GUIDELINE SERIES
OAQPS NO. 1.2-007
AIR QUALITY MONITORING INTERIM
GUIDANCE
US. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
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45OR73115
AIR QUALITY MONITORING
INTERIM GUIDANCE
August 1973
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TABLE OF CONTENTS
Page
PREFACE i
1. INTRODUCTION 1
2. MANDATES FOR AIR QUALITY MONITORING 5
3. AIR QUALITY DATA ACQUISITION 10
3.1 General Network Design Considerations 10
3.2 Size of Monitoring Network 12
3.3 Location of Monitoring Stations 15
3.4 Sampling Site Characteristics •••• 16
3.4.1 General Siting Considerations 16
3.4.2 Specific Siting Considerations 18
3.5 Sampling Frequency 18
3.6 Instrumentation 23
3.7 Laboratory Quality Assurance 28
4. AIR QUALITY DATA ANALYSIS 30
5. AIR QUALITY MONITORING EVALUATION 34
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LIST OF TABLES AND FIGURES
Page
Table 1. RECOMMENDED MINIMUM NUMBER OF AIR QUALITY
MONITORING SITES 14
Table 2. SITING GUIDELINES FOR AREAS OF ESTIMATED
MAXIMUM POLLUTANT CONCENTRATIONS 19
Table 3. MAJOR STATIONARY POLLUTANT SOURCES 21
Table 4. CLASSIFICATION OF AIR POLLUTION SAMPLING
TECHNIQUES 24
Figure 1. AIR QUALITY DATA FLOW 33
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PREFACE
The Monitoring an>l Data Analysis Division of the
Office of Air Quality Planning and Standards has prepared
this report entitled "Air Quality Monitoring Interim
Guidance" for use by the Regional Offices of the Environ-
mental Protection Agency. The purpose of the report is
to provide general guidance information on current air
quality monitoring requirements and principles. This will
allow the Regional Offices to prioritize their FY1974 moni-
toring related resources and program activities. Adherence
to the guidance presented in the report will, hopefully,
ensure mutually compatible ambient air quality data acqui-
sition by all States and Regions and will also better allow
the Regional Offices to evaluate State monitoring programs
and related activities. Moreover, risks involved in policy
decisions concerning National Ambient Air Quality Standards
should be minimized. This report is intended to update
previously issued official and informal air quality monitoring
documents and will serve on an interim basis until more specific
and detailed guidance documents are developed.
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1. INTRODUCTION
The purposi of this report, a first in a series to be
issued by the Monitoring and Data Analysis Division of the
Office of Air Quality Planning and Standards, is to provide
the Regional Offices of EPA with a general overview of both
the issues and principles involved with the establishment and
operation of the air quality monitoring program which is
required under the St< te Implementation Planning pro< ess.
It is expected that tltrough a thorough understanding of these
considerations that the Regional Offices will be better•able
to prioritize their FY1974 monitoring related program activities
and resource allocations.
Information presented in this report* is intended to
fulfill the following immediate objectives:
Ensure that mutually compatible ambient
air quality data are obtained by all
States and Regions.
Minimize risks associated with policy
decisions involving National Ambient
Air Quality Standards.
•Guidance presented in this report is geared toward the six
criteria pollutants (sulfur dioxide, particulates, carbon
monoxide, photochemical oxidants, hydrocarbons, nitrogen
dioxide) and present State Implementation Plan requirements.
Future issuances will be concerned with proposed SIP require-
ments dealing with such issues as complex sources and non-
degradation.
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Better allow the Regional Offices to
evaluate State and local air monitoring
programs and related activities.
Summarize and update existing monitoring
information in one document based on the
present state of knowledge.
Previous issuances by EPA related to air quality monitoring
have been based more on operational experience with monitoring
networks than on developmental research studies. This report
is no exception. Information and guidance gleaned from such
experience are an indirect outgrowth of monitoring activities
which were intended to provide a basic characterization of the
ambient air quality in the general atmosphere of an urban or
rural area or around a specific source. Therefore, present
guidance is of necessity limited by the constraints within which
these previous efforts were conducted. Future guidance will
also be based to some degree on retrospective analyses of existing
networks and on data available from various on-going research
projects. This should be the case until the monitoring infor-
mation which is being obtained from evolving State and local
networks can be evaluated in terms of how well it fulfills the
decision-making needs of the Regional Offices. These needs
relate to:
EPA's desire to minimize risks in making
yes/no decisions relative to the progress
States are making toward attainment or non-
attainment of ambient air quality standards;
surveillance and subsequent action with
respect to episodes; attainment and main-
tenance of standards.
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EPA's ability to ensure the representativeness
of State derived data.
EPA's ability to make risk decisions with re-
spect to prioritization, strategy development
and i.esource allocation.
Interim guidance presented in this report should allow the
Regional Offices to develop the bases for the various decisions
related to the above with some degree of confidence. It should
also allow them to better discharge their monitoring responsi-
bilities which specifically include the ability to:
Ensure that the States
Utilize standard sampling metho-
dologies and proper quality control
procedures
Operate and maintain adequate
analytical laboratories
Enter air quality data into the
National Aerbmetric Data Bank.
, Check the validity of incoming data
Obtain episode data
Evaluate State and local air monitoring networks
Establish quality assurance programs
. Assist in identifying "hot spots"
Analyze data to assess compliance with
National Ambient Air Quality Standards
Predict trends in air quality
Develop and operate regional monitoring programs
which meet national and regional monitoring ob-
jectives.
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Information presented in this report will serve on an
interim basis until more explicit and detailed guidance is
developed by the Monitoring and Data Analysis Division.
The follow ng sections include a brief re iew of EPA
mandated monitoring activities, factors involved in the
physical collection of air quality data, general air quality
data handling procedures and an example of an air quality
monitoring evaluation process.
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2. MANDATES FOR AIR QUALITY MONITORING
Air quality surveillance is the systematic collection and
evaluation of aerometric and related data which include pollutant
concentrations, source operating characteristics and emissions,
and certain meteorological parameters. This report is
concerned with monitoring operations* which are designed to
measure pollutants emitted to or present in the atmosphere.
Information provided from these monitoring operations should
be responsive to the following objectives:
.1. Judging compliance with and/or progress
made toward meeting ambient air quality
standards.
2. Activating emergency control procedures
intended to prevent air pollution episodes.
3. Determining pollution trends throughout
a region including the nonurban areas.
4. Developing a data base for the assessment
of pollutant effects; land use and trans-
portation planning; study of pollutant
interactions, patterns and trends;
evaluation of abatement strategies and
direct enforcement of control regulations;
and to improve the reliability of
diffusion models through validation
procedures.
The requirements and need for monitoring are closely
related to the pollution control requirements specified by the
* These operations include three distinct but interrelated
elements: sampling networks, laboratory support, and data
acquisition and analysis.
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Clean Air Act of 1967 and the Clean Air Amendments of 1970.
This legislation authorizes EPA to:
Promulgate national ambient air quality
standards
Promulgate national emission standards
of performance for new stationary
standards
Promulgate national emission standards
for hazardous pollutants
Promulgate national emission standards
for motor vehicles and aircraft .
The development of these standards and subsequent enforcement
require '•hat information on ambient concentrations of pollutants
concerned by this legislation be available.
Specifically/ the following monitoring related activities
are mandated*:
1. Clean Air Act, December 1970, Section 110(a)
(2) (C)
Each State shall adopt a plan which provides
for the implementation, maintenance and
enforcement of primary and secondary standards
and which includes..."provision for
establishment and operation of appropriate
devices, methods, systems, and procedures
necessary to (i) monitor, compile, and
analyze data on ambient air quality and
(ii) upon request, make such data available
to the Administrator."
*As of the date of this report, some of the Federal Register
Notices are for proposed regulations. Therefore, the monitoring
activities alluded to in these proposed regulations are not
nov: required (e.g., for complex sources and no significant
deterioration).
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2. Federal Register, April 30, 1971,
Volume 36 Number 84
a. Details national primary and secondary
ambient air quality standards for
sulfur dioxide, particulates, carbon
monoxide, photochemical oxidants, hydro-
carbons, and nitrogen dioxide.
b. Specifies standard reference methods
for above pollutants.*
3. Federal Register, August 14, 1971,
Volume 36 Number 158
a. Classification of Regions according
to pollutant concentrations.
b. Quarterly air quality reports are
required.
c. Minimum air quality network require-
ments are delineated.
d. At least one sampling site must be
located in the area of estimated
maximum pollutant concentration.
e. Description of the air quality
surveillance system should include:
Basis for the design of the system
Location of samplers by UTM grid
coordinates
Sampling schedules
Methods of sampling and analyses
Method of data handling and analysis
procedures
. Timetable for installation of
additional equipment
. Stations selected for monitoring
during episodes
*See 7b
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4. Federal Register, February 1, 1973,
Volume 38 Number 21
Quarterly reports submitted by the States
to the Administrator through appropriate
Regional Office shall include all air
quality data from the surveillance
n twork:
according to the SAROAD format
. within 15 days after the end of
each reporting period.
5. Federal Register, April 18, 1973,
Volume 38 Number 74 (proposed rules)
Determinations of impact of mobile
source emissions as a result of a
"complex" source require data on:
. present air quality, topography,
meteorology
size of facility, nature, design
expected mode of operation.
6. Federal Register, May 7, 1973,
Volume 38 Number 87 (proposed rules)
Revises secondary standards for sulfur
dioxide by revoking the annual standard.
7. Federal Register, June 8, 1973,
Volume 38 Number 110 (proposed rules)
a. In transportation control measures
development, (hydrocarbon, nitrogen
dioxide) carbon monoxide and photo-
chemical oxidant data must be
compatible with the emissions
inventory for the subregion involved.
b. Specifies three tentative candidate
reference methods for the determination
of nitrogen dioxide. (Replaces
method promulgated on April 30, 1971)
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8. Federal Register, June IB, 1973,
Volume 38 Number 116 (proposed rules)
Areas which due to growth rate will
exceed National Ambient Air Quality
Standards in the next 10 years should
be identified and data on air quality
and human activity should be provided.
9. Federal Register, July 16, 1973,
Volume 38 Number 135 (proposed rules)
For purposes of evaluating the pre-
vention of significant air quality
deterioration, the following are required;
1972 baseline particulate and
sulfur dioxide data including the
maximum concentrations in an area.
. Where a source (as described in the
Federal Register) is to be con-
structed a minimum of 2 continuous
instruments for sulfur dioxide and/or
2 intermittent instruments for
particulate matter.
The source monitor instruments
should be located in the zone of
expected maximum concentration as
determined by diffusion modeling.
The source should summarize the data
monthly and report to the State
semiannually.
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3. AIR QUALITY DATA ACQUISITION
The levels and distributions of air quality are
often quite ^ariabL in both time und space. Knowledge of
these variations, their significance and their causes, is
essential for the proper interpretation of air quality data.
The degree to which these variations are detected and
quantified depends, in large part, on the adequacy of
coverage and "representativeness"* of monitoring sites within
an Air Quality Control Region (AQCR). Available pollutant
.measurements for many AQCR's are inadequate for comprehensive
air quality and trend analyses. However, it is expected that
through adherence to, and consideration of, the general
factors and principles discussed below that the quantity,
quality and uniformity of data being collected will be en-
hanced and that the data requirements of EPA's monitoring
objectives will be fulfilled.
3.1 General Network Design Considerations
The development of network designs should be based on
knowledge of the existing pollution levels and patterns within
the AQCR. The areas of highest pollution levels must be
*Representativeness connotes the effect of sampler placement
on the usability of the measurements.
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defined, together with geographical and temporal variations
in the ambient levels. Isopleth maps of ambient concentrations
derived from past sampling efforts and/or from diffusion
modeling are the best tools for determining the number of
stations needed and for suggesting station locations. Also,
information on meteorological parameters, topography, population
distribution, present and projected land uses including areas
where growth is anticipated, pollution sources and areas of
potential sources is extremely useful in network design. Where
isopleth maps are not available, information from various
organizations such as the Bureau of Census and local planning
agencies can provide the basis for initial designs. Additionally,
information on emission densities and/or land use can be used
together with wind-rose data to pinpoint areas of expected
higher concentrations. Maps of population density are essential
in locating stations for monitoring during episodes and provide
a general indication of human exposure in relation to various
source distribution patterns.
For many areas, information as described above may be
wholly inadequate and/or unavailable. In these cases, the re-
sulting networks will need to be modified as more information
and experience are obtained. But this should be true even in
those areas where adequate information is available. Network
design should be continually assessed and evaluated in terms
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of how well the resulting data fulfills the previously dis-
cussed monitoring objectives keeping in mind the need for moni-
toring the data base required for long term trend analysis. As
more resources become available (and based on the objectives-
evaluation proc ss), network designs should be upgraded accord-
ingly.
3.2 Size of Monitoring Network
The number of sampling stations required depends primarily
on the existing pollution levels, their variability, and the
size of the region.* The size of the network must be adequate
to allow for definition of the area(s) where ambient concen-
trations may be expected to exceed air quality standards.
Information on air quality in other areas, including the non-
urban portions of the region, should also be collected. Also,
issues such as complex sources, transportation control measures,
hot spots, supplementary control systems, and fugitive dust
problems may influence the monitoring network size.
A first approximation of the number of stations required
in a region may be obtained from general curves based on a
qualitative evaluation of cities of different population classes
in terms of their existing networks, pollution patterns, geo-
graphic distribution of sources, and the like.** The relationship
* Most obviously availability of resources is also an important
consideration.
** Guidelines: Air Quality—Survei1 Vance Networks, Office of
Air Programs Publication No. AP-98, U.S. EPA, May 1971.
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between population and network size (see below) was derived from
such investigations, combined with experience. In general, popu-
lation is a good index to network size. In certain situations,
however, such as the relative absence of sulfur dioxide in western
portions of the t lited States, such relationships are not appli-
cable. In these situations, additional information, such as source
strengths and their locations, is essential before network size
can be determined.
Based on the above population relationship and according to a
priority classification assigned to each AQCR for carbon monoxide,
nitrogen dioxide, parti iulate matter, photochemical oxidants, and
sulfur dioxide, the minimum size of an air quality monitoring net-
work can be determined. An AQCR is assigned a priority classifica-
tion according to a comparison of its air quality levels to the air
quality standards. Generally in priority I AQCR's the air quality is
poorer than primary standards. In priority II regions it is between
secondary and primary levels and in priority III regions it is better
than secondary standards. For particulate matter and sulfur dioxide,
the classification criteria provide for priorities of I,II,or III
while for carbon monoxide, nitrogen dioxide, and photochemical oxi-
dants priorities of I or III are applicable.
Table I presents the recommended minimum number* of air quality
monitoring sites by AQCR classification and population class. (Note
This number omits sites for monitoring complex sources, non-
degrauaticn, transportation control measures, supplementary
control systems, fugitive dust. Guidance on these issues is
forthcoming.
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Table 1. RECOMMENDED MINIMUM NUMBER OF AIR QUALITY MONITORING SITES
C'ln*Kthn»lloii I'ollilliuil Mi'ivlMrmiMil Mirlliinl ' Minimum fri'iiui'ili'} of MllnlilloK llr^l"!! po|nlli|lion \tliiiiiiilni iiiintl..-i .if *1,
of tr|;l'm i|llalll\ niimiliii Ml)* i;.**
I Suvpl'IMli'd (ill 111 Hi ill . Midi volume ^uiipl C lln|._'l-llolll .-anipl.-i.ni) li.la.V V l,i"« i ill |l»l.'«"l I
lim.O' i.ndo.Kin i • ni; |i,
Above S.i»«M»»i . ...
Tape sampler. Olipsample every J hours One pel JMl.tmn pnpnl.iiii.n • -i;(
tltPluIlt files.
Sulfur dlntldp rararosanilln- or eigiiivalent * One 'Jl-lioilr sample I'Very tidais LI-fi tlian H»>.'»»' . 3
(Hits LiUlililiT).* IIKI.IIIKP l.l»»l.i«»l .'.5-l-n.Sper Inn.gnn l-.p'l! .': . •
l.uuo.oiil s.ini.imo . . liJ-o.lS |»T li»i.>»«>p"pi r,:i5 piiase clieiiiiluniine--eiire Cuiitinuoti* . . ... Less than HHI.OIBI 1.
oreitulvalent.1 lt»),IWO••S.WII.imi 1 + 0.1.1 p,M l(«).i2l-!iniirniimplprvpry dilny* • S.
Ta|M* ^aili|iler . One sample every 'i lioui.^. . . '. I.
Sulfur ilioiid.- I' .i.niNumM - 01 ei|lllval.'iil •*. One -'Mii'in r-atnple ever*' lida>-' 3.
("nntlnuiiii-.. ...
IH* . Susri»'ii.l^l p:oiii-iil lie- IfiL'h volii :i.- »-i i|i| T 1 »ne'JI tioursampli»e\vr> ildavJ •
Slllfui• dioxide P.I' I .(Uival." I ". lllie'.l 1:..iir-illlpl"PV..|yrn1.y<
• ErilliViilriit Infil r•iiiiliMirs:ini|i|.^ I..T \i-tr.
>• Kqillv:llrl!l In -i. r ii.'l'>lii - in'pli'- |» r > .-.n .
• Tul:il |uipiil:iiiiiii..(.1 iriMiin. W h MI r.-i|'iii!.-l niu.iiixr tl^i'.l ll.riitluln-llt Itli' illStl lllniMII ~v Sf.-Mi In Irir! *< t •*'•>•!
to Ihr :\\t strr.i-iO. i .'• h . :;:.• |'|I..N>:;J.-I: if I i.-i.-vi inn . |ii..-. .ud H.> .ir.- r.-rn'.v. .(i, uit-l 11> i tn< ^uriirniil.''! I'.u ii..>.inilin.1 rrocr'lurv.
• K'|Ulv;il.'iit liii-ti:'"H< i;.i- ' l.n"n il".-: il'l.'.r S.-|i ir-iiinli—-I 'ill I'.ylii- I'imv. i>lu:i — Klalllp liillU'.illnil I li'l.•client.
' K'|lllv:il'-!.t ru.-ll:--I- ;ii' I I'm i. ii;." Imliil" <'- .'.."i i ,:!i-l rlr I )rli't.T inn I pr-v !.|."| :i rurK'i't inn if HI uii- (or .SO.. :uiil N'l>;>. C.'l VV I'lioloini-ll k- 1),-!. i-li'.n it'. •<• mr
(|irovl'l..l riiiMiK'iis -ili"-i i- ]:; i'l.- ("i J.I. rl' > n,.- -ill.-' nil- -.- . .unl .:>' Cli'-r.:l!illnih--. nv,- M. Hi.His i|ill,.| iiiu fiu:n limt of III.- u-d-i .'in-.- nii'tlnvl.
• II Is :i"iim.-l ii..,: il.- K -,l -..,; i..: v.-hii-l '.I-M-.,, Miir!:ii-l- tvill ;i,-|,i. -\v .ml ni:iliiC:iin Hi,- n:illiin:il "l.inil.il.l- for r:irliiiii niiino\Uli-. nllii^i-n Uum-T-. .ri I
phninclii'inic:!! o\M.ini v Ii <-iffi>ii-. ii'i nininii'i i:.i; .
fc In lnii'i->l;ifii ri'i.-i"'i'. lit-- iiiriil..-! nf-'ii.-- i.'niiii-i| .^li..iilil In* |iroriit>'f:n-li >: MI- on u |in|>iit:illoii 1i-ili>-.| :•• ''1-1
FKPKRAI. IO.CISTKK on API :i». !'•"! <•<•> I K «!•>•. uih.i m,.||i.i-l? iihii-tlu-r wiili Ilios,. s|«-tiln.f tniilrr foolnolrs i«li. ii-i. anil i.f; will b>- consiilrivil i'i|iiiv;ilrni .- : y
Illivl III.-(.jlliiwiiiK |KMf'i:;ii:itwi|»''-ili(-'iU>ir..
Sulfur illoxldi- C'nrlioit ntonotliji' IMiotoclirinirnl uxiil:mt
(corrn'liMl for NO; an.I ?u,
Itaiiri' il J.iiJO »?. m." 10 1 p.p.in.1 0-38 nip.'in.1 (ft-Jii p.p.m.) 0->M)0ir.'in."0 il.s p.p.m.V
Mliiiinilin ilrli'i-l il.l.- si-iisilivily '.11 vj. in ' ni.nl p.p.m.) n.A IHK..III.' i".5 p p.ni.l -•<) ul.'m." .ii.ul p.|i.ln.'l.
KI-'Mi , iNip,.i>-, i,i s ni;im'.." 5 miiiul.-s , S mlnuti-i.
Kail tiiiu'. !"0 PIMI-. :ir A niiinit.-? ... , .. . 5 ntintili'S A niiniili^.
ZITO drift *1 p»-i-i'»Mit prr day uiid •«' p-ro»'hl pi-r *t pi'toi-ni ju-r itiy anil *'„' p'TO'iil p»ir *l ih-n-i'iil p,*r il.iy an.l * J p,-n-» -.:
^ s. 3 days. 3 day*.
1'ivciMioii *•„> |M-rrrii( *4 pvrei-nl *>4 pnrwiif.
f)p<-r.itinn p.-riu,l 3 dnys 3 days 3 day.'.
NuUp *l).J p.TO nt i full wall-) *O.S |H>rvpul (full si-aW *».5 |N>rr"iit ifull scilr).
Jnti-rfi-rrni'i' r-|iiiv.i!i-nl Ltl **(-'- ni.- vO.OI p.p.in.) I.I niu.'m.1 (1 p.p.m.) 21* MR.'ill.1 1<*.*>1 p.p.m.).
On.-ralinp Irmp.'Mtur. iltict nation *S'«' *»' (! *J° c*.
Limarity .'p.-n-.-ni Uull seal.-) :'|)i-rci'nt l.fnll si-.ilc) 2 pi-reviU I'ftill scalr).
Thp various ^p'-i'iru-.ltion^ uri» il>Tini*d as fol1uw<:
H.IIIKP: Till- !.:iiii!'ium ami iiiaxiiinnn nn-:i-nr.-:ii,-iil limits. v
Miniinllin ili'ft-cl.ilil'' >'i'i.*itivity: Th.> ^inall«-»l :i::-.niliil of input coiiri'iitr.itfoii which can Iw d»'l*cti-il a-i concentration lppi-ii3ch»';i toro.
lr tilin* '.41 p'-rt-.-nl: 'rhi* in'. I v;ii i>.-tv\,^'ti iin: :.i! r.^iionsi1 tiiiu* anil time t>i :HI pi*rc*.|il rvs|> |---r.-,-nt : Th-' ini.-rv il h.-twr.-n iniii.i! r,-sp,)iiM< iinn> atut t.in:r to '*) pri-ri'iit n*<|ioM..i>- :tfi,*r a iitop ili-rr>.ainrr In iii-iiirni-nt uiitpiit ov,-r a siat.-il tliiu- p.-riml "f tiniiljii^tnl cnnliiiiinus up. -ration, whrn tin- Input I'nncvntrailun is ?,TO.
Span ill lit. 'I1:.-- t'.i.in-.'i. in in^li u:i;.-:,t output uvvr i -i.il.-i] p.-n.i.| of un^.ljii.i. .| continuiiu> opi.r.ili.in. wlii-n tin- injMlt i-.iiu'''ntr.iliiMi s a slat.-il upsPal.- v il-i-^.
IMvi'iMoit: T ..... li-ji,-,- ttl :i-jr,-,-in,-nt ii.-t\vi-,-n r,-p.-.ii. ,1 iih'a.-ui'<-iii'>nt.s oi tlii- .-.cm' caiti-i'iitiation iwtilrh shall In1 tiu- iiti'lpuint ol tin1 -l,iti'd rant;.-) oxpri-.---,-!
•vt-rasi- di'vhiij.in "f I!-,- -:i1.-!i. n-vii!ts from th,- m.-.u,.
dpi •'. iin "i p ::•»!: I ;-.. p. iio.| of tiiin- ov.-r w;i::!i tin- i:i-lruni"nt cm lio npi>cti"t to opiTaliMin UliMnli-'l within spi-cilicalinn*.
Sols,-: SIMI-.I in. OIL- •!• n. it ions from a in. an i. ill put not ran -.-'I iiy input iiinivhtralliiii Chanel's.
IniiTf..r..|..c.. i-iuiv .il-iit: 1 ho portion of iinlirai,-! i-oi.i-.-ntratiiin due to Hi.- Inlal of tin. inl.-ii'iTi.nr.v- commonly fouml h> muMi-iit air.
Oiv-ralini; i>'iup>.t itiin- ilinMiKiiiiii: Tlu> anilii. in li':np,T.ituri- Iliu tuati ..... irrr which stal.-'l sp,-nlir:iticiii< will !»• m.-l.
MucariLy: The inaiinium dcvi.itiuti b. twi-i-n an .11 ui.il iii?lruiiioiil r.-.nlinp and tin: ri-uJinj: prinlK-li-.l l>y a straight Iin" itra»'n Ix-twci'ti upper Slid lower ratU'i
pointj.
EPA is currently evaluating three measurement techniques for
NO, and will publish a new reference method by March"l974. The
method chosen will prescribe the sampling frequency and minimum
number of air monitoring sites.
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that the standard reference method for nitrogen dioxide is cur-
rently being roovaluatcd in terms of three proposed tentative
candidate methods. Meanwhile, in cases in which it appears de-
sirable that State N02 monitoring activities be continued, such
continuation is to be encouraged provided that either chemilumin-
escence or Saltzman methods are used.)
3.3 Location of Monitoring Stations
The location of sampling stations must be such that the
resulting information can be used to fulfill the data require-
ments of the previously presented monitoring objectives. The
monitoring network should consist of stations that are:
a. Pollution oriented
Areas most heavily polluted must be
identified and monitored* It is in
these areas that progress toward
meeting air quality standards is
most critical.
b. Population oriented
A portion of the network must be
located according to population
distribution. This is especially
important during episodes.
c. Representative of the Region
Area-wide data are needed to show
conformity or lack of to the air
quality standards. This includes both
urban and rural portions of the AQCR.
In rural areas, consideration must be
given to places where growth is
anticipated or new sources are ex-
pected to locate.
d. Source category and/or source oriented
These stations provide a. measure of the
effectiveness of control strategies.
e. Background oriented
For assessing the quality of air entering the
Region, stations must be situated on the peri-
phery of the Region.
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Many stations are capable of meeting more than one of the
above general criteria. On a priority basis, the stations
should be capable of at least providing information on:
Areas of estimated maximum concentration
in all major urban complexes of the Region
(particulates and sulfur dioxidt in priority
I and IA Regions).
Transportation related pollutants in those
cities and regions requiring transportation
control measures.
. Trends and prorgress toward achievement of
National Ambient Air Quality Standards
. Pollutant levels during episodes
3.4 Sampling Site Characteristics
In the selection of a particular site for a single sampler
or a complex station, it is essential that the sampler(s)
be situated to yield data representative of the location and
not be unduly influenced by the immediate surroundings. Although
no definitive information is available concerning how air quality
measurements are affected by the nearness of buildings, height
from ground, and the like, both general and specific guidance
can be provided based on operational experience.
3.4.1 General Siting Considerations
a. Avoid sites where there are res-
trictions to air flow in the
vicinity of the air inlet —
such as adjacent to buildings, para-
pets, trees.
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17
b. Avoid sampling sites that are unduly
influenced by downwash from a minor
local source or by reentrainment of
ground dust, such as a stack located
on the roof of a building where the
air inlet is located or close to
ground level near an unpaved road.
In the latter case, either elevate
the sampler intake above the level of
maximum ground turbulence effect or
place the sampler intake away from
the source of ground dust.
c. The monitoring site should be generally
inaccessible to the public; have adequate
security, electricity and plumbing.
d. Uniformity in height above ground
level is desirable. Roof top*
samplers should be utilized in moderate
to high density areas (in terms of
structures). Ground level samplers
should be utilized in low or sparse
density areas (in terms of structures).
•Roof top is defined as the average building height above
ground for a particular section of the Region.
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18
3.4.2 Specific Siting Considerations
Specific guidelines for siting air monitoring
stations in areas of maximum pollutant concen-
trations are presented in Table 2. In addition,
Table 3 presents specific stationary pollutant
sources for which monitoring (e.g., for hot
spots) should be undertaken, where applicable.
3.5 Sampling Frequency
Sampling averaging times depend upon the primary use of
the data. To show compliance with, or progress towards meeting
ambient air quality standards, the sampling equipment must be
capable of producing data consistent with the averaging times
specified by the standards. For example, if the standards are
set in terms of daily and hourly averages, then the sampling
frequencies must be in the same averaging time.
Although standards for particulates and sulfur dioxide,
for example, are in terms of annual averages and maximum daily
concentrations,it is not economically feasible to operate the entire
network on a daily basis. Adequate coverage may be maintained with
intermittent sampling at frequencies calculated statistically for
desired levels of precision. In order to increase the statistical
precision of the estimate for the annual average, a systematic
sampling schedule should be utilized.* Also, the frequency of
air monitoring necessary to characterize an a^r pollutant for a
given time period and area can be determined from equations that
* G. Akland, Design of Sampling Schedules, JAPCA22(4), April 1972.
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Table 2. SITING GUIDELINES FOR AREAS OF ESTIMATED MAXIMUM POLLUTANT CONCENTRATIONS
POSITION OF AIR INLET
POLLUTANT CATEGORY POLLUTANT
Primary Stationary
Source Pollutant
Primary Mobile
Source Pollutant
SO.
NO,
Particulates
CO (1-hour
averaging time)
CO (8-hour
averaging time)
STATION LOCATION
SUPPORTING
STRUCTURE
Determined from atmosphere Ground or
diffusion model, historical Roof Top
data, emission density, and
representative of population
exposure.
Same as above
Same as above
Representing area of high
traffic density, slow
moving traffic & obstruc-
tions to air flow (tall
buildings) & pedestrian
population such as major
downtown traffic inter-
sections. 10-15 feet
from street curb.
Representing area of high
traffic density in resi-
dential area such as major
thoroughfare in center city
or suburban area. 10-15
feet from street curb.
Ground or
Roof Top
Roof Top
Ground
Ground
VERTICAL CLEARANCE
ABOVE SUPPORTING
STRUCTURE. F.EET
10-15
10-15
HORIZONTAL CLEARANC
BEYOND SUPPORTING
STRUCTURE, FEETa
> 5
>5
10-15
10-15
10-15
5-6
> 5
•> 5
•K
5-6
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Table 2. SITING GUIDELIKES FOR AREAS OF ESTIHATED MAXIMUM POLLUTANT CONCENTRATIONS (CONTINUED)
POLLUTANT CATEGORY POLLUTANT
Secondary Pollutant Oxidants
NO,
STATION LOCATION
Representing residential
area downwind of downtown
area (5-15 miles from down-
town and > 300 feet from
major traffic arteries or
parking areas).
Same as above
POSITION OF AIR INLET
SUPPORTING
STRUCTURE
Ground or
Roof Top
VERTICAL CLEARANCE
ABOVE SUPPORTING
STRUCTURE. F.EET
10-15
10-15
Ground or
Roof Top
HORIZONTAL CLEARANCE
BEYOND SUPPORTING
STRUCTURE. FEETa
* 5
>5
10-15
10-15
>5
>5
K
C
a Not applicable where air inlet is located above supporting structure.
b Downwind of prevailing daytime wind direction during oxidant season.
c When standard reference method (or equivalent) is suggested.
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Table 3. MAJOR STATIONARY POLLUTANT SOURCES
POLLUTANT
SOURCE* Particulates CO SO^ HC NOl
Asphalt concrete plants X
Petroleum refineries X X X x
Storage vessels for
petroleum liquids X
Secondary lead smelter X
Secondary brass & bronze
production plants X -
Iron and steel plants X x
Sewage treatment plants X
Fossil fuel steam electric X X 3
(> 1000 million BTU per
household input)
Cool cleaning plants X
Primary aluminum ore reduction X
Lime plants X
Phosphate rock crushing X
By product coke oven batteries X
Municipal incinerators X
(> 250 tons per day of
refuse)
Portland cement plants X
Nitric acid plants
Sulfuric acid plants X
*Also, any source emitting greater than 4000 tons per year
of these pollutants.
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Table 3. MAJOR STATIONARY POLLUTANT SOURCES (CONTINUED)
POLLUTANT
SOURCE*
Carbon black plants
Feed & grain mills
Sulfur recovery plants
Copper, zinc, lead smelters
Pulp and papermills
Grey iron cupolas
X
X
X
X
X
X
X
X
Particulates CO S02 HC NO
X XX
X
*Also, any source emitting greater than 4000 tons per year
of these pollutants.
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predict the precision of the sample mean of the air pollutant
as a function of: the frequency of sampling, the standard devia-
tion of the logs of the air pollutant measurements, and the level
of confidence*. Table 1 presents the recommended sampling fre-
quencies based on the above considerations. It should be noted
that for detection of maximum pollutant concentrations the samp-
ling frequencies may require modification in certain portions of
the AQCR.
3.6 Instrumentation
A variety of sampling devices and instruments are being
used to collect samples and measure ambient air quality.
Mechanical samplers are most generally used to collect integrated
samples in the field. (Integrated sampling is conducted over a
given time period to yield a single sample to represent the
entire time period.) In automatic sampler-analyzers, the
collection and analytical processes are combined in a single
device. This type of instrument produces a continuous analysis,
with the output in a machine-readable format or in a form suitable
for telemetry to a central data-acquisition facility. Table 4
summarizes general information on types of instrumentation, use,
specificity and associated costs.
Standard reference methods for the operation of particulate,
sulfur dioxide, carbon monoxide, photochemical oxidant and
hydrocarbon instrumentation are specified in the Federal Register
*W.F. Hunt/ The Precision Associated with the Sampling
Frequency of Log-Normally Distributed Air Pollutant
Measurements, JAPCA 22(9), September 1972.
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Table 4, CLASSIFICATION OF AIR POLLUTION SAMPLING TECHNIQUES
Type
Mechanical
Hi-Vol
Gas
• ampler
Spot tape
• ampler
Automatic
Gas
Harticulate
• orting
(automatic
tape)
Use
InlcK rated
quantification
Integrated
quantification
of gas
Relative
soiling index
Continuous
analysis of
gaseous
pollutants
Continuous
analysis of
soiling rate
Specificity
Total suspended
particulal . and
multiple specific
pollutants
SOi. NO,;
Unknown
Single gas or
group of
related gases
Unknown
Common
averaging
time
24 hours
24 hours
i hours
Continuous
sample
integration
usually 1*
IS months
(Same At
above)
Relative
C0it»
Moderate
Moderate
Low
Moderate
to high
Moderate
Required
training of
personnel"
Moderate
High
Low
Moderate
to high
Moderate
Remarks
Detailed chemical analysis of
Hi-Vol and gas samples require
sophisticated laboratory train-
ed chemists, and is costly.
Provides only a rough, rela-
tive index of particulate soiling.
Continuous measurements
allow use of any desired aver-
aging lime by computation.
Accuracy is generally much
belter than other methods.
Calibration is simplified. Data
is available instantaneously.
l.uw refers to $0-Sf>00; Moderate refers to $*00-$2000: and High refers to above $2000.
Low requires common maintenance; Moderate requires a technician; and High requires an experienced technician or
professional with professional support staff.
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of April 30, 1971. In addition, three tentative candidate
reference methods for nitrogen dioxide have been proposed in
the June 8, 1973, Federal Register.
Other sampling and analysis methods are acceptable and
will be considered equivalent to the reference methods if
it can be demonstrated to the EPA Administrator's satisfaction
that they have a consistent relationship to the reference
method and/or at the Administrator's discretion meet various
performance specifications. Such specifications include the
following factors:
Sensitivity
Stability and reliability
Zero drift
Reproducibility
Precision
Response time
Calibration
Accuracy
The actual selection of particular monitoring equipment
should follow a careful evaluation of information pertaining
to the instrumental specifications and a knowledge of the user's
specific application. This selection process should be
objective and include considerations of (e.g., for automatic
air monitoring equipment*):
*Field Operations Guide for Automatic Air Monitoring Equipment,
U.S. EPA, October 1972.
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26
a. Instrument description factors
Application
Measurement principle
. Schematic diagram
Auxiliary equipment
b. Installation and operation factors
Space requirements
. Weight
. Power requirements
Temperature operating range
Humidity operating range
Vibration operating range
Portability
Signal output
Air sampling rate
Sample line pressure
Calibration
Sample line construction
Reagent flow rate
Reagent consumption
c. Performance factors
Range
Sensitivity
Rise time
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27
Fall time
Zero drift
Span drift
Precision
. Operation period
Noise
Interference
., Operating temperature fluctuation
Linearity
Specificity
The objective evaluation process for equipment selection
should also be based on a general understanding of the measure-
ment technique employed by various monitors. Operational
principles commonly incorporated in continuous air monitoring
instrumentation include:
Conductivity
Colorimetry
Coulometry
Flame photometry
Flame ionization
Nondispersive infrared photometry
Reflectance and transmittance
. Nephelometry
. Chemiluminescence
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28
Information on these principles including their specifici-
ties and interferences is presented in the previously referred
Field Operations Guide.
\
The selection of a specific monitoring instrument should
be made only after a comprehensive evaluation which considers the
above factors and principles. It is strongly recommended that no
instrument be purchased unless the manufacturer provides a guaran-
tee that the instrument will perform in accordance with the speci-
fications published in either the 30 April 1971 Federal Register
or the draft equivalency guideline document entitled "Ambient Air
Monitoring Equivalent and Reference Methods." Interim guidance
on the selection of air quality monitoring instrumentation can be
obtained from the Quality Assurance and Environmental Monitoring
Laboratory at NERC, RTP/N.C. QAEML will provide this guidance until
equivalency guidelines on methods and instrumentation are published
in the Federal Register.
3.7 Laboratory Quality Assurance
Quality assurance is an integral part of any viable
monitoring effort. It begins when the selected methodology
obtains a valid measure of the analytical parameter, when
the laboratory tools (reagents, instruments, standards) are
of invariant quality, and when the operational techniques
used ensure exacting replication for the entire analytical
procedure. The objective of quality assurance is to produce
reliable data for decision making.
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The two primary aspect?; of a quality assurance program
arc standardization and quality control. While standardization
development (production of reference methods, equivalency
guidelines, monitoring procedures and guidelines) is the general
responsibility of EPA, the National Bureau of Standards,
and certain professional associations and committees, quality
control is within the purview of State air pollution control
laboratories.
The Regional Offices should assist the States in
developing an effective quality control program through the
implementation of the following:
Training of managers and operators
Data reporting schemes which include
evidence of quality control considerations
Operation of an intralaboratory
quality control program
Periodic, random checking of
instrumentation and equipment
calibration
Cross-checking of samples
Checking of reagents, reference
samples, and quality of personnel
Participation in an interlaboratory
testing program
Use of formalized schedules, procedures,
logbooks and calibration curves for all
monitors.
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30
4. AIR QUALITY DATA ANALYSIS
Even the best air quality data are of little value
unless they are properly analyzed and interpreted. While
analysis calls for the use of various statistical procedures
and methods, the interpretation requires a complete and
detailed knowledge of where and under what conditions the
data were collected, methods utilized, assumptions, time span,
etc. Without this descriptive information, the data collected
are meaningless.
Air quality data must first be validated before analysis
and interpretation can proceed. This should involve:
a. Application of corrections for known
instances of instrument malfunction,
drift, or other deviations from normal
instrument operation.
b. Using various criteria such as looking
for atypical high values, low values
and extreme changes in values for con-
secutive observations. These former
data values (outliers) should be
further analyzed to ascertain their
basis. Steps in handling outliers
include:
Checking for instrument or
coding errors
Checking historical data
Examining meteorological data
Reviewing possible changes in
the environment of the monitoring
site
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31
c. Reporting data values based on the
accuracy and precision inherent in
the instruments and analytical
methodology.
d. Determining the completeness of the
data base. (For the data to be
representative/ samples should be
collected "throughout the time
interval under study rather than
bunched all together.)
e. Developing surrogate procedures for
handling data values below the limits
of detection of the instruments
employed.
Once the data has been completely validated and checked
for supporting descriptive information, various statistical
analyses can be performed. These can range from the calculation
and comparison of means and variances, the development of
frequency distributions, development of wind rose-air pollutant
concentration correlations and isopleth contours to the use
of time series analysis and other trend techniques. There are
various computer based calculation routines and data reporting
programs available from EPA which perform most of the above
analyses. For example, there are various meteorological
programs available in PL-1 that correlate wind speed, wind
direction and pollutant values. Also EPA's SAROAD system can
be utilized to access data for various analysis and reporting
purposes.
Currently there is under development a Comprehensive Data
Handling System which would give State agencies the ability to
perform statistical analysis of their air quality data through
a statewide aerometric data system. This system would utilize
SAROAD formats and editing routines.
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As discussed in Section 2, there are various air quality
data reporting requirements imposed on the States by EPA.
The normal flow of ambient air data (including meteorological
data) is from State and local agencies to the EPA Regional
Offices and then to the National Air Data Branch of the
Monitoring and Data Analysis Division. Data submitted to the
Regional Offices must be in SAROAD* format on either coding
forms, punched cards or magnetic tape.
The Regional Office should transmit the State and local
data to the National Air Data Branch either by wire or mail.
The Branch will process the data through editing programs
and will provide error messages to the Regional Offices. The
Regional Offices are then responsible for correcting errors
through contact with the States. Corrected data is then to
be resubmitted to the Branch for file updating and the
performance of various statistical analyses. Figure 1 details
the data flow process from the State and local Agency source
through the various validation and verification procedures
which are performed by the Branch in conjunction with the
Regional Offices.
*APTD Publications 0663, 0907, 0633
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33
* State and local
Air Quality Data
EPA Regional
Offices
NADB
Data Verification
Procedures
CO
«
u
%
u
§
«
w
— .internal data recording
Instrument calibration,
operation, specifications
. Before and after instrument
readings
Other instruments same
location
_ Similar instruments adjacent
location
_ Meteorological conditions
_ Time-series cycle
Physical site location
Sampling probe location
Figure 1. AIR QUALITY DATA FLOW
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5. AIR QUALITY MONITORING EVALUATION
Regional Office evaluation of State and local air
monitoring programs and data should be based on the factors
and principles discuFsed in the previous sections. Such an
evaluation process must include, as a minimum, consideration
of the following elements:
a. Status and reliability of the air
quality network
Is the network large enough to
ensure adequate coverage of the
Region? Will hot spots be detected?
Are sites properly located with
respect to major sources and height
above ground?
Are episode monitoring sites
identified?
Is the sampling methodology
equivalent to the EPA reference
methods?
Are proper quality control pro-
cedures being utilized?
Are instruments being properly
calibrated on a routine basis?
. Are standard reference materials
being used?
b. Growth and activity of sources during
monitoring periods
How did the industrial and economic
activities change?
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35
Were there significant deviations
in emission patterns?
In what areas did growth take place?
c. Atmospheric characteristics
Was the weather unusually warm or
cold?
What was the average wind speeds and
direction of predominant winds?
What were the frequency and duration
of inversions and stagnations?
d. Laboratory quality control
What sample handling and verification
methods were used?
What are the details of the analytical
method used?
What is the type and source of the
standard reference materials and
samples?
What is the frequency of use of check
samples?
When was the last time the laboratory
participated in an interlaboratory
testing program?
What is the quality and calibration
state of instrumentation?
Does the laboratory have an intra-
'laboratory testing program?
. What is the level and training of
the laboratory personnel?
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36
e. Data analysis
. Have the data been properly validated?
Has descriptive information been
provided with the data?
Are SAROAD reporting formats being
used?
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