal plate 9.2 cm.  (3% in.) in diameter and
0.24  cm.  (%2 in.) thick with a central orifice
2.9 cm. (1% in.) in diameter is held in place
at the air Inlet end with a  female  threaded
ring. The other end of the tube is flanged to
hold a loose female  threaded coupling, which
screws onto the inlet of the sampler. An 18-
hole metal plate, an Integral part of the unit,
is positioned between the orifice and sampler
to simulate the resistance of  a  clean glass-
fiber  filter.  An orifice  calibration unit is
shown in Figure B3.
  5.1.5  Differential Manometer. Capable of
measuring  to at least  40  cm.  (16 in.)  of
water.
  5.1.6  Positive Displacement Meter. Cali-
brated in cubic meters  or cubic feet, to be
used as a primary standard.
  5.1.7  Barometer. Capable  of measuring at-
mospheric pressure  to the nearest mm.
  5.2 Analysis.
  5.2.1  Filter  Conditioning  Environment.
Balance  room or desiccator maintained  at
15° to 35°C. and less than 50 percent relative
humidity.
  5.2.2  Analytical  Balance. Equipped with
a weighing chamber designed to handle un-'
folded 20.3 by 25.4  cm.  (8- by 10-in.) filters
and  having  a sensitivity of  0.1 rog.
  5.2.3  Light Source. Frequently a table of
the type used to view X-ray  films.
  5.2.4  Numbering Device. Capable of print-
ing identification numbers on the filters.
  6.  Reagents.
  6.1 Filter Media. Glass-fiber filters having
a collection efficiency of at  least 99 percent
for particles of 0.3 um. diameter, as measured
by the DOP test, are suitable for the quanti-
tative measurement of concentrations of sus-
pended particulates, (5)  although some other
medium, such as paper,  may be desirable for
some analyses. If a  more detailed analysis is
contemplated, care  must be exercised  to use
filters that contain  low  background concen-
trations of the pollutant being investigated.
Careful  quality control is required to deter-
mine background values of these pollutants.
  7.  Procedure.
  11 Sampling.
  7.1 1  Filter Preparation. Expose each filter
to the light  source and inspect for pinholes,
particles, or other imperfections. Filters with
visible imperfections should not be used. A
small brush is useful  for removing particles.
Equilibrate the filters in the filter condition-
ing environment for 24  hours. Weigh the
niters to the nearest  milligram;  record tare
weight and  filter identification number.  Do
not bend or fold the  filter before collection
of the sample.
  712  Sample Collection. Open the shelter,
loosen the wing nuts, and remove the face-
plate from the  filter holder. Install a num-
bered, preweighed, glass-fiber filter in posi-
tion  (rough side up), replace the faceplate
without  disturbing the  filter,  and  fasten
securely. Undertightening will allow air leak-
age, overtlghtening  will  damage the sponge-
rubber faceplate gasket. A very light applica-
tion  of talcum  powder may be used on the
sponge-rubber faceplate gasket  to prevent
the filter from sticking.  During inclement
weather the sampler  may be  removed to a
protected area  for  filter  change. Close the
roof of the shelter, run the sampler for about
5 minutes,  connect the  rotameter to the
nipple on the back  of the sampler, and read
the rotameter ball with rotameter in a verti-
cal position. Estimate to  the nearest whole
number.  If  the ball  is  fluctuating rapidly,
tip the  rotameter and slowly straighten it
until the ball gives a constant reading. Dis-
connect the rotameter from the nipple; re-
cord the initial rotameter reading and the
starting time and date on the filter folder.
(The rotameter should never  be connected
to the sampler except when the flow is being
measured.) Sample for 24 hours from mid-
night to midnight and take a final rotameter
reading. Record the final rotameter reading
and ending time and date on the filter folder.
Remove the faceplate as described above and
carefully remove the filter from the holder,
touching only thevouter edges. Fold  the filter
lengthwise so that only surfaces with col-
lected particulates are In contact, and place
In a manlla folder. Record on the folder the
filter number, location, and any other factors,
such as meteorological conditions or razing
of nearby buildings, that might affect the
results. If the sample is defective, void it at
this time. In order to obtain a valid sample,
the high-volume sampler must be  operated
with  the  same  rotameter and  tubing that
were used during its calibration.
  7.2   Analysis.  Equilibrate the exposed fil-
ters for 24 hours in the  filter conditioning
environment,  then reweigh. After  they are
weighed, the filters may be saved for detailed
chemical analysis.
  7.3   Maintenance.
  7.3.1  Sampler  Motor.  Replace  brushes
before they  are  worn to  the point where
motor damage can occur.
  7.3.2  Faceplate Gasket. Replace when the
margins of samples are no longer sharp. The
gasket may be sealed to the faceplate with
rubber cement or double-sided adhesive tape.
  7.3 3  Rotameter. Clean as required, using
alcohol.
  8. Calibration.
  8.1   Purpose. Since  only  a small portion
of the total air sampled passes through the
rotameter during measurement,  the rotam-
eter must be  calibrated  against actual air-
flow with the orifice calibration unit. Before
the orifice calibration unit can  be used to
calibrate the rotameter,  the orifice calibra-
tion unit Itself must  be  calibrated against
the positive displacement primary standard.
  8 1.1  Orifice Calibration Unit. Attach the
orifice calibration unit to  the  intake end
of the positive displacement primary  stand-
ard and attach a high-volume motor blower
unit to  the  exhaust  end  of  the  primary
standard.  Connect one end  of  a differential
manometer to the differential pressure tap
of the orifice calibration unit and leave the
other end open to the atmosphere. Operate
the high-volume motor blower unit so that
a series of different, but constant, airflows
(usually  six)  are obtained for  definite time
periods. Record the reading on the  differen-
tial manometer at each airflow. The  different
constant airflows are obtained by placing a
series of  loadplates,  one  at a time,  between
the calibration unit and the primary stand-
ard. Placing the orifice before  the  inlet re-
duces the pressure at the inlet of the primary
standard  below  atmospheric;  therefore, a
correction must be made for the increase in
volume caused by this decreased inlet pres-
sure. Attach one end of a second differential
manameter to an inlet pressure tap  of the
primary standard and leave the  other open
to the atmosphere. During each of  the con-
stant  airflow measurements  made  above,
measure  the  true  inlet pressure  of the
primary standard with this  second  differen-
tial manometer. Measure  atmospheric pres-
sure and temperature. Correct the measured
air  volume to true air volume as directed in
9.1.1,  then obtain true  airflow rate,  Q,  as
directed in 9.1.3. Plot the differential manom-
eter readings of the orifice unit versus Q.
  8.1.2  High-Volume  Sampler. Assemble a
high-volume  sampler with a clean filter in
place and run for at least 5 minutes. Attach
a rotameter, read the ball, adjust so that the
ball reads 65,  and seal the adjusting mech-
anism so that it cannot  be changed easily.
Shut off motor, remove the filter, and attach
the orifice calibration  unlit in its place. Op-
erate the high-volume sampler at a series of
different, but constant, airflows (usually six) .
Record the reading of the differential  ma-
nometer on the orifice calibration unit, and
record the readings of  the rotameter at each
flow. Measure atmospheric pressure  and tem-
perature. Convert the differential manometer
reading to m.'/min., Q, then plot rotameter
reading versus  Q.
  8.1.3  Correction for Differences in Pressure
or Temperature. See Addendum B.
  9.  Calculations.
  9.1  Calibration of Orifice.
  9.1.1  True Air Volume. Calculate the air
volume measured  by  the positive  displace-
ment primary standard.

                 (P.-Pm)
            Va= - (VM)
                    P.
   V»=True air volume at atmospheric pres-
 —       sure, m.3
   P. = Barometric pressure, mm. Hg.
  Pn = Pressure drop  ait  inlet  of  primary
         standard, mm. Hg.
  VM=Volume measured  by primary stand-
         ard, m.s
  9.1.2  Conversion Factors.
  Inches Hg.X25.4=mm. Hg.
  Inohee water X 73 .48 X 10-" = inches Hg.
  Cubic feet air x 0.0284 = cubic meters air.
  9'.1.3  True Airflow Rate.
                      V.
                  Q=—
                      T

  Q=Plow rate, m.Vmin.
  T=Time of flow, min.

  9.2  Sample Volume.
  9.2.1  Volume Conversion. Convert the ini-
tial  and  final rotameter readings to  true
airflow  rate, Q, using calibration  curve of
81.2.
  9.2.2  Calculate volume of air sampled

                   QiQi
               V=- - XT
                    2
   V — Air volume sampled, m.3
  Qi = Initial airflow rate, m.Vmin.
  Qt = Final airflow rate, m.Vmin.
   T= Sampling time, min.
  9.3   Calculate mass  concentration of sus-
pended particulates
           SP =
                    i-Wi) xlO«
  S.P.^Mass  concentration  of  suspended
          particulates, /tg/m.s
   Wi = Initial weight of filter, g.
   Wt = Final weight of filter, g.
    V = Air volume sampled, m.3
   10G — Conversion of g. to fig.
  10. References.
(1) Robson,  C.  D.,   and   Foster,   K.  E.,
      "Evaluation of Air Particulate Sam-
      pling  Equipment",   Am.  Ind.  Hyg.
      Assoc. J. 24, 404 (1962).
(2) Tierney,  G.  P.,  and   Conner,   W.  D.,
      "Hygroscopic Effects on Weight Deter-
      minations of  Particulates  Collected on
      Glass-Fiber  Filters",   Am.  Ind.  Hyg.
      Assoc. J. 28, 363 (1967).
(3) Unpublished data based on a collabora-
      tive  test involving   12 participants,
      conducted under the direction of the
      Methods Standardization Services Sec-
      tion of the National Air Pollution Con-
      trol Administration, October, 1970.
(4) 'Harrison, W. K.,  Nader, J. S., and  Fug-
      man, P. S., "Constant Flow Regulators
      for High-Volume  Air Sampler", Am.
      Ind. Hyg. Assoc. J. 21, 114-120  (1960).
                                    FEDERAL REGISTER, VOL. 36, NO.  84—FRIDAY, APRIL 30,  1971
                                                                     A-2

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                                              RULES AND  REGULATIONS
                                                                                                                          8193
                   (5) Pate, J. B., and Tabor, E. C., "Analytical
                        Aspects of the Use of Glass-Fiber Fil-
                        ters for the Collection and Analysis of
                        Atmospheric Partlculate Matter", Am.
                        Ind. Hyg. Assoc. J. 23. 144-150  (1962).
                                   ADDENDA

                    A. Alternative Equipment.
                    A modification of the high-volume sampler
                  Incorporating  a method for  recording the
                  actual airflow over the  entire sampling pe-
                  riod has been  described, and Is acceptable
                  for measuring  the  concentration of  sus-
                  pended partlculates (Hendefson, J. S., Eighth
                  Conference on Methods In Air Pollution and
                  Industrial Hygiene  Studies,  1967,  Oakland,
                  Calif.). This modification consists of an ex-
                  haust  orifice   meter  assembly  connected
                  through  a transducer  to a  system for  con-
                  tinuously recording  airflow  on a circular
                  chart. The volume of air  sampled  is  cal-
                  culated by the following equation:
                                  V = QXT.
                    Q = Average sampling rate, m.Ymin.
                    T = Sampling time, minutes.
                  The average sampling rate, Q, is determined
                  from the recorder chart by estimation If the
                  flow rate does  not vary more than 0.11  m.V
                  min.  (4  ft.Vmin ) during the sampling pe-
                  riod. If  the flow rate  does  vary more  than
                  0.11 m.3  (4 ft.Vmin.)  during the sampling
                  period, read the  flow  rate  from the chart
                  at 2-hour Intervals and  take the average.
                    B. Pressure and Temperature Corrections.
  If  the  pressure or  temperature  during
high-volume sampler calibration is substan-
tially different from the pressure or tempera-
ture during orifice calibration, a correction
of the flow rate, Q, may be required. If the
pressures  differ by no more than 15 percent
and the temperatures differ by no more than
100  percent   (°C),  the error  In  the  uu-
corrected  flow-rate will be no more than 15
percent. If necessary,  obtain the  corrected
flow rate  as directed below.  This correction
applies only to orifice meters having a con-
stant orifice  coefficient. The  coefficient for
the calibrating orifice described in 5.1.4 has
been  shown experimentally to  be  constant
over the normal operating range of the high-
volume sampler  (0.6 to 2.2 m.Vmln.; 20 to 78
ft.Vmin.). Calculate corrected flow rate:
  Q2=Corrected flow rate, m.'/min.
  Q!=FIOW rate during high-volume sampler
        calibration (Section 8.1.2), m.Vmin.
  T!=Absolute temperature  during orlnce
        unit calibration (Section 8.1.1),  'K
        or °R.            ^
  P!=Barometric pressure during orifice unit
        calibration (Section 8.1.1), mm. Hg.
  Ta=Absolute temperature  during high-
        volume sampler calibration (Section
        8.1.2), °Kor 'R.
  Ps = Barometric pressure  during high-vol-
        ume  sampler  calibration  (Section
        8.12), mm. Hg.
                    ADAPTER
                    MOUNTING       MOTOR
                     PLATE  CASKET
                                      Figure B1  Exploded view of typical high-volume air samplei parts,
No. 84—Ft. II-
                               FEDERAL REGISTER,  VOL. 36,  NO. 84—FRIDAY,  AFKIL 30, 1971
                                                            A-3

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8194
RULES AND REGULATIONS
                   Figure B2. Assembled sampler and shelter.
     ORIFICE
                                           RESISTANCE PLATES
                    Figure B3. Orifice calibration unit.
          FEDERAL REGISTER, VOL. 36,  NO.  84—FRIDAY, APRIL 30, 1971
                                     A-4

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                                            APPENDIX B
                                     STATISTICAL METHODS
1.    Data Transformation

      The total  suspended particulate  measurement
has  often been assumed  to be log-normally distri-
buted. This  is generally advisable whenever the stan-
dard deviation tends to fluctuate systematically with
its  respective  mean. The simple logarithmic trans-
formation is widely applicable but not necessarily the
only one to use.

      Bartlett's testO)* for homogeneity of variance
was  applied  to both transformed and raw data. The
null  hypothesis  that the variances for  each day are
homogeneous was rejected (95 percent level of signifi-
cance) for the full  set  of raw data and accepted for
the full  set  of transformed data. Therefore, in per-
forming  the analysis of variance and all  subsequent
analyses, the  logarithms  (base 10)  of  the  total
suspended particulate measurements were used, since
they can be  assumed to be normally distributed. The
transformed data are shown in Table B-I.

2.    Missing Data

      Missing data in the analysis of variance always
pose a problem, but, fortunately, there  was only one
data gap and  a  simple  approach was  possible. The

      TABLE B-I. SUMMARY OF DATA FOR ALL
       LABORATORIES, WITH LOGARITHMIC
                TRANSFORMATION
Laboratory
Code Number
222
311
320
341
345
509
572
575
578
600
787
799
Mean
Maximum
Minimum
Standard Deviation
	
Day 1
2 1399
20969
2 1072
2 1004
2 1038
2 1072
2 1072
20334
2 1004
20969
20969
2 1173
21006
21399
20334
00243
	
Day 2
9138*
9031
8573
8751
8921
8692
9138
8633
8865
8573
8808
1 8808
1 8828
1 9138
1 8573
00199
Day3
1 9395
1 9138
19085
1 9191
1 9395
1 9345
1 9243
8573
9191
9031
9191
9345
1 9177
1 9395
1 8573
00224
	
Day 4
20569
20531
20492
20569
20934
20828
20492
1 9685
20453
20414
20682
20792
20537
20934
1 9685
00314
Mean
20125
1 9917
1 9806
1 9879
20072
1 9984
1 9986
1 9306
1 9878
19747
1 9912
20029
1 9887
20125
1 9306
00212
Standard
Deviation
0 1053
00979
0 1171
0 1078
0 1074
01151
00950
00854
01016
01130
01072
0 1133

0 1171
00854

*Data value substituted for missing data
method(2) consists of inserting an estimate of the
missing  observation,  so  chosen  to  minimize  the
residual variance. The inserted value makes no contri-
bution to the residual sum of squares, and it is un-
likely to have any serious effect on the conclusions.
Application of the method yielded an estimate equiv-
alent to approximately 82 /ug/m3, but it should be
emphasized that this  value  does  not represent  an
observation. It allows an approximation of the results
obtained by a less powerful nonorthogonal analysis of
the incomplete data.

3.    Linear Model Analysis

      This  experiment is an  illustrative  example of
the nonavailability of known reference values. There
is  no knowledge of the true values for each of the
materials (days). The alternate approach^ >4) is to use
the mean of all laboratories  for each  day to replace
the unknown reference values. These reference values
may be  seen  in Table B-I. The assumption is made
that systematic differences exist between sets of mea-
surements  made by  the  same observer at different
times, and  that these systematic differences are linear
functions of the magnitude of the measurements.
Hence, the scheme is called "the linear model." The
linear model leads to a simple design, but requires a
special method  of statistical  analysis, geared to  the
practical objectives of a collaborative test.

      For each day, we may plot the measured values
versus the  reference value substitutes. The  measured
values should be a linear function  of the  reference
values (all data normally distributed), and the points
corresponding to each line may be  represented by
three parameters: a  mean; a  slope; and a quantity
related to the deviation from linearity, the standard
error of estimate. These parameters are  determined
by a least squares regression analysis. These results for
the transformed data  are shown in Table B-II which
*Superscnpt numbers in parentheses refer to the List of References at the end of this Appendix.
                                                  B-l

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    TABLE B-II.  ESTIMATES OF THE PARAMETERS
      OF THE STRAIGHT LINES CORRESPONDING
      TO THE VARIOUS LABORATORIES, LOGA-
         RITHMIC DATA TRANSFORMATION,
                ALL LABORATORIES
Laboratory
Code Number
222
311
320
341
345
509
572
575
578
600
787
799
Mean
Maximum
Minimum
Mean
2.0125
1.9917
1 .9806
1.9879
2.0072
1.9984
1 .9986
1.9306
1.9878
1.9747
1.9912
2.0029
1 .9887
2.0125
1.9306
Slope
0.9929
0.9294
1.1150
1.0272
1.0122
1.0869
0.8998
0.7966
0.9678
1.0762
1.0193
1.0768
1.0000
1.1150
0.7966
Standard Error of
Estimate
0.0189
0.0110
0.0069
0.0047
0.0197
0.0191
0.0131
0.0218
0.0049
0.0049
0.0098
0.0102
0.0141*
0.0218
0.0047
•Pooled Estimate
was used  to  prepare Figure 1 found in Section III-E
of this report. This figure shows the data for Labora-
tory 575  to  be  notably different from the other
laboratories.

     Control limits for the means and for the slopes
may be computed, based upon the pooled estimate of
standard error. Control charts, in standard deviation
units, for these parameters are shown in Figures B-l
and  B-2.  No control  limits  are  possible for the
  CONTROL CHART FOR MEANS IN SIGMA UNITS

     (WITH LOG TRANSFORMATION)

  STD. ERROR BASED ON DEVIATION FROM LINEARITY     0.007063
         8S2 311  3£0 341 3^5  509 572  575  578 600  767 799
 LAB MS. 575 
-------
    OF SL0PES fY> VS MEWJS (X)

    CWITH LOG TRANSF3HMATI0N>
 C1KHELATION C3EF.
 SLOPE
 INTERCLPT
 0.50050
 2.14690
-3.26951
        - Laboratory 575
  FIGURE B-4. COMPUTER PLOT OF SLOPES VERSUS
           MEANS, ALL LABORATORIES

Although the  individual  data for each  remaining
laboratory are the same as shown in Table B-I, there
are important differences in the summary statistics.
New reference  values have been established, and the
standard deviations are more uniform.

    TABLE B-JII. SUMMARY OF DATA, OMITTING
       LABORATORY 575, WITH LOGARITHMIC
                TRANSFORMATION
Statistic

Mean
Maximum
Minimum
Standard Deviation
Day 1

2 1067
2 1399
20969
00126
Day 2

1 8845
1 9138
1 8573
00199
Day 3

1 9232
1 9395
1 9031
00124
Day 4

20614
20934
20414
00171
Mean

1 9940
20125
1 9747
00113
Standard


0 1171
00950

      Using the new reference values and the remain-
ing 11 laboratories, a  final data  analysis using the
linear model was made. The results of the regression
analysis are shown in Table B-IV, which is analogous
to Table B-II, but  only the individual means are the
same. The slopes and the standard errors of estimate
are more uniform.

     Control limits for the means and for the slopes
may again be computed. The control chart for means
is  not shown because  it is practically the same as
Figure B-l   with the  point for  Laboratory 575
omitted. The  standard error based on deviation from
TABLE B-IV. ESTIMATES OF THE PARAMETERS
 OF THE STRAIGHT LINES CORRESPONDING
     TO THE VARIOUS LABORATORIES,
       OMITTING LABORATORY 575,
           LOGARITHMIC DATA
            TRANSFORMATION
Laboratory
Code Number
222
311
320
341
345
509
572
578
600
787
799
Mean
Maximum
Minimum
•Pooled Estimate
Mean
20125
99 1 7
9806
9879
0072
9984
9980
9878
9747
99 1 2
20029
1 9940
20125
1 9747

Slope
09729
09113
1 0948
1 0089
09955
1 0691
08817
0 9496
1 0566
1 0013
1 0582
1 0000
1 0948
08817

Standard Error ol
Estimate
00205
00124
00063
00028
00181
00170
00149
00064
00047
0 0085
00081
00129*
00205
00028

                                     linearity  is lower and  is 0.006435, which, coupled
                                     with a slightly higher average mean, results in shifting
                                     each point in Figure B-l downward about  0.4 unit.
                                     The control chart for slopes is also not shown because
                                     it is practically the same as Figure B-2 with the point
                                     for Laboratory 575  omitted.  The standard  error
                                     based on deviation from linearity  is lower and is
                                     0.06954, and, of course, the  range of slopes is  sub-
                                     stantially reduced.  The net effect is to  move each
                                     point  in  Figure B-2  downward  approximately
                                     0.2 unit.

                                          The control chart i'or standard errors is similar
                                     in  appearance  to  Figure B-3  with the  point   for
                                     Laboratory 575  omitted,  and, therefore,  is  not
                                     shown. Comparing the standard errors of estimate in
                                     Tables B-1I and B-1V, it can be seen that  the pooled
                                     estimate of standard errors is reduced,  but  that  the
                                     range is approximately  the same after elimination of
                                     Laboratory 575.

                                          The plot of  slopes versus means is shown in
                                     Figure B-5 which is analogous to Figure B-4,  but
                                     indicates  that the deletion of the single atypical point
                                     due  to  Laboratory 575  results  in a  substantial
                                     reduction in the  correlation between the  slopes and
                                     the  means. This is apparent  both visually as well
                                     as  from the correlation coefficients shown  in  Fig-
                                     ures B-4 and B-5.
                                                B-3

-------
    CWITH L0G TRANSF3RMATI3N)

 C0RRELATI0N CHEF*      0.28731
 SLOPE             -I.71JH2
 INTERCEPT           4. 41729
 0.8817-                          *

    1.975   1.981    1.987    1.994   2.000    2.OOF,   J.U1J
  FIGURE B-5.  COMPUTER PLOT OF SLOPES VERSUS
       MEANS, OMITTING LABORATORY 575

     No further elimination of  outliers is required,
and  the  following conclusions can now be drawn:

     •    There is no  significant variation in  the
           means  and  slopes  among the  eleven
           laboratory  lines  which cannot   be
           entirely  explained  by the  scatter due to
           the deviation from linearity.

     •    There is  no  correlation  between  the
           slopes and the  means of the  individual
           lines.
                                                           M,
             = main  effect of laboratory /

             = main  effect of material (day) /'

             = interaction  effect between  labora-
                tory / and  material / and  includes
                unknown replication error

             = 1,  2,  3  . .  . p  =  number  of
                laboratories
                                                                       1,  2,  3  .
                                                                       materials
                             .  . q  =  number  of
                                                      A more  meaningful  analysis  is  obtained  by parti-
                                                      tioning the interaction term as follows:
where  the  first term  is the linear term in which b,
is  the  slope  determined  by the  /th  laboratory,  b
represents the slope of the average total  suspended
particulate  (TSP)  observed-versus-mean  line  (aver-
aged over  all laboratories),  Cj  represents the true
TSP value  for the y'th material, and c  represents
the  true mean  TSP  of all  materials. The  second
term, d,j, is the  deviation from linear  term. The
linear term  indicates  the  difference in slope of the
line  for  a  particular laboratory and the average
slope for all  laboratories, and  the nonlinear term
expresses  the  departures  from  linearity for  this
individual line.
4.   Analysis of Variance

     The general  model  for  the analysis  of the
results,  classified  according to  two criteria,  labora-
tories and materials (simulated by different days),
where
              = an individual measurement
     A       = overall average
      Starting with the ordinary two-factor analysis
of  variance,  the deviation  from  linear component
of  the  interaction  sum  of squares  can be  com-
puted.^)  The sum  of  squares  for  the  linear
component  of  interaction is  then  obtained  by

   TABLE B-V. ANALYSIS OF VARIANCE OMITTING
      LABORATORY 575, WITH LOGARITHMIC
                TRANSFORMATION
Source of Variation
Laboratories
Days
Labs X Days
Linear
Concurrence
Nonconcurrence
Deviation trom Linear
Sum of
Squares
0005126
0 376777
0 004874
0001562
000012')
0001433
0003313
Degree's
ol hreeclom
10

30
11)
1
•I
20
Mean Squaie
I) 0005 1
0 12v5')
000016
000015
1)1)001.'
0000159
0000106
                                                  B-4

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difference.  For  the  sake of  completeness,  the
linear component may be further partitioned into
a  concurrence and  a  nonconcurrence  term,v°)
although it is apparent that no appreciable correla-
tion  exists between the means  and the slopes of
the laboratory lines. This  is done without further
explanation and  is  shown in  Table E-V. The pur-
pose   for  making the  analysis  of variance  is  to
derive  the components  of variance.  These  com-
ponents  are  computed  from  Table B-V  and  are
shown in  Table III in  Section HI-E of this report.
          LIST OF REFERENCES

1.    Dixon, Wilfrid J. and Massey, Frank J., Jr.,
     Introduction  to  Statistical  Analysis,  Chap-
     ter 10,  McGraw-Hill  Book  Company,  Inc.,
     New York, pp 179-180 (1957).
Bennett,  Carl  A. and  Franklin,  Norman L.,
Statistical  Analysis  in Chemistry  and  the
Chemical  Industry,  John Wiley  and  Sons,
Inc., New York, pp 379-385 (1954).

ASTM Manual for Conducting an Interlabora-
tory  Study  of a Test  Method, ASTM STP
No. 335,  Am.  Soc.  Testing & Mats. (1963).

Mandel, John  and  Lashof,  T.W., "The  Inter-
laboratory  Evaluation  of  Testing Methods,"
ASTM Bulletin, No. 239, p 53  (TP133) (July
1959).

Recommended Practice for  Dealing with Out-
lying  Observations,  ASTM   Designation:
E178-68, Book of ASTM Standards, Part 30
(1968).

ASTM STP No. 335,  op. cit., p 27.

Ibid, p 34.

Ibid, p 28.
                                               B-5

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