EPA-340/1-75-008
September 1975
Stationary Source Enforcement Series
GUIDELINES FOR ENFORCEMENT
AND SURVEILLANCE OF
m SUPPLEMENTARY CONTROL SYSTEMS
Volumes I & II
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Enforcement
Office of General Enforcement
Washington, D.C. 20460
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FINAL REPORT
GUIDELINES FOR ENFORCEMENT AND
SURVEILLANCE OF
SUPPLEMENTARY CONTROL SYSTEMS
by
R.J. Bryan, P.C. Kochis
J.W. Boyd, M.L. McQueary and R.L. Norton
September 1975
EPA Contract No. 68-02-1390
Project Officer: GEOFFREY GRUBBS
Regional Programs Section
Division of Stationary Source Enforcement
(EG-341)
U.S. Environmental Protection Agency
Washington, D.C.
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This report was furnished to the U.S. Environmental Protection
Agency by Pacific Environmental Services, Inc., Santa Monica, Cali-
fornia in fulfillment of Contract No. 68-02-1390. The contents of
this report are reproduced herein as received from the contractor.
The opinions, findings, and conclusions expressed are those of the
author and not necessarily those of the Environmental Protection
Agency. This document does not constitute an endorsement by the U.S.
Environmental Protection Agency of Supplementary Control Systems (SCS)
or any other dispersion dependent technique for meeting the National
Ambient Air Quality Standards except as provided within the limits
established by EPA regulations.
The Enforcement Technical Guideline series of reports is issued by the
Office of Enforcement, Environmental Protection Agency, to assist the
Regional Offices in activities related to enforcement of implementation
plans, new source emission standards, and hazardous emission standards
to be developed under the Clean Air Act. Copies of Enforcement Technical
Guideline reports are available - as supplies permit - from Air Pollution
Technical Information Center, Environmental Protection Agency, Research
Triangle Park, North Carolina 27711, or may be obtained, for a nominal
cost, from the National Technical Information Service, 5285 Port Royal
Road, Springfield, Virginia 22161.
PUBLICATION No. EPA 340/1-75-008
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FOREWORD
Pacific Environmental Services, Inc. is pleased to submit this
report to the United States Environmental Protection Agency (EPA) in
partial fulfillment of the requirements under Contract No. 68-02-1390
"Preparation of Guideline for Enforcement and Surveillance of Supple-
mentary Control Systems." Volume I of these guidelines provides
guidance to control agencies in their surveillance and enforcement
of proper conditions of operations of an SCS, including suggested
forms for conducting the various inspections or reviews considered
necessary. Volume II provides detailed background information on
inspection and calibration of S0ซ ambient and emission monitors and
meteorological instruments.
We wish to acknowledge the assistance of Mr. Geoffrey Grubbs,
EPA Project Officer in the work associated with this project and in
the preparation of these guidelines.
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GUIDELINES FOR ENFORCEMENT
AND SURVEILLANCE OF
SUPPLEMENTARY CONTROL SYSTE1S
Volume
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TABLE OF CONTENTS - VOLUME I
Section Title Page No.
I INTRODUCTION 1
1.1 Background 1
1.2 Purpose 2
1.3 General Description of a Supplementary Control
System 2
2 SURVEILLANCE AND ENFORCEMENT OF A SUPPLEMENTARY
CONTROL SYSTEM 5
2.1 SCS Violations 5
2.2 Elements of a Supplementary Control System . . 7
2.3 Portable/Mobile Monitors and Additional Methods
of Surveillance 17
3 INSPECTION/REVIEW PROCEDURES 21
3.1 Comprehensive Inspection 21
3.2 Short Inspection 22
3.3 Unannounced Inspection ..... 24
3.4 Reviews 26
4 INSPECTION AND CALIBRATION OF MONITORING EQUIPMENT
AND INSTRUMENTS 31
4.1 Ambient SO- Monitors 31
4.2 Source Emissions Monitors 37
4.3 Meteorological Instruments 41
REFERENCES 45
A. DEFINITIONS , , . A~1
B. INSPECTION FORMS, CHECKLISTS AND SCHEDULES . . . B-l
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LIST OF FIGURES - VOLUME I
Figure No. Title Page No
B-l Comprehensive Inspection - suggested
B-2
B-3
B-4
B-5
B-6
B-7
B-8
B-9
B-10
B-ll
B-12
B-13
B-14
B-15
B-16
inspection forms
Unannounced Inspection - suggested form ....
Short Inspection - suggested form
Review of Periodic Reports (weekly or monthly) .
Information on Individual Control Decision . . .
Evaluation of Control Decisions
Inspection of Ambient SCL Continuous Monitors
Zero and Span Check for Ambient SCL Continuous
Monitors
Multipoint Calibration of Ambient S0_ Continuous
Monitors
Inspection of SO- Continuous Emission Monitoring
Instruments
Calibration and Inspection of Meteorological
Instruments
Comprehensive Inspection - Personnel/ time
Estimates , . . . .
Schedule for Comprehensive Inspection
Personnel/ time Estimates for Unannounced
Inspections and Short Inspections ,
Equipment Required By Control Agency For
Inspection
Maintenance Checklist for Ambient SCL Continuous
Monitor
B-3
B-6
B-8
B-ll
B-12
B-13
B-14
B-15
B-16
B-17
B-18
B-19
B-20
B-21
B-22
B-23
ii
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SECTION I
INTRODUCTION
1.1 BACKGROUND
The Environmental Protection Agency (EPA) has proposed amendments
to 40 CFR Part 51 regulations (Ref. 1) which would allow selective use
of supplementary control systems (SCS) in order to achieve and maintain
National Ambient Air Quality Standards (NAAQS) for SO in cases where
permanent production curtailment, shutdown, or delays in attainment of
the national standards are the only other alternatives.
While these proposed (Sept. 14, 1973) regulations have not been
promulgated, the basic technical concept of SCS may be incorporated in
individual regulations for the control of sulfur oxides. An example
of such a regulation which applies to a specific non-ferrous smelter,
may be found in Referem. 2. Such regulations, promulgated in Part
52 of the Code of Federal Regulations, require the source to apply
all available permanent controls and permit the use of SCS as a tem-
porary means of attaining and maintaining NAAQS for S0? for these
specific sources where plant closure or permanent production curtail-
ment are the only other alternatives.
Procedures are contained in these Part 52 regulations which des-
cribe the steps to be employed by the source operator in making appli-
cation for and in obtaining authority to use an SCS. Guidelines for
Evaluating Supplementary Control Systems (Ref.3) describe the criteria
and guidelines used for evaluating supplementary control systems and
are referenced frequently in the surveillance and enforcement guidelines
for SCS contained herein. Each request for approval to use SCS is
evaluated either: (1) directly by EPA or (2) by the respective state
agency subject to review and final approval by EPA. Once this final
approval has been obtained, the source develops and tests a working
SCS according to a prescribed compliance schedule. On the date
specified in the compliance schedule, the owner or operator of the
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SCS becomes responsible for attaining and maintaining the appropriate
National Ambient Air Quality Standards.
A list of definitions and key terms employed in these guidelines
is shown in Appendix A to Vol. I.
1.2 PURPOSE
These guidelines have been prepared for the use of the U.S.
Environmental Protection Agency, State and local agencies to assist
them in carrying out proper surveillance and enforcement of supple-
mentary control systems (SCS) following the time that individual
source owners first assume complete responsibility for meeting NAAQS
for SO within the area affected by the emissions from the source
(called the designated liability area - DLA).
1.3 GENERAL DESCRIPTION OF A SUPPLEMENTARY CONTROL SYSTEM
Supplementary control systems (SCS) are systems by which stack
emissions of sulfur dioxide (S0_) are curtailed during periods when
meteorological conditions conducive to ground-level concentrations
in excess of the National Ambient Air Quality Standards (NAAQS) exist
or are anticipated. According to established EPA regulations (e.g.
Ref. 2), authority to operate an SCS will be received by the owner
only after extensive efforts on his part which include:
Installation of an emission monitoring system, air quality
monitoring network, meteorological sensing network and
development of a meteorological prediction program for his
facility.
Completion of a 120 day field study to demonstrate that the
above mentioned monitoring networks, in conjunction with other
available continuous emission controls, are in fact capable
of attainment and maintenance of NAAQS for S09 in the designated
liability area.
Preparation and submission for approval of an operational
manual which describes the location and type of all equip-
ment used in the operation of the SCS, the functions and
names of responsible personnel and the specific criteria by
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which the source decides when to curtail emissions and
by what amount.
Nearly every SCS system will employ two methods of controlling
S02 stack emissions: open-loop and closed-loop control. The open-
loop control method is the normal mode of SCS operation in which the
curtailment decision is based primarily on the observation and/or
prediction of atmospheric conditions over the next few hours. The
closed-loop method can be considered an emergency or an override
method of control and is exercised when actual ambient air quality
monitor readings dictate immediate emission curtailment to prevent
violations of NAAQS for SO..
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SECTION 2
SURVEILLANCE AND ENFORCEMENT OF A SUPPLEMENTARY CONTROL SYSTEM
2.1 SCS VIOLATIONS
The primary task of the control agency is to monitor the source
operator's SCS program for its effectiveness and to enforce the
specific requirements of the regulations applicable to a source
operating an approved SCS. Unless otherwise specified in the regu-
lations the source operator is considered to be in violation of SCS
regulations if at any time:
Any National Ambient Air Quality Standard for S0? is exceeded
after the owner or operator of the source assumes responsi-
bility for the maintenance of such standard in the designated
liability area. Any measured excess of a National Ambient
Air Quality Standard for the specified averaging period (i.e.
3 hour, 24 hour or annual) at any monitor in the SCS network
constitutes a violation. Repeated or consecutive excesses
at the same monitor or non-simultaneous excesses at different
monitors are multiple violations.
The designated liability area (DLA) may occasionally change
at a source and accurate information as to its delineation
should be kept on file in the control agency office. The
DLA can be redefined only with prior approval of the control
agency.
Failure to maintain suitable record of measurements and
reports. Measurement records and reports must be in a use-
able format and readily retrievable. The types of information
needed and acceptable formats for data storage should be
approved by the control agency prior to the time that the source
assumes responsibility for meeting NAAQS in the designated
liability area.
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Failure to submit required monthly (or weekly) reports and
summaries to the control agency. This could be extended
to the failure of the SCS operator to telemeter data to the
control agency if this were required.
Failure to notify the control agency of any violation of
NAAQS for SO within 24 hours of the occurrence of such
violation.
Total SO emission limits from the continuous emission con-
trol equipment available at the plant have been exceeded.
The maximum authorized emission limit reflecting the appli-
cation of available control technology will be contained in
the SCS regulation for that source. It will be expressed
either in PPM, Ibs SO /10 BTU or Ibs SO per hour. The
actual SO emissions for the source are calculated using
the test method and averaging time prescribed in the regula-
tions for that source.
Operations of the SCS are not conducted in accordance with
procedures gpecified in the approved operational manual.
These violations include but are not limited to:
1. Failure of the SCS operator to take the appropriate
curtailment action(s) when curtailment criteria specified
in the operational manual are met. Note that the curtail-
ment criteria and corresponding actions are described in the
operational manual and that a failure of the SCS operator to
curtail emissions at the times specified in the manual consti-
tute a violations of the SCS regulations regardless of whether
or not NAAQS have been exceeded.
Some potential SCS applicants have indicated that curtail-
ment actions will be taken in response to specific
directions of a decision-making computer program, thus
reducing the subjectivity involved with curtailment
decisions. In all cases however, the control agency must
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determine if the correct decision was made and if so,
whether it was properly executed. These determinations
involve a comparison of meteorological data, air quality
data and curtailment actions initiated by the source
with the criteria for making such decisions as specified
in the operational manual. Detailed guidance for
evaluating these decisions is presented in Section 2.2
(Control Decisions).
2. Failure of the SCS operator to carry out the continuous
system-upgrade procedures described in the operational
manual. The success of these procedures is measured by
the improvement in reliability of the SCS during the
preceding year and by the improved ability of the source
to avoid repeating ambient air quality violations under
like sets of meteorological and atmospheric conditions.
See Section 2.2 (Upgrade System) for further discussion
and guidance.
3. Modification of the operational manual by the source
operator without prior approval of the control agency.
These modifications include changes of responsible per-
sonnel from those listed in the manual and changes in
threshold values and corresponding curtailment actions.
2.2 ELEMENTS OF A SUPPLEMENTARY CONTROL SYSTEM
An understanding of the basic components of an SCS is essential
to the surveillance and enforcement of an SCS at a source, particu-
larly to the extent that these elements provide indications of non-
compliance with SCS regulations. In this Section each SCS element
is discussed separately and also as it relates to other elements or
factors. The objective of this Section is to provide control agency
personnel with a description of the numerous elements of an SCS and to
provide detailed guidance in the analysis of the most important of
these elements.
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Control Decisions
The control decision element (the point at which a decision is
made in response to changing atmospheric conditions) represents the
heart of an SCS and an understanding of it is essential to any evalua-
of an SCS. A detailed explanation of the various factors involved in
the control decisions for a particular SCS are described in the
operational manual for that source. These factors include:
A description of conditions which, when met, will require a
control decision
Range of control decision alternates which may be expected
for a given set of conditions (e.g. curtailment, shut down,
process change, etc.).
Who is authorized or expected to make such a decision
(by name/title)
Any control decision is therefore capable of a detailed after-
the-fact analysis to determine how well the control decision procedures
specified in the operational manual were actually followed. Analysis
of individual control decisions should be performed during a short
inspection of the source, as described in Section 3.2 of this Volume.
A more meaningful review is conducted during the Comprehensive inspec-
tion (described in Section 3.1) when the control decisions which have
accumulated over a period of time are analyzed for any trends in either
improved or decreased performance.
Instances of reported air quality violations will be a matter of
record in the control agency files and a review of the circumstances
surrounding these violations should be performed. In addition, source
operator records should be examined as a cross check for instances
when threshold values were recorded or when critical meteorological
conditions occurred or were predicted to occur. A determination
should then be made as to what control decision, if any, had been made
and by whom. This decision should be compared to the control decision
criteria specified in the operational manual. Corroborative evidence
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of the occurrence of threshhold values or critical meteorological
conditions should be obtained from control agency ambient monitoring
records and from independent weather stations covering the designated
liability area.
The functional diagram shown in Figure 2-1 is useful in under-
standing the influence of other SCS elements upon the various control
decisions under examination. The evaluation of this element should
be conducted by the most experienced member of the inspection team,
assisted by other members as necessary. It requires a broad knowledge
of all SCS elements, together with an understanding of management
principles. Since the procedures for implementing these control
decisions will have been previously set forth in the operational
manual and approved by the control agency, primary emphasis should be
placed on how well and by whom these procedures were carried out.
One recommended method of accomplishing this is a case by case review
with those persons shown in the operational manual as being responsible
for the control decisions. It is anticipated that the source opera-
tional manual will provide for some type of time and event logbook so
that key steps in these control decisions are made a matter of record.
In the event that such a logbook is not provided for in the source
operational manual, the control agency should require it either by a
revision to the operational manual or by separate written instructions
to the source operator. If any of the personnel shown in the opera-
tional manual as being responsible for control decisions have been
replaced during the period under review, the inspection team should
examine the type of training provided to these replacement personnel
and make a determination as to its effectiveness in the light of any
control decisions which were made by them.
Just as control decisions must be made to curtail emissions,
control decisions must be made to resume normal operations. This type
of control decision should also be evaluated in the manner indicated
above.
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Figure 2-1. Basic Elements and Functions of a Supplementary Control System
i
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Data
Storage
Values
Measured
Threshold '^ AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Operating
Model
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o _ o_
Scheduled
Emission
Rate
Meteorological
Inputs
Actual
Meteorological
Conditions
Time
Delay
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A
A
A
A
A
A
A
A
A
A
A
A A A
Control
Agency
System Upgrade
Closed-Loop Mode A A A A
Open-Loop Mode o o o O
Data Storage
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Air Quality/Air Quality Monitors
Air quality is the measure of concentrations of a designated
pollutant (in this case, SCO in the ambient air, averaged over certain
periods. Air quality monitors are the sampling units employed to
measure this ambient air quality. The first and overriding concern
of the control agency is the determination that a violation of the SO
ambient standards has occurred or that there is a strong likelihood
that it has occurred. The SCS operator has accepted responsibility
for the air quality within a designated liability area and any viola-
tions of the NAAQS therein are his responsibility.
Actual measures of air quality are provided by the source opera-
tor to the control agency via monthly or weekly reports which show the
hour by hour ambient concentrations of all stations in the SCS net-
work. Independent corroborative measurements are obtained from the
ambient monitors operated by or for the control agency. Based on the
experience of agencies now exercising surveillance and enforcement
of supplementary control systems such as the Puget Sound
Air Pollution Control Agency in Tacoma, Washington, and the Texas Air
Control Board in Austin, Texas, it is strongly recommended that the
control agency operate its own monitoring network to complement and
verify the monitoring network operated by a source authorized to use
an SCS.
These ambient air quality monitors employ several different
principles of operation including gas chromatography (with flame
photometric detection), flame photometric, coulometric and colorimetric.
Some conductimetrie instruments will be referred to within the guideline
since they are presently employed by some smelters, although EPA
has not accepted this measurement principle as of the date of this pub-
lication. The ultra portable S0? analyzer referenced in Section. 2.3.2
also employs the conductimetric principle, but this is not considered to
be a disqualifying factor for its intended use. For further back-
ground on ambient monitors see Section 4.1 of Vol. 1 and Section 1
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of Vol, II of these guidelines.
The SCS ambient air quality network at a source includes all per-
manent sampling stations and mobile/portable units described in the
SCS operational manual. The location of these monitors should have
been carefully evaluated prior to acceptance of the SCS, and they
should represent the points of maximum expected ground level concen-
trations of S09. The relocation of any of these monitors by the SCS
operator therefore, constitutes a change in the operational manual
and is not acceptable without prior approval of the control agency.
The source operator's plan of operation of the permanent monitors and
his plan for the operation of portable or mobile ambient air monitors
should also be specified in the operational manual.
In order to ensure that the location of the monitoring stations
are constantly evaluated for optimum detection of maximum ground level
concentrations of S0_, it is recommended that the control agency
conduct periodic surveys with ultra portable S0_ monitors as described
in Section 2.3.2. Observance of high S0_ levels should be investiga-
ted and a determination made as to whether or not a permanent monitor
should be established in that location.
Threshold Values
The closed-loop method of SCS operation can be considered as
an "override" or emergency method of control in which control decisions
are based on real-time measurements by the air quality monitoring
network. An important element in the control decisions made in the
closed-loop mode is the setting of threshold values for real-time
ambient air quality for SO - the idea being that if appropriate
curtailment action is taken when these ambient concentrations are
reached, the Ambient Air Quality Standards will not be exceeded.
These measured threshold values may vary depending on the time of
day or the location of the monitor, etc., and they may include cri-
teria such as the rate of change in measured concentrations at an
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ambient air quality monitor. They will be specified in the operational
manual and it should be noted that the failure of the source operator
to take curtailment action when designated measured threshold values are
reached, constitutes a violation of the requirement to follow the
operational manual.
The open-loop method of SCS operation entails making emission
control decisions based on calculations generated from the operating
model in conjunction with either real-time or projected meteorological
and emission data. It should be noted that in the open-loop method
of control, predicted threshold values may be utilized as a factor in
the operating model and in ensuing control decisions. These predicted
threshold values should be specified as part of the operating model in
the operational manual.
Time Delays
There are two types of time delays that are inherent in the normal
operation of an SCS:
(1) The delay between the time that a control decision is
made and the time that the ensuing curtailment action
is implemented; and
(2) The delay between the time that a curtailment action is
taken and the time that the action has an effect upon
ambient air quality as measured at the ambient air
quality monitors.
In certain cases, these time delays may allow for flexibility in
exercising various options by which the control decisions may be imple-
mented. For example, in order to achieve the require emission limita-
tion for a predicted meteorological condition, TVA provides for a maxi-
mum allowable generation level and the time by which it must be attained.
This feature allows the SCS operator the flexibility of employing the
best option available to him, commensurate with his other responsi-
bilities. Fuel switching for example, from high to low sulfur coal may
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require 6 to 10 hours but may be more desirable than load shifting
under certain circumstances even though the latter may only require
an hour or two.
Those time delays should be specified in the operational manual.
Upgrade System
This single element is in fact a review and evaluation of the
key elements of the SCS with the objective of improving the overall
reliability of the system to maintain NAAQS. It specifically includes
evaluation of the operating model, meteorological prediction methods,
threshold values, delay times, scheduled emission rate and data storage
elements. The relationships between elements displayed in Figure
2-1 should also be examined. The examination of this element will
normally be made only during a comprehensive inspection and is even
broader in scope than that performed on the "control decision" element.
In fact, it should be viewed as a review of the accumulated control
decisions since the last comprehensive inspection, noting especially
trends toward improving or worsening performance of the SCS.
Meteorological Inputs/Actual Meteorological Conditions
Meteorological Inputs include both the observation of certain
meteorological factors at the time of emission release from the stacks
plus the prediction of these parameters, for some time into the future.
These factors are some of the most important inputs to the operating
model in the open-loop mode of SCS operation, since the model depends
upon accurate real-time and predicted meteorological information in
order to yield a control decision which will prevent the air quality
standards from being exceeded.
Continuous meteorological data (wind speed and direction, tempera-
ture, and dew point) should be monitored at two levels in the lower air
layer, e.g., measurements near ground level in a location not affected
by downwash or other types of air flow distortion due to plant buildings
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or other roughness elements, and measurements at the top of the tallest
stack,.- ^.Measurements in the upper, air layer will extend upward for
several thousand feet above the top of the stack and can only be
obtained periodically via remote sensing methods (rawinsondes, pibals,
acoustic soundings, aircraft, etc.). These will provide information
on stability and mixing height.
Upper air layer measurements should be routinely made at least
twice in every 24-hour period (once in the early morning and once in
the afternoon). The Tennessee Valley Authority (TVA) reports that at
locations where SCS type operations are now being conducted, it is
not unusual to have 3 of these measurements performed daily, either
by rawinsonde or by weather aircraft.
A specific requirement of the operational manual is that it
identifies the meteorological situations before and/or during which
the emission rate must be reduced to avoid exceeding short-term NAAQS.
Prominent in such situations are predictions of atmospheric stability,
mixing height and wind direction and speed over the liability area
surrounding the source stack(s). These meteorological predictions play
a key role in thฃ open-loop mode of SCS operation and source operators
should be required to maintain a file of such predictions.
Scheduled Emission Rates/Controlled Emissions
The scheduled emission rate (or rates) for the source are iden-
tified in the operational manual for the designated processes and levels
of operation of the smelter or power plant; the controlled emissions
represent the emission rate(s) resulting from a control decision and
are likewise identified in the operational manual. Any reported or
measured emission rates in excess of those identified in the operational
manual for specific conditions of operation are prima facie evidence
that the operational manual was not followed.
Since the SCS regulations require the applicant to operate a
measurement system for continuously monitoring S0_ emissions and stack
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gas volumetric flow rates in each stack, the control agency must be
provided with access to these readings. The review of these two
elements is done in conjunction with the control decision element
discussed above since the record of controlled emissions for individual
decisions is an integral factor in the evaluation of the effectiveness
of that control decision.
Measurement of these SO- emissions are made by monitors of either
the extractive or non-extractive type and must be continuous (i.e. at
least one sample or reading every 15 minutes). Extractive monitors are
by far the most prevalent at the present time and employ a variety of
operating principles, including:
Colorimetric
Conductimetric
Coulometric
Membrane diffusion potentiometric
SO fluorescent
UV absorption spectroscopic
Non-extractive or in-situ emission monitors employ a principle of opera-
tion which is essentially spectrophotometric in nature. Refer to Section
4.2 of Vol. I and to Section 3 in Vol. II of these guidelines for more
information on both types of emission monitors.
Operating Model
The operating model is best defined as a set of mathematical
equations which relate meteorological inputs, emission rates, source
data and terrain and location factors to current and future ambient air
quality in the vicinity of the source. Since the applicant's operating
model will have undergone careful scrutiny during the evaluation and
preacceptance period, it can be assumed that potentially critical con-
ditions have been accounted for in the model. The model is based on
mathematical theories of atmospheric dispersion and turbulent diffusion
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and relates actual meteorological conditions, stack emission rates,
and stack parameters (e.g. stack height, stack flow rate) to predicted
ground level concentrations of S02 in the vicinity of the source.
The operating model is described in both the background study
report and in the operational manual. The objective of any examina-
tion or review of this element is to determine if any of the para-
meters of the model have changed or if adherence to the conditions and
actions specified by the model has not been effective in maintaining
NAAQS in the designated liability area. The operating model is of
greatest importance during the open-loop method of control since it
determines the maximum allowable SCL emission rate for that source.
Data Storage
Data storage includes the cumulative records on emission rates,
meteorological conditions and predictions, air quality measurements
and control decisions. All such data must be available to the control
agency. Specific records required to be kept by the source operator
are described in the operational manual. In addition and depending
on the type and amount of data which has been transmitted to the con-
trol agency on a weekly, monthly or continuous data telemetry basis,
the control agency will have accumulated a significant amount of in-
formation on, and an understanding of, the source data storage system.
Portions of this data storage system should be examined in varying
degree during the inspections and reviews described in Section 3.
2.3 PORTABLE/MOBILE MONITORS AND ADDITIONAL METHODS OF SURVEILLANCE
2.3.1 Portable/mobile monitors are S0_ monitors not permanently
located within any network. They are used by the source operator
and/or the control agency to:
1. Verify suspected points of high concentrations not being
monitored by permanent stations.
2. Serve as part of the source's monitoring network described
in the operational manual.
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3. Verify source's monitor reading by duplicate siting of
control agency's monitors.
Most of these monitors employ the same principle of operation as the
ambient monitors discussed in Section 2.2 above; others may riot employ
a measurement principle acceptable to EPA, but are inexpensive,
reasonably accurate, easy to operate and serve only as indicators of
potentially high concentrations which must be followed up by,more
extensive monitoring.
It is recommended that the control agency use a number Of por-
table/mobile monitors as an integral part of its surveillance of a
supplementary control system. Complete and accurate data on ambient
concentrations are essential to ensure that NAAQS are attained and
maintained throughout the DLA.
2.3.2 Additional Methods of Surveillance
The monitors permanently sited as part of the source's ai'r'Duality
monitoring network, while yielding information at the points of maxi-
mum expected ground level concentrations, do not provide the control
agency with information on air quality at points between the monitors.
The control agency may therefore find it desirable or necessary to
employ additional or alternative methods of surveillance to those
described above. The remainder of this Section is devoted to a dis-
cussion of these methods for information and for implementation when
feasible. In almost every instance these methods will not provide
sufficient admissible evidence of a violation for penalty assessment
purposes but they are valuable to the control agency as indicators of
potentially high SCL levels where further monitoring should be per-
formed.
Surveys with SO Ultra Portable Analyzers
One alternate method that might be profitably employed by the
control agency would be surveys or periodic patrols with SO Ultra
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Portable Analyzers, The 'Texas Air Control Board has effectively
employed these in methodically surveying a large area rapidly to de-
termine points of high concentrations, Follow-up measurements can
then be taken by bubblers or other equipment to provide firm evidence
of violations of ambient S0_ standards.
Surveys or patrols with portable SCL monitors may be performed
independently at random intervals during the year or they may be
i
performed in conjunction with inspections. Most such patrols can be
performed by one person and a portable monitor, hand carried or using
a motor vehicle, depending on the nature of the terrain and the area
to be covered.
Aerial Surveys
Aerial surveys to determine SO concentrations are often employed
by source operators and by various governmental air pollution control
agencies. In some cases they are employed to examine the areas surround-
ing a source for discolored vegetation and/or to utilize remote sensing
techniques to provide indications of high ground level SCL concentra-
tions. In still other cases, they have been used to measure S0? at
higher levels (e.g. 2000 feet above ground level) with the aid of
portable S0_ monitors. In either case, aerial surveys are important
only insofar as they indicate the need for, and the nature of, further
SCL monitoring at ground levels.
Discolored Vegetation
Large S09 sources have traditionally employed this method of
detecting the results of high SO surface concentrations after an
episode. Complaints are investigated and claims settled on the basis
of visual observation of the vegetation affected, such as a cash crop.
It is difficult to determine whether the effects have been caused by
a high concentration of short duration or by lower concentrations spread
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over a longer period of time.
This may not be considered an important enough method of detec-
tion for the control agency to devote manpower or other resources for
routine patrols for this purpose, but discoloration noticed during
routine inspections or aerial surveys should be investigated as an
indication that excess concentrations of SCL may be appearing in those
areas.
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SECTION 3
INSPECTION/REVIEW PROCEDURES
3.1 COMPREHENSIVE INSPECTION
3.1.1 Introduction
The comprehensive inspection is in many respects the most impor-
tant inspection. This inspection is designed to provide a thorough
evaluation of the operation of the SCS and the operation and mainte-
nance of all related monitoring equipment. It is especially useful
when employed as a part of each required annual review of the source's
use of an SCS and at such other times that the agency desires complete
information on the operation of the SCS. It is expected that the
control agency will require the services of 3 or 4 persons for 2 or 3
days to complete this inspection. (See Figure B-13 for example of
task scheduling).
3.1.2 Preparation for Inspection
Provide notification as required. A two week advance notice
is sufficient to ensure that all necessary measurement records
and other SCS operating data are available to the inspection
team at the time of inspection.
Compile a folder of reports made by the source operator to
the control agency since the last inspection, including re-
ported violation of NAAQS, emission standards or other
violations discussed in Section 2.1 above. Reports in this
folder will serve as a starting point for selection of dates
for which a detailed data review is to be conducted.
If the control agency operates its own ambient monitoring
network in or near the DLA, compile a list of dates on which
these monitors indicated ambient levels in excess of the NAAQS
and of the threshold levels contained in the operational
manual. This list will be used to evaluate and compare
readings with those obtained from source network stations.
Prepare and check out equipment shown in Appendix B, Figure
B-15.
3.1.3 Inspection Procedures
Tasks include:
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Inspect instruments as shown below utilizing step-by-step
procedures from Section 4 and Appendix B.
- Two ambient monitors
- Emission monitors on at least two stacks
- One of each type of meteorological instrument, e.g., wind,
temperature, humidity.
Calibrate monitoring instruments as necessary - See Section 4.
Check for proper location of permanent monitors and review
plan and implementation of mobile monitoring.
Check that the personnel responsible for the operation of the
SCS as designated in the operational manual are present and
are empowered to order emission curtailment actions without
being overridden by upper management.
Check for unreported changes in operational manual.
Check for changes in stack height or authorized use of
stack heaters.
The authorized stack height(s) is (are) shown in the source
operational manual. While it is unlikely that it will have
been changed without the knowledge of the control agency
during the period under review, any changes or contemplated
changes to stack height(s) should be ascertained during this
inspection. A determination should also be made at this time
as to whether the source operator has begun to utilize or plans
to install any stack heaters. Such heaters provide increased
buoyant plume rise and as such could be a technical violation
of the SCS regulation unless approved in the original applica-
tion or in any subsequent revision.
Inspect records (strip charts, log books, computer readouts)
for any in-house reports of emission curtailment actions,
ambient readings in excess of threshold values and NAAQS and
emission rates in excess of those specified in the operational
manual for particular meteorological and air quality situations.
Note: The results of this combined list should be compared
with those contained in the report folder prepared at the con-
trol agency office prior to the inspection. Any differences
should be examined carefully, particularly those which indicate
violations of SCS regulations not reported to the control agency.
An example checklist for this type of inspection is presented
in Figure B-l of Vol. I of this manual.
3.2 SHORT INSPECTION
3.2.1 Introduction
The source operator is required to report any violation of ambient
air quality standards to the control agency within 24 hours. This
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requirement will be an integral part of the SCS regulation and may
also be contained in the source operational manual. On such occasions,
the control agency should conduct a short inspection of the source to
verify the nature and extent of the violation and to determine the exact
causes for the violation. To be most effective, this inspection should
be made as soon as possible after the report of violation has been
received.
In that respect, the inspection will not be as lengthy as the
comprehensive or the unannounced inspection. It is anticipated that
it will be of brief duration (not more than one day) and will be con-
ducted by a small inspection team of 1 or 2 people. Primary focus of
the inspection will be those portions of the operational manual and
the daily routine which may have contributed directly to the occurrence
of the violation.
3.2.2. Preparation
The control agency will have little or no time to prepare for this
inspection. It will be sufficient to briefly review the report of the
last comprehensive inspection and the file of reported violations since
that time. It is recommended that this report and file be taken by the
control agency inspector on his visit to the plant for ready reference.
Depending on the nature of the violation, he should gather together
necessary equipment shown in Figure B-15.
3.2.3. Inspection Procedures
First priority of the inspection should be a review of the primary
.cause of the violation:
failure of the CEC equipment
inadequate or incorrect curtailment action
uncalibrated equipment
Detailed tasks of the inspection team include:
Examine CEC equipment and operating log to determine emission
rates for 24 hours before and after the violation.
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Interview personnel involved in the control decision; verify
that they are among those identified in the operational manual
as authorized to make such decisions.
Compare control decision made with that specified in the
operational manual for the condition in question.
If inspection determines that an emission or ambient moni-
tor may be faulty - inspect that unit and its maintenance
and operating log. Examine strip charts or other record
for the 24 hour period prior to the violation for evidence
of satisfactory operation and to determine if authorized
emission rates or threshold values were exceeded during
that time.
While this inspection is expected to be relatively brief,
the control agency inspector(s) must recognize that a vio-
lation has reportedly occurred and that some type of penal-
ties may result. It is essential therefore, that the
inspection team gather factual evidence on the nature of
the violation and on the circumstances surrounding the
occurrence of the violation in order to support a subse-
quent enforcement action. Figure B-3 of Vol. I is a re-
commended checklist to be used for this type of inspection.
During the course of the inspection, should it appear that
conditions found are indicative of large scale violations
of the procedures specified in the operational manual and in
the SCS regulation, a more detailed inspection approaching
that of the comprehensive type described in Section 3.1
above should be commenced immediately.
3.3 UNANNOUNCED INSPECTION
3.3.1 Introduction
The scope of an unannounced inspection falls between that of the
comprehensive and the short inspections. Its distinguishing feature
is that it be scheduled by the control agency with a minimum of advance
notice.
This inspection is shorter in duration, requires fewer personnel
than the comprehensive inspection and little or no equipment. None of
the in-depth evaluations contained in the comprehensive inspection,
such as the operator's efforts to upgrade the SCS, etc., are considered
appropriate for the unannounced inspection. Since the comprehensive
inspection will be announced well in advance and will presumably show
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the source at its best, it is recommended that the unannounced in-
spection be conducted during a weekend or other period when the source
may be operating under somewhat relaxed conditions.
This inspection should provide the most realistic insight into
such aspects of the source operator's routine SCS procedures as
monitoring equipment maintenance and calibration, availability of
designated personnel for making control decisions, correlation of
production throughput with emission rates and ambient S0_ readings,
status of constant emission control equipment, source operator's data
storage routine, and general evaluation as to control of fugitive
emissions.
The inspection will require the services of 1 or 2 people for
2 days. It is recommended that at least one unannounced inspection
of the source be conducted each year by the control agency.
3.3.2 Preparation
The control agency should prepare a time schedule for the 2 day
period ensuring that the plant inspection and examination of monitors
is scheduled to be done early on the first day. The inspection should
also:
Review the periodic reports on the SCS received from the
source operator for the past 3 to 4 months for evidence of
trends towards progressively higher readings at any monitoring
stations.
Review same records for excessive gaps in readings from ambient
monitors, indicative of downtimes or other malfunctions at
those stations. Any suspect stations should be scheduled for
examination.
Prepare and check out equipment shown in Figure B-15.
3.3.3 Inspection Procedure
Detailed tasks for completion by the inspection team include:
Conduct plant inspection to determine operation of CEC equip-
ment and extent of"fugitive emission control.
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Inspect instruments as shown below utilizing the step-by-
step procedures from Section 4 and Appendix B.
- Two ambient monitors
- One emission monitor
- Two meteorological instruments
Check for proper location of permanent monitors and check
records for downtime.
Determine presence of personnel authorized in the operational
manual to order emission curtailment actions.
Conduct zero and span checks on 2 ambient monitors and 1
emission monitor. If the results of the checks indicate
differences in excess of 10% of those shown on the cali-
bration curve, a multipoint calibration may be required.
In the case of similar errors on the ambient monitors,
faulty calibration of other monitors could be indicated, and
the zero and span check should be extended to two or more
of these monitors. If acceptable data is not obtained from
these checks, full-fledged multipoint calibrations should be
performed immediately by the control agency or scheduled as
early as possible for all the monitors. Normally, a single
point check (90% of the full scale setting) will suffice for
the initial span checks performed during unannounced inspec-
tions.
Inspect records (strip charts, log books, computer readouts)
for randomly selected periods on those instruments appearing
on lists described in Section 3.3.2 above. The objective
of this record search is to determine occurrence of unreported
violations of threshold values, NAAQS or authorized emission ''
rates.
3.4 REVIEWS
3.4.1 Annual review
An annual review is required for each federally approved SCS to
determine if use of the SCS should be continued or denied. The annual
review is conducted by the control agency and requires the services
of 2 or 3 persons for approximately 5 days. The review consists of:
l.y A comprehensive inspection as described in Section 3.1
above to determine if the source owner or operator has
developed and is employing a control program that is effec-
tive in preventing violations of the NAAQS.
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2. An evaluation of the availability of Constant Emission
Control (CEC) technology.
The availability of constant emission control technology
is a prime factor in determining whether or not a source
operator can continue to operate an SCS, As indicated
in Reference 1, appropriate senior officials of the source
will have certified that they have investigated in good
faith the availability of constant emission reduction methods
as a precondition for obtaining approval to operate an SCS.
The source operator is also responsible for providing to
the control agency in the justification document and in the
source operational manual a general description of the re-
search investigations, or demonstrations that th'e owner or
operator will conduct or support for the purpose of develop-
ing constant emission control technology applicable to his
plant or complex. This description must include the re-
sources to be committed, the qualifications of the partici-
pants and a description of the facilities and equipment to
be utilized.
In the case of federally enforceable rules, the determination
as to availability of CEC technology will be made by the
director of the state agency and/or the EPA Administrator.
It will be based on the demonstration of technology which
may be applicable to the case under consideration.
3. An evaluation of the source operator's performance in
following any applicable compliance schedules for the instal-
lation of constant emission controls at the facility.
4. An evaluation of the good faith efforts of the source opera-
tor to follow the stated program for developing new constant
emission reduction procedures which will be adequate to meet
the national standards without the use of SCS. Specific
items which should be examined are:
Review Research Program
Technical progress
Dollars expended
Personnel assigned
Reports
Future Plans
Review Current Operations
Summary of input materials (smelters only)
Sulfur content of coal for combustion (power plants only)
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Equipment operation and problems
Equipment modifications
Control of fugitive emissions
Review Future Plans
Equipment modifications
New equipment
Processing or combustion changes
Material input changes (smelters only)
Changes in sulfur content of combustion coal (power plants
only)
Pollution control systems changes
Changes in fugitive emission handling systems.
In view of the complexity of the subject matter of constant
emission controls, it is strongly recommended that the control agency
-'*>, : "
maintain a continuous effort to keep itself appraised of the changes in
the control technology for SO- emissions and to conscientiously moni-
tor the research and development program of the source operator in
order to ensure that he is keeping abreast of these changes. One way
in which this can be done is for the control agency to maintain a
current file of the technical literature on the subject and of reports
of public hearings and court decisions on related cases. Reference
(3) contains a summary of the background material for this portion
of the review. The control agency should also avail itself of the
SO control technology information and data available through the
appropriate EPA regional office. For specific short term needs of
such information, the control agency may find it necessary to utilize
the services of a consultant.
5. Review of Other Factors Which Resulted in Original SCS Approval
This constitutes a brief review of the conditions which
justified the approval of the original SCS application.
Changes in these conditions may be sufficient cause for
the control agency to deny continued use of the SCS.
Section 3 of Reference 3 contains a description of the
conditions which must be reviewed.
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3.4.2 Review of Periodic Reports
The specific requirements and frequency of submittal of these
reports will be described in the regulations promulgated for each
respective source, but are expected to include:
Hour by hour measurements of ambient air quality,
emissions and meteorological parameters and other
measurements as may be required,
A summary of all places, dates and times when national
(and state, if appropriate) ambient air quality stand-
ards for S02 were exceeded and by what amount.
A summary report describing operations of the .supplementary
control system as defined in the operational manual and
how the system will be improved.
Change of name/function of key personnel
It is anticipated that these reports will be required monthly,
or quarterly, although it is conceivable that the hour by hour measure-
n-? i rv K<^ j- :. ^.. i
ments may be required weekly or more frequently under certain condi-
tions (e.g. when there are increasing numbers of ambient air violations)
The hour by hour measurements should be examined carefully,
particularly to note the frequency of ambient air S09 concentrations
which exceed the threshold level. An increase in the number of these
readings above the threshold values may be one of the first indications
of a slackening of. interest on the part of the source operator to guard
against violations of ambient air standards.
The review of these reports will provide the control agency with
its best information on the routine operation of the source. Reports
should be reviewed as soon after receipt as possible, using forms B-4,
5 and 6 of Volume I. Reports concerning ambient air quality measure-
ments should be reviewed for:
Violations of air quality standards;
Attainment of threshold values as defined in the
source operational manual;
Periods when data were not recorded or submitted
and reasons why.
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Any reports containing SO emission data should be reviewed
for:
Scheduled emission rate - when it has been exceeded and
by what amount;
Periods when data were not recorded or submitted and
reasons why;
Emission estimates for these periods and reasons for
downtime of emission monitors.
Meteorological data should be reviewed for achievement of values
of wind speed, wind direction, mixing height, etc. which are described
in the source operational manual as critical conditions requiring
curtailment of operation.
The summary portion of this report must describe operations of
the SCS for the time period concerned. These operations will include
any control decisions made, and a report of any violations of air
quality standards or of the SCS regulation itself during the period
of the report.
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SECTION 4
INSPECTION AND CALIBRATION OF MONITORING EQUIPMENT AND INSTRUMENTS
Monitoring associated with supplementary control systems can be
grouped into three general categories:
Ambient air monitors for SO,,
Source stack monitors of SO^ emissions
Meteorological instruments
This section describes the general approach to be employed in
the inspection and calibration of each of the three categories of
instrumentation, providing background orientation, recommendations
and rationale for the approaches selected. The step-by-step check-
list for the inspection and calibration of all instrumentation is
included in appropriate subsections below and in Appendix B.
4.1 AMBIENT SO MONITORS
4.1.1 Inspection
Inspection of ambient SO- monitors should be conducted during
each type of inspection described in these guidelines. The most
thorough ones will be made during the comprehensive and unannounced
inspections. For short inspections, only those monitors with expected
high readings need be involved. Suggested calibration procedures for
continuous ambient S09 monitors are contained in "A Guide for the
Evaluation of Atmospheric Analysis" by Dr. P. Mueller et al (Ref. 4)
or later revisions of that manual. Chapter 8 of that manual is
included in Vol. II of this guideline for ready reference. In all
cases, the Federal Reference Method for the Determination of
Sulfur Dioxide in the Atmosphere (Pararosaniline Method) is to be used
whenever the "referee method" is called for in Dr, Mueller's manual.
Regardless of the type monitor used, a general guideline for
examining ambient S0ซ monitors is provided by this check list:
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The shelter must have 1) adequate working room; 2) adequate
heating and air conditioning; 3) sufficient safe storage
for reagents, gases and tools; 4) water, sewer and electri-
city adequate for all instruments and maintenance operations;
5) good housekeeping practices observed.
The sampling probe and manifold must be of a material un-
affected by SO (e.g. borosilicate glass or quartz glass)
and must be kept clean. The height of the probe should
be at least thirty inches above the shelter roof and it
should be qf a, length and diameter such that the volume flow
rate is between 3 and 5 cfm and the mass flow through the mani-
fold is 3 to 5 times greater than the sampling requirements
of all instruments. Finally the shape of the inlet should
be designed to minimize the amount of extraneous material
which is intrpduced into the manifold, e.g. a "candy cane"
or U-shaped intake.
The instruments in use must use a method which has been judged
equivalent to the Federal Reference Method. The monitors must
also meet the suggested performance specifications (Reference
11, p. 8 and p. 39). Equivalent methods are listed on p. 7
of this same manual and include Gas Chromatography (GC)
Flame Photometric Detection (FPD), FPD detection, coulometric
detection and colorimetric detection.
Each monitor should be checked to ensure that:
Exterior of monitor and components are clean;
Plastic and rubber components are leak tight;
Calibrated air flowmeter is providing constant flow;
Calibrated liquid flow pump is providing constant
flow (where applicable);
All scrubbers have been regularly cleaned and refilled;
Fuses are of correct size and functioning;
All valves operate properly and have been cleaned regularly;
Mercury columns in all thermometers are intact;
pH of all reagents is within the accepted range (see
manufacturer's manual);
All cylinders of gases are of acceptable quality;
Operation of recorders has been checked regularly, particularly
for linearity;
All maintenance and calibration logs are available for inspec-
tion as described in Section 3.1.9;
Schedules for maintenance have been kept.
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4.1.2 Calibration
The most important type of calibration for continuous S09
ambient monitors is the dynamic calibration. Prior to performing
this however, a few preliminary operations should be conducted. The
first one should be a precalibration check containing at least three
points to detect any change in the slope of the calibration curve. A
static check may be used as a check on the electronics and optics
of an analyzer if the design so permits, but this type check may not
be substituted for the required dynamic calibration. Finally, a check
should be made of the calibration/maintenance records prior to the per-
formance of a dynamic calibration. A dynamic calibration, as described
below, must be performed at least at the frequency recommended by the
manufacturer. Permanent records of the work done, signed by the staff
performing the calibration and their supervisor, should include all
strip charts,' graphs and calculations made, as well as a thorough
written explanation of the calibration. A list of items which should
be included in this calibration/maintenance record is given on pages
86-81 of the Field Operations Guide for Automatic Air Monitoring Equip-
ment (Ref. 11).
Dynamic Calibration Method for Ambient S0? Monitors
The calibration procedure for continuous S02 monitors recommended
for use is the one published by Dr. Mueller, et. al., in "A Guide for
the Evaluation of Atmospheric Analyzers" (Ref. 4). Section 2 of Vol.
II of this guideline contains a detailed description of calibration
procedures for automated ambient SCL analyzers. The Federal reference
method is to be used wherever the "referee" mephod is called for in
this reference. Specific points in this procedure requiring emphasis
are:
1. The permeation tube should be equilibrated at the constant
temperature to be used for a minimum of twenty-four hours.
2. The constant temperature bath must maintain the temperature
of the air stream within 0.1ฐC and measuring thermometers
must have this precision.
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3. If .permeation tubes are not used, the source and method
of calibration of standard SCL mixture should be. well
documented.
4. Flowmeters should be calibrated at least monthly by an
accepted method; i.e., a soap-film flowmeter for low
flowrates; a wet test meter, a dry test meter, or a
spirometer for flowrates above 10 ft^/hr.
5. The diluent air or Nป should either be free of SC>2, and
other interferents -such as NO or appropriate scrubbers
should be attached to remove them.
6. All reagents should be prepared at the concentrations,
the frequency and the manner prescribed by the Federal
Reference Method, using chemicals of at least ACS Reagent
Grade purity.
7. If the referee method is not used, the permeation tube
must have been gravimetrically calibrated over a minimum
thirty day reaction period.
8. If the referee method is used, a standardization of the
spectrophotometer should be done concurrently with the
calibration. All steps of the reference method must be
conscientiously observed, particularly with regard to the
length of time needed for color development,
9. Multipoint calibration means that six points, including
the zero and span, are determined in replicate.
10. In examining strip charts of the calibration, sufficient
time must have elapsed'for a steady trace to have been
obtained at each concentration measured. The manufacturer's
manual specifies the recommended times which must elapse
before steady traces are achieved at various concentrations.
11. The method of least squares should be used to define the
calibration curve. The standard deviation of the curve
should be calculated and compared with the standard devia-
tion and slope of previous curves.
12. Any conversion factors from chart readings to ppm should be
recorded in the calibration log.
13. If a static check was made, the results should have agreed
within 10% of the results of the dynamic calibration.
4.1.3 Examination of Records from ambient S00 monitors
Examine records to ascertain that sensors have been continuously
operated for sensing ambient air quality standards.
Data records should be available at least on summary sheets and
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on strip charts. The summary sheets, whether they have been prepared
manually or by computer, should contain, as a minimum, hourly averages
and daily maximums. An inspection of data should include the following
items:
1. Prior to inspection, obtain background information sheets
on the local agency (normally the control agency) on
readings obtained from their system. This would include
daily averages, monthly averages, number and dates of days
exceeding threshold values, air quality standards and wind
roses and other relevant meteorological data.
2. At the source, examine reports from the source operated
network for:
a) Amount and frequency of ambient S09 monitor downtime
about one hour per operating day will normally be
required for zero and span checks. These checks
should not be made during the time of day when high
readings are anticipated or indicated.
additional downtime of ambient SO* monitors may re-
sult from normal maintenance of tne monitors.
Explanations should be available in logbooks (to
be discussed.in greater detail in Section 4.2).
Overall, only 5-10% of the possible data should be
lost due to equipment downtime. Maintenance should
be scheduled so that only one monitor is disabled at
any given time. Backup units should be available
for substitute installation whenever a monitor is to
be out of service over twenty-four hours, A multi-
point calibration, as described in the Section 4.1.2
will generally require about eight hours.
b) Internal consistency
Examining the internal consistency of data involves
cracking such factors as an upwind station's readings
being lower than a downwind station's readings for the
same period and adjacent stations having similar read-
ings. The change in consecutive hourly average should
be questioned if data differ by more than a factor of two.
c) Consistency with data provided by the local agency
Examining agreement between local agency data and source
generated data should concentrate on days when high
values would be predicted and days when high values were
observed.
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For an annual check, twenty six days of data are
sufficient (Ref. 14) for each station. Questions
arising on auditing summaries should be answered
by a thorough examination of the appropriate strip
charts- Among items to check on a strip chart are:
zero drift
span drift
o noise level
occurrence of spikes or high value peaks lasting
less than ten minutes
accuracy of measuring the area under all peaks
The permissible limits for drift and noise are de-
fined in Ref. 11, p.8. Peaks of less than ten
minutes duration may not be included in hourly
averages (Ref. 4). Planimetering the area under any
peak is a quick, accurate method of double checking
questioned measurements.
Quality assurance guidelines have been set forth in "Guidelines
for Development of a Quality Assurance Program, Reference Method for
the Determination of Sulfur Dioxide in the Atmopshere," EPA - R4-73-
028d (Ref. 12). The source operator should have a formalized plan
for assessing the validity of data obtained and he should be able to
demonstrate his use of the plan by selecting at least one month of
raw data at random and then proceeding through all data verification
checks.
As an example of data verification checks needed on a daily
basis, the two highest hourly averages or the two most active hours
should be reexamined by someone other than the person who originally
reduced the data. If differences between any original and recalculated
value exceed + 3%, recalculate all hourly averages for that day. If
hourly averages do not correspond to the source's predicted pattern,
e.g., lowest values are obtained during night time hours, highest
values are obtained when inversions are most probable (perhaps between
9 a.m. and 2 p.m.), the auditor should take the necessary steps to
either verify these anomalies or reject them. Rejected data should be
accompanied by the reason, e.g., excessive base line drift, excessive
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noise, power failure, etc, A final daily data report sheet should
be issued and certified accurate by a knowledgeable, responsible
staff member. During a comprehensive inspection these are the steps
the source must be able to show they have followed.
4.2 SOURCE EMISSIONS MONITORS
4.2.1 Inspection
A thorough inspection of at least 2 SO- emission monitors together
with a comprehensive review of all calibration and maintenance records
and schedules should be performed during a comprehensive inspection.
As noted in Section 2.2 there are several monitoring types and several
manufacturers and models within each type. The guidelines which
follow are referenced to the photometric type but similar criteria for
inspection and calibration are applicable to other types of S0ซ
emission monitors as well. Photometric SO analyzers which extract
and filter the gas sample (as opposed to those which have the detec-
tion cells within the stack) have a high degree of reliability and
minimal downtime because the stack gas is confined to the optical
absorption cell. Additionally there are no detection cells which
require regular replacement. Detailed tasks for an inspection
follow: (see Figure B-lti).
Check inlet filter and light source
The frequency of the inlet filter change is determined by
the particulate loading of the source gas and in the case
of high particulate loading, might require changing daily.
The light source should operate for months before replace-
ment is required.
Check Chiller
Besides a filter, an extractive sampling system generally
requires a chiller to condense water vapor from the sample
so its dew point is below the temperature found in the
optical cell of photometric analyzers. Unless carefully
designed, the chiller can become plugged with ice, so a
proven model should be used. Low sampling rates can
occur due to plugging of the chiller or clogging of the
inlet filter. A low sampling fate will degrade response
time.
-37-
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Inspect optical systems
In an inspection for proper operating procedure, one of the
first things to check is the cleanliness of the optical
system. Any dirt on or fogging of the sample cell windows
will degrade performance. The flow rate through the instru-
ment should also be checked to insure that the filter has not
become clogged. If either of these conditions exist, it is
an indication of inadequate maintenance.
Check maintenance logbook
The instrument should have a maintenance logbook and this
should be checked to see that recommended maintenance has
been performed. Calibrations with span gas should be noted
in the log and should correspond with the instruments in-
struction book's recommendation. The span gases should be
checked to determine that they cover the instrument's range
and that the span gases bear certified analyses.
If the instrument has two ranges, notation should be made
on the chart paper anytime the range is changed. An abrupt
change of level on the chart paper without such a notation
should be suspect of an unmarked range change.
Inspect plumbing system of instrument
Since most photometric SO analyzers aspirate their sample
from the source, any leak in the plumbing leading to the
optical cell will cause a low reading. A simple test for
leaks is to plug the sample extractor and draw a vacuum on
the sampling system. A vacuum gauge or manometer attached to
the sampling system can then be observed to see if the system
is leak tight. The sample inlet line should be heat traced
FEP "Teflon" and could collapse if subjected to high vacuum.
For this reason a vacuum of 10 inches of Hg will usually suf-
fice for a leak check.
Verify location of emission sampling point
One important step in the inspection of all extractive types
of continuous SO emission monitors is to determine the loca-
tion of the sampling point to ensure that it is representative
of the average concentration in the duct. As specified in
Reference (11) and elsewhere, the sampling point for monitoring
the concentration of SO emissions must be in the duct at the
centroid of the cross section if the cross sectional area is
less than 4.657 nr (50 ft^) or at a point no closer to the
wall than 0.914m (3 ft) if the cross sectional area is 4.65;
(50 ft ) or more. The monitor sampling point must be in an
-38-
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area of small spatial concentration in the duct. Informa-
tion on the location of the sampling point will be contained
in the log book for the source's emission monitor and should
also be contained in the source operational manual. The
actual location should be physically checked during a compre-
hensive inspection and during any unannounced inspection
where the validity of the SO emission readings may be in
doubt.
This inspection should be performed by an individual who has
had some practical experience in operating, maintaining or inspecting
emission monitoring or ambient monitoring equipment plus some basic
knowledge of optics. It will generally require such an individual
one-half day to perform all the tasks described above for the in-
spection of an emission monitoring system of a source with one stack,
exclusive of any span gas calibration checks which might be observed
by the inspector or performed by him.
A more detailed description of some of these emission monitors
can be found in Ref. 6. The section titled "Continuous Stack Gas
Monitoring" has been excerpted from this manual and is included as
Section 3 in Vol. II of these guidelines.
4.2.2 Calibration
Calibration procedures for continuous SO emission monitors will
be found in the maintenance and operating manuals published by manu-
facturers for their respective products. It is recommended that the
control agency obtain a copy of the manual describing the type or
types of emission monitor(s) employed by the source operator. In
general, however, all extractive S0? emission monitors are calibrated
in the same manner. Span and zero gases are connected to a 3-way T in
the sample conditioning train ahead of any chilling or conditioning
equipment. The stopcock of the T is turned to pass the zero gas first
and when the analyzer has reached a steady reading, it is zeroed
according to the manufacturer's instructions. A span gas which will
give approximately 80% of the full scale reading is then passed into
the T and it will continue to be passed until the analyzer has reached
-39-
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a steady reading. The span of the instruments is then adjusted so
that the analyzer reads the concentration of the pollutant in the span
gas. Additional span gases should then be passed through the system
which will cause the analyzer to read at 20%, 40%, and 60% of full
scale. Any deviation in the readings from the span gas composition
should be noted, and used to plot a correction curve for use in ana-
lyzing the final data. Span gas may be supplied in cylinders with a
certified analysis from the supplier. Note that permeation tubes are
not recommended for the calibration of continuous SO emission moni-
tors.
In the case of the in-situ monitors the calibration is more
difficult, sometimes requiring removal of the monitor from the stack.
Although it may require a special set up, these monitors should be
periodically calibrated with zero and span gases as in the case of
extractive monitors. These in-situ monitors cannot be dynamically
calibrated, but it is possible that they will be acceptable as a means
for continuous S09 emission monitoring at some future date.
As indicated in Ref. 2, the control agency may specify that S0ซ
emission rates must be determined using the referee methods given in
the Federal Register (Vol. 36, No. 247, December 23, 1971) to corro-
borate the rates measured by the continuous SO emission monitor.
Such corroborative checks should be done at the start of the program
and may be required at any time if consistently inaccurate results
are suspected. The test method for continuous SO. emission monitors
(Method 12) has not been promulgated as of the publication of this
guideline, but a modified version of Method 12 has been published in
Ref. 2 and Ref. 5.
Calibration of a typical emission monitor is estimated to require
one half day per monitoring system.
4.2.3 Examination of records
Plant records should be examined to determine that emission
monitors have been continuously operated. For continuous operations,
-40-
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the sensor recorder chart should have a continuous trace. Breaks
in the trace should be labeled as to the nature of the problem.
Emission monitoring equipment downtime should be calculated or esti-
mated from the source operator's log books and should be approximately
2 or 3 percent over a 24 hour operating period. Downtimes above 5
percent should be questioned, together with downtimes which occur
during critical periods (e.g. during or following any curtailment
action).
4.3 METEOROLOGICAL INSTRUMENTS
Meteorological instruments are an integral part of any air moni-
toring program since meteorological data is extremely important for
predicting air quality. Parameters with which to be concerned when
dealing with supplementary control systems are wind speed and direc-
tion, temperature, precipitation, humidity, solar radiation, and the
turbulence characteristics of the atmosphere (which include winds
aloft and temperature lapse rate) to determine the dispersion capa-
bilities of the air in the region.
4.3.1 Inspection
Meteorological instruments vary widely as to function, complexity
and type. A detailed explanation of all the meteorological terms and
measurement instruments discussed in this section and also in Section
2.2 can be found in Ref. 13 and also in Section 4 of Vol. II entitled
"Meteorological Instruments" which is a subsection of a training
manual on atmospheric sampling published by the Air Pollution Training
Institute on the EPA (Course #435).
It is recommended that the inspection of a random sampling of these
instruments be made using the check list in Figure B-ll.
4.3.2 Calibration
Calibration of wind, temperature, and humidity instruments is
usually simple since these instruments are typically not complicated.
-41-
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Wind speed instruments, such as the cup anemometer, are first
calibrated by the manufacturer in a wind tunnel where the wind speed
is known. The instruments are then placed in the field and often are
never recalibrated. It is assumed that if the instrument is running
smoothly, it is producing accurate data. Periodic greasing of the
bearings keeps the anemometer rotating smoothly. Those anemometers
which require it are calibrated with a motor that will rotate the in-
strument at a known speed. The manufacturer should supply data as to
which rotational speeds will correspond to which wind speeds.
Wind direction instruments are easily calibrated when installed.
By turning the wind vane to a known direction heading, the recorder
can be calibrated by determining the directional output of the instru-
ment and making the proper adjustments of the recorder.
The recorders of these instruments can also be calibrated easily
using known voltages as specified in the manufacturers handbook.
By introducing a known voltage, and knowing what the corresponding
output of the recorder should be, the recorder can be properly adjus-
ted.
Radiosonde instruments, for determining temperature, pressure,
humidity and winds aloft, are first calibrated by the manufacturer.
These instruments are also calibrated before being sent aloft. The
radio signal output is sent to the recorder and compared against the
known values. Radiosondes are tracked by theodolites and readings
are taken every thirty seconds to determine wind speed and direction
aloft.
The radiosonde recorder is checked periodically by introducing
a known radio signal to the recorder and comparing the output to the
reference input.
Temperature and humidity instruments are periodically checked
against reference instruments such as a mercury thermometer or a sling
psychrometer.
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4.3.3 Examination of records
Recorder charts are often used as indicators of the instrument
response for calibration purposes. For example, a wind vane that rubs
during rotation can be discovered by checking the charts. Abrupt
changes in the wind direction pattern, appearing as step functions,
are good indicators that unusual frictional forces are involved.
Maintenance steps would then be called for.
Maintenance and calibration procedures are done routinely at
different time intervals, ranging from daily checks to annual checks.
The source operational manual should be checked for the proposed scope
and frequency of these maintenance schedules. Reference 8 contains
suggested calibration schedules and procedures for wind instruments
and Reference 9 contains maintenance schedules and procedures for
radiosonde and rawinsonde equipment. Reference 10 Engineering and
Quality Control Inspections, discusses inspection techniques used by
the National Weather Service.
-43-
Page 44 Blank)
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REFERENCES
1) "Use of Supplementary Control Systems and Implementation of
Secondary Standards", Federal Register.Vol. 38, No. 178,
September 14, 1973 (40 CFR, Part 51).
2) "Nevada SCL Control Strategy" - EPA Promulgated 40 CFR Part 52
regulations - Federal Register, Vol. 40, No. 26, February
6, 1975. (40 FR 5508).
3) "Guidelines for Evaluating Supplementary Control Systems -
EPA - 450/3-75-035 (OAQPS No. 1.2-036) prepared for EPA
by H.E. Cramer & Co.
4) Muller, P.K., &. Tokiwa, E.R. de Vere, W.J. Wehrmeister, T.
Belosky, S. Twiss, M. Imada, "A Guide for the Evaluation
of Atmospheric Analyzers." EPA Contract 68-02-0214, June,
1973.
5) "Standards of Performance for New Stationary Sources - Primary
Copper, Zinc and Lead Smelters." Federal Register, Vol. 39,
No. 201, October 16, 1974.
6) "Source Sampling and Analysis for Gaseous Pollutants." Course
No. 468, Air Pollution Training Institute - National
Environmental Research Center, Vol. 39, No. 235, December
5, 1974.
8) National Oceanic and Atmospheric Administration, Weather Bureau
Engineering Handbook, No. 8 Surface Equipment (EHB-8)
9) National Oceanic and Atmospheric Administration, Instruction Manual
Calibration of Radiosonde Recording Equipment, Engineering
Division Instruction Manual No. 9, (No. 9-415).
10) National Oceanic and Atmospheric Administration, Engineering Quali-
ty Control Inspections, National Weather Service Handbook
No. 12, Publication (EHB-12).
11) "Field Operations Guide for Automatic Air Monitoring Equipment,"
EPA Contract CPA-70-124, October, 1972.
12) "Guidelines for Development of a Quality Assurance Program,
Reference Method for the Determination of Sulfur Dioxide
in the Atmosphere," EPA-R4-73-028d, August, 1973.
13) T.L. Montgomery et al, "A Simplified Technique Used to Evaluate
Atmospheric Dispersion of Emissions from Large Power Plants" -
Journal for Air Pollution Control Association 23 (5): 338-
394, May 1973.
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14) Guidance for Air Quality Monitoring Network Design and Instru-
ment Siting OAQPS No. 1.2-012, U.S. EPA, January, 1974.
-46-
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APPENDIX A
DEFINITIONS
1) Accuracy - The degree of correctness with which the measurement
system yields the value of gas concentration of a sample relative
to the value given by a defined reference method. This accuracy
is expressed in terms of error, which is the difference between
the paired concentration measurements expressed as a percentage
of the mean reference value.
2) Actual meteorological Conditions - The measures of wind speed, wind
direction, stability, mixing height, and other meteorological fac-
tors at the time of emission release,
3) Actual Emission Rates - The emission rate as measured by the in-
stack emission monitors.
4) Air Quality Violation - A single ambient S0_ concentration that
exceeds a National Ambient Air Quality Standard (NAAQS) for SO
at any point within a designated liability area (DLA).
5) Analyzer - That portion of the measurement system which senses the
pollutant gas and generates a signal output that is a function of
the pollutant concentration.
6) Atmospheric Stability - A measure of the degree to which the atmos-
phere resists or enhances vertical motion,
7) Calibration Drift - The change in measurement system output over
a stated time period of normal continuous operation when the pollu-
tant concentration at the time of the measurement is the same known
upscale value.
8) Calibration Error - The difference between the pollutant concentra-
tion indicated by the measurement system and the known concentration
of the test gas mixture.
9) Closed-Loop Control - The SCS operational mode in which emission
control decisions are based on real-time measurements by the air
A-l
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quality monitoring network.
10) Constant Emission Controls (CEC) - Equipment or control systems
which are permanent in nature and except for maintenance downtime
are operating continuously to reduce or eliminate certain types of
pollutants from stack emissions. For SO , these include wet
scrubber systems and single and double absorption sulfuric acid
plants.
11) Control Agency - Agency (local, state or federal) with
responsibility over the source to ensure that the supplementary
control system is operated in such a manner that the NAAQS are
attained and maintained in the vicinity of the source.
12) Control Decision - Decisions, based on either the model predic-
tion or real-time air quality (whichever dictates the lower
emission rate), whether or not to continue with scheduled processes
and their attendant emissions; and if not, how much to curtail the
emission rate.
13) Critical Meteorological Conditions - Those meteorological conditions
which are conducive to excessive ground level pollutant concentra-
tions.
14) Data Recorder - That portion of the measurement system that provides
a permanent record of the output signal in terms of concentration
units.
15) Data Storage - Synchronous records of meteorological conditions,
emission rate, model prediction, measured air quality, and control
decisions available for control agency review and model upgrading.
16) Designated Liability Area - The geographic area where the ambient
air quality is significally affected by emissions from the source.
17) Designated Personnel - Source personnel with responsibilities for
adherence to the requirements of the SCS operational manual,
including enactment of control decisions and to other regulatory
requirements.
18) Dynamic Calibration - A performance test of the entire analyzer
under simulated service conditions in which the response to a
A-2
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calibrating gas over a known concentration range is determined.
When reconciled with a static calibration, dynamic calibration
also serves to verify 1) the correctness of reagent and sample
air flow rates, 2) the efficiency of sample collection, 3) the
integrity of the analyzer's plumbing, and 4) the quality of any
reagents and/or reactants.
19) Fugitive Emissions - Emissions from a source which do not exit from
a stack.
20) Gravimetric Calibration - A method of calibrating losses or gains
on a weight basis. Permeation tubes are originally calibrated
gravimetrically.
21) In-Situ Emission Monitors - Stack emission monitors that will
analyze the flue gas without removal of the flue gas from the
stack.
22) Inversions - A reversal of the normal atmospheric temperature
gradient, thus an increase of temperature of the air with increasing
altitude.
23) Meteorological Inputs - Observations and predictions of the values
of meteorological variables required by the operational model to
determine the degree of control needed to avoid threats to the
national standard (e.g. wind speed, wind direction, stability,
mixing height).
24) Multipoint calibration - A dynamic calibration of an instrument
involving the determination of response of the monitor to pollu-
tant concentrations equivalent to 0%, 10%, 20%, 40%, 60% and 80%
of the instrument's range.
25) Neutral atmospheric conditions - A deviation from the normal
atmospheric temperature gradient where the potential temperature
remains constant with increasing altitude.
26) Noise Level - Spontaneous deviations from a mean output not caused
by input concentration changes,
A-3
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27) Open-Loop Control - The SCS operational mode in which emission
control decisions are based on calculations using the operating
model in conjunction with either real-time or projected meteoro-
logical and emission data.
28) Operating Model - A set of mathematical equations which relates
meteorological inputs, emission rates, source data and terrain
and location factors to current and future ambient air quality
in the vicinity of the source.
29) Operational Period - A minimum period of time over which a measure-
ment system is expected to operate within certain performance
specifications without unscheduled maintenance, repair or adjust-
ment.
30) Planimeter - A mechanical device for determining the area of irregu-
lar figures. The area is determined by tracing the perimeter of
-the irregular figure with the planimeter.
31) Response Time - The time interval from a step change in pollution
concentration at the input to the measurement system to the time at
which 95 percent of the corresponding final value is reached as dis-
played on the measurement system data presentation device.
32) Sampling Interface - That portion of the measurement system that
performs one or more of the following operations: delineation,
acquisition, transportation, and conditioning of a sample of the
source effluent or protection of the analyzer from the hostile
aspects of the sample or source environment.
33) Scheduled Emission Rates - The emission rate which would result
under the currently scheduled processes and levels of operation.
34) Source Operational Manual - The operating manual for the SCS at that
source. It must be submitted by the source and approved by the
control agency. It contains all essential information on the SCS
including a full description of the ambient, emission and meteoro-
logical networks; an identification of meteorological situations
and monitor readings requiring curtailment actions; identification
A-4
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of source personnel involved in control decisions; and a descrip-
tion of the source operator's program for systematically evaluating
and improving his SCS.
35) Span Drift - The change in ihstrument output over a stated period of
unadjusted continuous operation, when the input concentration is a
stated upscale value.
36) Span Gas - A calibrating gas containing a pollutant concentration
equal to some up-scale value, usually 80% of full scale.
37) Stagnation - Little or no mixing of the atmosphere for pollutant
dispersion, usually due to lack of wind.
38) Static Calibration - The determination of the analyzer response
when artificial stimuli such as standard calibrating solutions,
resistors, screens, optical filters, electrical signals, are applied
directly to the analyzer detector. It is a performance test of the
detection and signal presentation components of the instrument and
is primarily applicable to analyzers using colorimetric and conducti-
metric detectors.
39) Temperature Lapse Rate - The rate of change of temperature with
increase in height.
40) Threshold Values - Measured concentration levels somewhat below air
quality standards and/or rates of change of concentrations that
serve as indicators of potential violations of the standard. They
are selected so that a control decision for emission reduction can
be made in sufficient time to prevent air quality standards from
being violated.
41) Time Delays - Time will be required to implement the control deci-
sion, and more time will pass before the reduced emission rate
affects air quality at a distance from the source,
42) Upgrade Systems - A periodic evaluation of all system parameters
(including the operating model, the meteorological prediction
methods, threshold values and other control criteria), based on
A-5
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stored data, with the objective to improve the system's
reliability in maintaining the national standards.
43) Wind Rose - Any one of a class of diagrams to show the distribu-
tion of wind direction experienced at a given location over a
considerable period; it thus shows the prevailing wind direction.
The most common form consists of a circle from which eight or
sixteen lines emanate, one for each compass point. The length
of each line is proportional to the frequency of wind from the
center. Many variations exist. Some indicate the range of wind
speeds from each direction; some relate wind direction with other
weather occurrences.
44) Zero Drift - The change in instrument output over a stated time
period of unadjusted continuous operation, when the input concen-
tration is zero.
45) Zero Gas - A gas containing less than 1 ppm of sulfur dioxide for
an emission monitor and 0.01 ppm for an ambient monitor.
A-6
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Appendix B
Inspection Forms, Checklists and Schedules
A variety of suggested forms, checklists and schedules are included
in this appendix to assist the control agency in performing the tasks
associated with the surveillance and enforcement of supplementary
control systems. These forms and checklists are representative of
the ones required by control agencies and are not intended to cover
all requirements of each individual agency. Explanation of entries
on individual forms are contained in Section 3 of Vol. I.
B-l
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FIGURE NUMBERS
B-l Comprehensive Inspection - suggested inspection forms
B-2 Unannounced Inspection - suggested inspection forms
B-3 Short Inspection - suggested inspection forms
B-4 .Review of periodic reports (weekly or monthly)
B-5 Information on individual control decision
B-6 Evaluation of control decision
B-7 Inspection of ambient S0? continuous monitors
B-8 Zero and Span check for ambient SCL continuous monitors
B-9 Multipoint calibration of ambient SCL continuous monitors
B-10 Inspection of S0? continuous emission monitoring instruments
B-ll Calibration and inspection of meteorological instruments
B-12 Comprehensive Inspection - personnel/time estimates
B-13 Schedule for comprehensive Inspection
B-14 Personnel/time estimates for unannounced inspections and short
inspections
B-15 Equipment required by control agency for inspection
B-16 Maintenance checklist for ambient S09 continuous monitor
B-2
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FIGURE B-l
COMPREHENSIVE INSPECTION - suggested Inspection Form
PLANT DATE
ADDRESS
PLANT CONTACT(S) & TITLE(S)
INSPECTORS
METEOROLOGICAL INPUTS /ACTUAL METEOROLOGICAL CONDITIONS
Check if critical meteorological values were reached. If so, record
values plus dates and times values occurred.
Check for control decisions enacted at time (or before) critical
meteorological values reached. (See Figures B-5 and B-6)
Check meteorological instruments as outlined in Calibration and
Inspection of Meteorological Instruments, (Figure B-ll)
OPERATING MODEL
Check if operating model correctly identified critical atmospheric
conditions.
Check surrounding terrain for variation from original model data due
to construction, grading, excavating, etc.
Determine relative frequency of occurrence of closed-loop mode of
operation.
Verify stack height(s)
SCHEDULED EMISSION RATE
Check charts and records of emission monitoring equipment to determine if
the scheduled emission rate was exceeded (See Figure B-5)
Check emission monitoring instruments as outlined in Figure B-10, Inspec-
tion of SO- Emission Monitoring Instruments.
B-3
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FIGURE B-l (continued)
CONTROL DECISION
Check what control decisions were enacted and what prompted the en-
actment of each decision (see Figure B-6)
Check if authorized or expected personnel made the appropriate control
decision.
TIME DELAYS
Check and record time delays from the acknowledgement of threshold values
to the enactment of control decisions.
Check and record time delays from the enactment of control decisions to
the reduction of the threshold values.
AIR QUALITY
Check charts and data (source and control agency) for any violation of
S09 ambient standards in the designated area. Record dates and
times of all occurrences. Compare against reported SO. standard
violations.
AIR QUALITY MONITORS
Check for relocation of air quality monitors. If monitors have been
relocated, check for justification and evaluation by appropriate
control agency.
Check records of mobile/portable monitors for high readings. Check if
additional monitoring by mobile/portable monitors resulted
from these high readings.
Check ambient SO instruments as outlined in Figure B-7, Inspection of
Ambient SO Continuous Monitors.
THRESHOLD VALUES
Check if appropriate curtailment actions were carried out when ambient
B-4
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FIGURE B-l (continued)
SC^ threshold values were reached. Record dates and times of
threshold values and the corresponding action taken (see Figures
B-5 and B-6)
DATA STORAGE
Check if required records are kept and are in order. Check accumulated
charts and data for completeness. Refer to Subsection 3.1.10
Check accumulated records for trends in the increase or decrease of
emission rates, production rate, ambient SO- levels, etc.
UPGRADE SYSTEM
Check and suggest factors that may be useful in upgrading SCS system.
This may include evaluating the operating model, meteorological pre-
diction methods, threshold values and delay times. Refer to Figure
B-6.
B-5
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FIGURE B-2
UNANNOUNCED INSPECTION - Suggested Form
PLANT DATE
ADDRESS
PLANT CONTACT(S) & TITLE(S)
INSPECTORS
SCHEDULED EMISSION RATE
Check scheduled emission rate and compare to allowable emission rate defined
in the plant's operational manual.
Check emission monitoring instruments as indicated on Figure B-10, Inspection
of SO. Continuous Emission Monitoring Instruments.
CONTROL DECISIONS
Check if authorized or expected personnel made the appropriate control
decision.
Check control decisions made. Record decisions, dates and personnel
responsible for decision. Compare with decisions required. (See
Figure B-6).
METEOROLOGICAL INPUTS
Check and report upon the condition of the meteorological instruments.
Figure B-ll, Calibration and Inspection of Meteorological Instru-
ments, can be used. (Inspection need not be as extensive as in
other reviews.)
AIR QUALITY
Check charts and data (source and control agency) of SO- instruments to
determine if any violation of ambient standards has occurred.
Check air monitors as outlined in Figure B-7, Inspection of Ambient SO
Continuous Monitors.
B-6
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FIGURE B-2 (Continued)
THRESHOLD VALUES
Check charts and records for approach or attainment of threshold values.
Record control decisions enacted to avoid threshold values and
comment on their actual effectiveness. (See Figure B-6).
DATA STORAGE
Check data and records for completeness. Check accumulated data for
availability and ensure data is up to date.
B-7
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FIGURE B-3
SHORT INSPECTION - Suggested Form
PLANT DATE
ADDRESS
PLANT CONTACT(S) & TITLE(S)
INSPECTORS
Describe nature of violation including date, time and duration of occurrence.
SCHEDULED EMISSION RATES
Check scheduled emission rate for exceeding allowable rate defined in the
plant's operation manual. Record actual emission rate and compare
to allowed emission rate.
CONTROL DECISION
Check control decision and factor(s) prompting each control decision. Com-
pare these control decisions to required control decisions to attempt
to determine cause of violation. (See Figure B-6).
METEOROLOGICAL INPUTS
Check meteorological data for critical values approached before notice of
violation. Check control decision(s) enacted.
TIME DELAYS
Check time delay from the notification of critical or threshold values to
the enactment of the corresponding control decision.
Check time delay from the enactment of the control decision to the reduction
of the threshold values.
AIR QUALITY
Check air qi __
Continuous Monitors, Figure B-7- At a time of violation emphasis should
Check air quality instruments as outlined in Inspection of Ambient SO
B-8
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FIGURE B-3 (Continued)
be on the data. It may not be necessary to even visit any sites
if charts are available in a central location.
THRESHOLD VALUES
Check critical threshold S0ซ values to determine what corresponding control
decisions were enacted (this is an attempt to determine the cause
of the violation). (See Figure B-6).
DATA STORAGE
Check if required records are kept and are in good order. Check accumulated
charts and data for completeness.
B-9
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FIGURE B-3 (Continued)
SHORT INSPECTION - Suggested Form
PLANT
LOCATION
MANAGER
VIOLATION DATE
INSPECTION DATE
OTHER RESPONSIBLE
STAFF
_ HOURS
HOURS
COMPLAINTANT
INSPECTORS
STANDARDS VIOLATED
AMBIENT MONITORS
RECORDING VIOLATION
AGENCY
LOCATION
SOURCE
TIME
VALUE
OTHER INDICATIONS OF EXCESSIVE EMISSIONS
METEOROLOGY
WIND DIR.
WIND SPEED
TEMP.
R.H.
OTHER
SOURCE EXPLANATION FOR EXCESSIVE EMISSION
REMEDIAL ACTION TAKEN
VIOLATIONS INCURRED
(Attach copies of data from all ambient air monitors showing threshold values
of SO to have been exceeded).
B-10
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FIGURE B-4
SCHEDULED REPORTS (WEEKLY OR MONTHLY) - Suggested Contents
The following subjects should be covered in the weekly (or monthly)
reports:
SCHEDULED EMISSION RATE
Discussion and data should be supplied to show that the allowable emission
rate, defined in the operators manual, has not been exceeded.
Information on any problems or non-routine maintenance that must be per-
formed on the emission monitors should be supplied.
CONTROL DECISIONS
Information should be included concerning any control decisions that were
made since the previous report period. Information on the factors
that preceded the control decision should also be included.
AIR QUALITY
Data on the approachment of the ambient air quality standards should be
supplied (high and low values for the report period, mean value
etc.)
Information on any drastic or non-routine maintenance of the air quality
monitoring instruments should be included.
THRESHOLD VALUES
Any approach or attainment of defined threshold values should be discussed.
The control decisions enacted to avoid these threshold values
should also be included.
DATA STORAGE
Data should be included to show that records are being kept up to date and
in good order. Accumulated records should also be shown to be in
order.
B-ll
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FIGURE B-5
INFORMATION ON INDIVIDUAL CONTROL DECISIONS
1. RECEIPT OF ACTION INFORMATION (DATE & TIME)
Critical Meteorological Conditions Predicted
Critical Meteorological Conditions Reached
Threshold Levels of Ambient S0?
Concentrations Attained
S0_ Emissions in Excess of Authorized Rate
Other (e.g. sulfuric acid plant failure, etc, - Describe
2. ACTION TAKEN TIME WHEN ORDERED BY WHOM
Curtailment
Load Shift
Fuel Change
Other (Described)
3. ACTION COMPLETED
4. LEVELS REACHED MAX. READING STATION # TIME
Emission Levels Reached
Ambient Levels Reached
5. NORMAL OPERATIONS RESUMED TIME WHEN ORDERED BY WHOM TIME WHEN NORMAL
LEVEL ATTAINED
6. COMMENTS
B-12
-------
FIGURE B-6
EVALUATION OF CONTROL DECISIONS
Suggested Form
Dates Predicted
Critical
Meteorological
Values
Observed
Dates Air
Quality
Standards
Exceeded
Control Decision Ordered
(describe)
Results
Responsible
Personnel
Evaluation of
Control
Decision
-------
FIGURE B-7
SUGGESTED FORM: INSPECTION OF AMBIENT AIR QUALITY MONITORING
INSTRUMENT.
PLANT: DATE:
ADDRESS: INSPECTOR:
CONTACT: TITLE:
MONITOR:
Site Instrument Principle of Operation
1. Check cleanliness of shelter, monitor, components, recorder and probe
2. Check heating and cooling of shelters for adequacy
3. Check condition of valves and related components
4. Check condition of all tubing
5. Check condition of all air scrubbers and filters
6. Check calibration frequency of air flowmeter
7. Check constancy of air flow
8. Check calibration frequency of liquid flow pump where applicable
9. Check constancy of liquid flow where applicable
10. Check condition of all reagents: age, storage, care of hazardous
chemicals, etc.
11. Check source of gases and certification of analyses
12. Check settings of instruments against settings recorded in last calibration
13. Check format, content and completeness of logbook
14. Check frequency of zero and span checks
15. Check strip charts for excessive baseline drift and noise
16. Check strip charts for readings exceeding threshold values and/or
standards
17. If necessary, perform zero and span checks and/or multipoint calibration
of instruments (see attached form).
B-14
-------
FIGURE B-8
S0_2 CONTINUOUS AMBIENT MONITOR ZERO AND SPAN CHECK - Suggested Form
INSTRUMENT DATE
LOCATION ANALYST
PLANT
ADDRESS
INSTRUMENT SETTINGS
RANGE AIR FLOW
BASELINE LIQUID FLOW
CONVERSION FACTOR FROM RECORDER READING TO PPM
ZERO CHECK
ZERO READING
DIFFERENCE FROM ORIGINAL SETTING
ACCEPTABLE ZERO (YES OR NO)
SPAN CHECK
SOURCE OF SPAN GAS
CONCENTRATION OF SPAN GAS
RECORDER READING
EQUIVALENT PPM
DIFFERENCE FROM ORIGINAL SETTING
ACCEPTABLE SPAN (YES OR NO)
For unannounced or short inspections.
B-15
-------
FIGURE B-9
S00 CONTINUOUS MONITOR MULTIPOINT CALIBRATION - Suggested Form
2 - - ""r '
INSTRUMENT
LOCATION
PRE-CALIBRATION CHECK
INSTRUMENT SETTINGS
SET AIR FLOW
RANGE
BASELINE
SET LIQUID FLOW
DATE
ANALYST
ACTUAL AIRFLOW
ACTUAL LIQUID FLOW
CONVERSION FACTOR-RECORDER READING TO PPM
INPUT PPM INSTRUMENT READING
PPM
DEVIATION
does deviation exceed 10% Yes/No
CALIBRATION
INSTRUMENT SETTINGS
BASELINE
RANGE
LIQUID FLOW
AIR FLOW
Permeation
Tube Output
Dilution
Airflow
Sample
Gas flow
Sample
Time
Recorder
Reading
so2
Cone.
Absorbance
of Impinger
Sample
so2
Cone.
CALCULATIONS
Attach graph of actual SO concentration vs. Recorder Response. Use
method of least squares to obtain best-fit straight line.
B-16
-------
FIGURE B-10
INSPECTION OF SO CONTINUOUS EMISSION INSTRUMENTS - Suggested Form
PLANT DATE
ADDRESS INSPECTOR
CONTACT TITLE
MONITOR
Site Instrument Principle of Operation
1. Check cleanliness of shelter, monitor, components, recorder and probe
2. Check heating and cooling of shelters for adequacy
3. Check condition of sample conditioner and related components
4. Check condition of all tubing" for condensation and loose fittings
5. Check condition of all particulate filters
6. Check calibration frequency of sample flowmeter
7. Check constancy of sample flow
8. Check for proper location of sampling point for monitoring emissions
9. Check calibration of frequency of liquid flow pump where applicable
10. Check constancy of liquid flow where applicable
11. Check condition of all reagents: age, storage, care of hazardous chemicals, etc.
12. Check source of zero and calibration gases and certification of analyses
13. Check settings of instruments against settings recorded in last calibration
14. Check format, content and completeness of logbook
15. Check frequency of use of zero and span checks
16. Check strip charts for excessive baseline drift and noise
17. Check strip charts for readings exceeding threshold values and/or standards
18. If analyzer has dual range, check strip charts to see that the range used
is indicated on chart.
19. Perform zero and span checks and/or multipoint calibration to detect leaks in
sampling system.
B-17
-------
FIGURE B-ll
CALIBRATION AND INSPECTION OF METEOROLOGICAL INSTRUMENTS - Suggested Form
PLANT DATE
ADDRESS
PLANT CONTACT(S) & TITLE(S)
INSPECTORS
INSTRUMENT INSPECTION
1. Check wind speed instruments for smooth rotation; check date of last time
bearings were lubricated.
2. Check wind vanes for frictional errors
3. .Check temperature recording devices with a mercury thermometer
4. Check humidity recording devices with a sling psychrometer
5. Describe any errors determined during calibration check
DATA INSPECTION
1. Check all charts for continuous instrument operation
2. Check wind charts for smooth transition curves
3. Check log book for adherence to calibration and maintenance schedules
4. Check charts and record corresponding dates on the occurrences of
critical meteorological values (See Figure B-6)
5. Describe any variations from expected data values.
B-18
-------
FIGURE B-12
COMPREHENSIVE INSPECTION - personnel/time estimates
2 Men - 2 days - Calibration Team (Maybe 1 man 2^ days)
1) Air Monitor Calibration - (assume 2 instruments) 1 day/instrument
2) Source Monitor (assume 1 instrument) 1 day (or % day)/instrument
Inspection Team 4 Men
Source Monitor Records
Ambient Monitor Records
Data Storage System
Operations Log Book
Plant Inspections
Control Decision Evaluations
Schedules Emission Rate
Meteorological Records
Operations Log Book
Upgrade System
4 Men 2 days
1 Man 1 Day (1)
1 Man 1 Day (2)
1 Man 1% Days (3)
1 Man 1% Days (4)
4 Men h Day (1) (2) (3) (4)
NOTE;
Numbers in parenthesis above refer to personnel of inspection team; i.e.
member number 1 is (1) etc.
B-19
-------
FIGURE B-13
SCHEDULE FOR COMPREHENSIVE INSPECTION
Two Man
Calibration
Source Monitor Records
Ambient Monitor Records
Data Storage System
Operation Log Books
Plant Inspection
Control Decision Form
Scheduled Emission Rate
Meteor. Records
Upgrade System
Air Monitor Calibration
Source Monitor Calibration
Note; Lines represent typical time intervals necessary for individual
tasks. Some tasks such as the inspection of operation log books and
completion of control decision forms can be carried on simultaneously.
Also if permeation tubes are used for calibration of air monitors, they
must be equilibrated in each location for a period of time before they
can be used. During such "waiting" periods, that particular inspector
can be utilized for inspection of records or other tasks.
B-20
-------
FIGURE B-14
Personnel/ time estimates
1. UNANNOUNCED INSPECTION
2 Men - 2 Days
Scheduled Emission Rate & Emission Monitors 1 Man, 1 Day (1)
Air Quality & Monitors & Records 1 Man, 1 Day (1)
Threshold Values ) , , ..
Datastorage 1 Man, 1 Day (2)
Meteorological Data & Instruments ) 1 , _ ,.
Control Decisions > L ***,! Day (2)
2. SHORT INSPECTION
2 Men - 1 Day
Control Decisions I 1 Man,lg Day (1)
Time Delays j
Air Quality Monitors and records
Scheduled emission & Emission Monitors > 1 Man,l Day (2)
Meteorological data and monitors
i 1 Man A Day (1)
Threshold Values (
NOTE:
Numbers in parenthesis above refer to personnel of inspection team;
i.e. member number 1 is (1) etc.
B-21
-------
FIGURE B-15
Equipment required by control agency for inspections
Comprehens ive
Short
Unannounced
Permeation tube x
Dilution Board x
Zero Gas x
Span Gas x
Diluent Gas x
Solutions x
Spectrophotometer x
Portable S0? Analyzer x
Planimeter x
Tubing for Connec-
tions and sampling
lines x
Voltage meters x
Tool Kit x
Mercury Thermometer x
Sling Psychrometer x
Compass x
Stop Watch x
Thermocouple #
Pitot tube #
x
X
X
X
X
X
X
X
X
X
X
X
X
# Required if stack emission rate is in question.
% If calibration of equipment is performed.
B-22
-------
Page 1 of 3
FIGURE B-16
MAINTENANCE CHECKLIST
LEEDS & NORTHRUP AEROSCAN SULFUR DIOXIDE MONITOR
Serial No.
Item
Description
Check
v Date
Technician
1. Prior to maintenance, check the instrument as it was
used in the field:
Calibration check after months in
the field.
Instrument read pphm when it
should have read
pphm.
Percent of error =
10
2. All glassware has heen cleaned in chromic acid.
3. Flowmeter has been cleaned in alcohol
4. All rubber tubing connections have been replaced.
5. All tubing has been cleaned or replaced. Stopper
is in good condition
6. Conductivity cells have been re-platinized according
to correct procedure.
7. Conductivity cells have been checked on bridge and
matched.
#1 = mhos, #2 = mhos.
8. Zero control solenoid has been disassembled and
cleaned.
9. Air flow control assembly has been disassembled
and cleaned.
10. There are no brass fittings between the inlet line
and internal glassware
11. Pump has been disassembled, checked for wear, cleaned,
lubricated and worn parts replaced.
B-23
-------
L & N Aeroscan Sulfur Dioxide Monitor
Page 2 of 3
Check
Item
Description
Date Technician
12. Soda lime scrubber has been cleaned and refilled
/
13. Cabinet interior and exterior is clean
14. Fuses have been inspected and are of proper size.
Amplifier = .5 amp., Sigma pump = .6 and 1.0 amp.
15. Meter reads 0 when instrument is off
16. All five switches function properly
17. Zero control solenoid has been checked for leaks
18. Cabinet fan operates smoothly
19. Air line valve operates smoothly
20. Instrument air bypass valve has been disassembled and
cleaned
21. Air flow has been checked at 40, 60, and 80 on flow-
meter. Curve is drawn, set point for 4.7 l/min.=
on flowmeter.
22. Liquid flow has been checked at 50, 75, 100%, and
curve drawn. Set point for 1.5 ml =
23. Liquid flow checked at 100% = n/ .
ml/mm.
24. All indicator lamps are operational
25. Cabinet thermometer mercury column is not separated
26. Instrument chamber temperature is 120 +1 F.
Actual temperature Fฐ
27. Record Check 1 and Check 2 for thirty minutes each.
Check 1 = Check 2 =
> .
B-24
-------
L & N Aeroscan Sulfur Dioxide Monitor
Page 3 of 3
Item
Description
Check
J
Date Technician
28. No bubbles are in the reagent line
29. Instrument has been checked on zero for sixteen hours.
Drift is- less than one percent. Noise level is
(Should be less than 1% with no spikes or deviations)
30. Instrument has been calibrated at about 25%, 50%, 75%,
and 100% of span
31. Instrument has been labeled as to correct air and
liquid flow settings and next calibration date
32. Instrument has been checked on span ,gas for sixteen
hours. Noise level is %. (Should be
less than 3%
33. The following charts have been turned in with the
maintenance check list:
1. Chart showing 16 hours of zero and 16 hours of
span,
2. Chart showing instrument calibration,
3. Chart showing the zero and span check when
the instrument was brought in from the field
34. Analog charts have been cut, in 24-hour periods, from
0000-2400 and are arranged sequentially. Charts are
Identified as follows:
Date (Month, day, year) (Day of week)
"Calibration of L & N Aeroscan,"
Serial No. DOE No.
Pollutant and range
Signature of operator
In addition, all periods for which the data deviates from normal or is invalid has
been explained. A true time position (PST) is marked on each chart daily.
35. REMARKS:
B-25
-------
GUIDELINES FOR ENFORCEMENT
AND SURVEILLANCE OF
SUPPLEMENTARY CONTROL SYSTEMS
Volume II
-------
TABLE OF CONTENTS - VOLUME II
Section Title Page No.
1 PRINCIPLES OF MEASUREMENT EMPLOYED BY VARIOUS
S02 AMBIENT AIR MONITORS 1-1
1.1 Conduc time trie 1-1
1.2 Colorimetric 1-1
1.3 Coulometric 1-2
1.4 Permeable Membrane - Electrochemical
Transducer Analyzer 1-2
1.5 Flame Photometric and Gas Chromatographic
Flame Photometric 1-3
1.6 Fluorescence 1-4
2 CALIBRATION PROCEDURES FOR AUTOMATED AMBIENT
S02 ANALYZERS 2-1
2.0 Origin 2-1
2.1 Principle and Scope 2-1
2.2 Range 2-2
2.3 Interferences 2-4
2.4 Precision, Accuracy and Stability 2-4
2.5 Apparatus 2-5
2.6 Reagents and Gases 2-9
2.7 Spectrophotometer Calibration 2-10
2.8 Dynamic Calibration 2-10
2.9 Static Calibration 2-17
2.10 Reconciling the Static and Dynamic
Calibrations 2-18
2.11 References 2-19
3 CONTINUOUS STACK GAS MONITORING 3-1
3.0 Origin 3-1
3.1 Interfaces and Conditioning 3-1
3.2 Types of Extractive Monitors for S02, H S,
NO , and CO 3-2
3.3 InXSitu Monitoring 3-11
3.4 Data Acquisition 3-15
4 METEOROLOGICAL INSTRUMENTS 4-1
4.0 Origin 4-1
A. Introduction 4-2
B. Wind Instruments 4-2
C. Temperature Lapse Rate 4-21
D. The Measurement of Secondary Meteorolo-
gical Parameters 4-24
REFERENCES 4~28
-------
LIST OF FIGURES - VOLUME II
Figure No. Title Page No.
2-1 Gas Generating System for Calibrating S02
Analyzers < 2-3
2-2 Sampling Train for Referee SO Analysis 2-8
2-3 Calibrating Solution Dispenser '. . 2-13
3-1 "ECOSTATION" for Measuring a Single Pollutant 3-4
3-2 Optical and Detection System of Nondispersive
Analyzer 3-6
3-3 Operating Principle and Typical Output of a DuPont
Spectrophotometer 3-8
XXIII-1 3-Cup Anemometer . . 4-5
i , i.
XXIII-2 Propeller Anemometer 4-7
XXIII-3 UVW Anemometer 4-9
.' .. . OB ;*?, <;.L,
XXIII-4 Interrupted Light Beam Transducer 4-11
XXIII-5 Wind Direction Sensor - Exterior View and Schematic . . . 4-13
XXIII-6 Axiometer Wind Transmitter - Bivane 4-15
XXIII-7 Dual Pen Recorder Chart 4-17
XXIII-8 540ฐ Recorder Chart ..... 4-17
ii
-------
SECTION 1
PRINCIPLES OF MEASUREMENT EMPLOYED
BY VARIOUS S02 AMBIENT AIR MONITORS
1.1 CONDUCTIMETRIC
This method measures the SO concentration in ambient air by bubbling
the air into a conductivity cell containing dilute hydrogen peroxide or
deionized water. In the instruments using hydrogen peroxide, the SO
is absorbed by the solution and oxidized to sulfuric acid. Sulfuric
acid completely ionizes in solution to form the highly conductive species
H and HSO,~. The presence of these ions in the absorbing solution will
change its conductivity and an electrical signal proportional to the amount
of S09 absorbed will be measured. The instruments using deionized water
as an absorber convert the S02 to sulfurous acid which is a weak conductor.
The conductivity of sulfurous acid is enough to operate a conductivity
cell but not strong enough to be distinguished from the carbonic acid, a
weak acid, formed by CO- absorbed from the ambient air. For this reason
the SO must periodically be scrubbed from the incoming air in order to
obtain a background reading for comparison. This disadvantage must be
weighed against the fact that the deionized water S02 monitors will
operate for extended periods of time unattended, while the hydrogen
peroxide monitors require frequent replenishment of the hydrogen peroxide.
However, both types of instruments are susceptible to interferences
and erroneous readings caused by other gases such as H2S and NH3 which
will dissolve in the absorbing reagent. For this reason conductimetric
measurement of SO, in ambient air has largely been superceded by more
specific methods.
1.2 COLORIMETRIC
Colorimetric ambient air S02 monitors are usually an automated ver-
sion of the pararosaniline method (usually by the West-Gaeke method) for
1-1
-------
determining SCL in ambient air. Although the latter method is quite accept-
able when performed manually in the laboratory, the automation of it is
cumbersome. In particular it requires sequential coupling of an air bubbler,
reagent addition and color development delay tube, and a colorimeter.
Instruments operating on this principle have as yet to demonstrate a
satisfactory degree of reliability. Additionally, considerable quantities
of waste reagent containing a toxic mercury salt are generated. For these
reasons colorimetric monitors for SCL in ambient air have largely been
replaced by other methods.
1.3 COULOMETRIC
The two most commonly used coulometric monitors for S0_ in ambient
air operate as follows. The sample is bubbled through a solution of
either iodine/potassiumiodide or bromine/potassium bromide with the SCL
'f-.J'i.'VK, ;^-J
being oxidized to sulfuric acid by the free iodine or bromine. At the
sample cell anode the current is regulated to generate a constant concen-
tration of iodine or bromine. As SCL reacts with the free halogen, addi-
tional current is required to maintain the original halogen concentration.
This current is dependent upon the concentration of SCL in the ambient
air. The measured magnitude of the current is converted to an output
signal which is directly proportional to the SCL concentration in the
ambient air. These instruments have a good reputation for reliability
and only require maintenance on a weekly to quarterly basis, depending
on the make.
1.4 PERMEABLE MEMBRANE - ELECTROCHEMICAL TRANSDUCER ANALYZER
These SO monitors operate on a principle of first diffusing the SO,,
through a selective semi-permeable membrane and then oxidizing it at an
electrode surrounded by solid electrolyte. The manufacturers of this
type of monitor treat the details of the membrane and electrode construc-
tion as proprietary information; therefore, a detailed description of the
1-2
-------
mode of operation is not presently available. However, their instruments
have a record of successful operation in the field over the past several
years. The membrane electrode sensor is packaged separately from its signal
conditioning amplifier and'is replaced on exhaustion. This is generally
necessary at three to six month intervals, depending on the SO concentra-
tion being measured. One special characteristic of these sensors is that
they will not withstand a negative pressure; therefore, the sample must
be supplied to them by a positive pressure pumping system. The manufac-
turers of this type of sensor make "Teflon" lined pumping and sampling
systems which meet this requirement without degrading the sample.
1.5 FLAME PHOTOMETRIC AND GAS CHROMATOGRAPHIC FLAME PHOTOMETRIC
The principle of operation of the flame photometric SO monitor is
to combust a sample of ambient air in an atmosphere of hydrogen. Any
sulfur compounds present have the sulfur reduced to an excited atomic
state by the hydrogen atmosphere. The excited sulfur very rapidly decays
to the normal state and emits a photon of ultraviolet light. An optical
system focuses the flame area through an ultraviolet transparent filter
onto a phototube. The emitted ultraviolet light causes the phototube to
produce an electrical output which is logarithmically proportional to the
amount of sulfur in the ambient air. All sulfur containing gases, not
just S09, give a response. If only S02 is expected to be encountered in
the ambient air, the flame photometric sensor is satisfactory by itself;
if other sulfur containing gases are expected, it is necessary to couple
the flame photometric detector to a gas chromatograph which is capable of
separating the different sulfur compounds. Several manufacturers market
such a combined instrument. The combined instrument will monitor not
only S0?, but also H-S and the lower molecular weight mercaptans. This
advantage is somewhat offset by the extra maintenance and calibration
required for either option.
1-3
-------
1.6 FLUORESCENCE
SO fluorescent analyzers have been developed for monitoring SO
sources and recently at least one manufacturer has begun to offer
ambient instruments which measure SO by this technique.
1-4
-------
SECTION 2
CALIBRATION PROCEDURES FOR AUTOMATED AMBIENT SO ANALYZERS
2.0 ORIGIN
The material which follows is a slightly modified extract of chapter
8 of reference 4 - "A Guide for the Evaluation of Atmospheric Analyzers"
by Dr. P. K. Mueller et al. If the entire document is desired, appropriate
EPA regional office should be contacted, refering to EPA contract 68-02-
0214 of June, 1973. This information will be valuable for review purposes
should control agency personnel desire to observe or perform actual cali-
brations of the ambient S0ซ monitors in the source operator's SCS network.
2.1 PRINCIPLE AND SCOPE
2.1.1 This procedure is for the calibration of continuous atmos-
pheric sulfur dioxide analyzers. The calibration may be of
two types, dynamic and static. The dynamic calibration must
always be done and is performed by determining the analyzer
response to a series of sulfur dioxide (S0_) concentrations.
The dynamic calibration is a performance test of the entire
analyzer under simulated service conditions and is applicable
to all S0ป analyzers. The static calibration is performed by
determining the analyzer response to artificial stimuli such
as standard calibrating solutions, optical filters, screens,
electrical signals, resistors, etc. This calibration is a
test of the detection and signal presentation components only
and is primarily applicable to S0_ analyzers using wet-chemistry
such as colorimetry and conductimetry. It is not a substitute
for the dynamic calibration.
2.1.2 The calibrating gas for the dynamic calibration may be generated
in two ways. The preferred method is by mixing a stream of
2-1
-------
123
SO from an SO permeation apparatus ' ' (Figure 2-1) with
clean air. Alternatively, streams of dilute S02 (50 to 100
O
ppm; 131 to 262 mg/m ) from a cylinder may be mixed with
clean air.
The calibrating gas is sampled simultaneously with the analy-
4
zer and with the referee method to establish the concentra-
tion of the gas. A permeation tube with a known emission
rate can be used as a primary standard (see 2.6.1) source of
S02 gas.
2.1.3 The static calibration is performed by adding known concentra-
tions of a standard reagent to measured volumes of the analy-
zer absorbing solution which provide an effect equivalent to
concentrations of S0~. These solutions are flowed through
the analyzer detector at the actual reagent flow conditions
encountered during normal operation. The analyzer readings
are plotted versus equivalent SO,, concentrations to obtain a
static calibration curve. The instrument variables (e.g.,
air and liquid flow rates) may be adjusted to make the output
response conform to the pollutant concentration or to a simple
multiple or fraction of the concentration in parts per million
o
(ppm) or micrograms per cubic meter (/ig SO /m ) (spanning) .
When a static calibration is not performed, the spanning may
be done during dynamic calibration.
2.2 RANGE
The range of the calibration procedure is determined by that of the
4
referee method . For a 10-liter sample collected in 10 ml of absorbing
solution and measured in a 1.0 inch cuvette, the range is between 0.01
to 10 ppm S02 (0.026 to 26 mg S02/m3).
2-2
-------
Gas mixing
chamber
Sampling manifold
j Referee sampling J
train '
Vent
Soda lime
Charcoal
Ambient air
Particle Air pump Filter
filter
Gas Dilution Apparatus
S02 Source Apparatus
Permeation device
Thermometer-
Constant
temperature bath
(air or water)
Rotameter
Figure 2-1.. Gas generating system for calibrating SC>2 analyzers,
2-3
-------
The measurement range and the sampling rates of continuous SO
analyzers vary greatly depending on the detection methods. The upper
2
limit of the measuring range can vary from 0.2 to 10 ppm (0.52 to 26 mg/m ).
Sampling rates may vary between 0.015 to 5 1/min. A descriptive compilation
of most of the currently available SCL analyzers is given in Reference 5.
2.3 INTERFERENCES
2.3.1 Interferences are a function of the detection principle. S0_
with purity greater than 99.9% is readily available; higher
purities are obtainable when required. Zero air for dilution
must be free of SO and other substances that can potentially
interfere in the analyzer detection principle. Selective
absorbers (drying agents, Ascarite for CO , etc.) can be used
whenever a particular measurement principle requires it.
2.4 PRECISION, ACCURACY, AND STABILITY
2.4.1 With careful work, the coefficient of variation at the 95%
confidence level of the pararosaniline referee method is
4.6% . Careful attention to the details of the method is
critical.
2.4.2 When spanning is possible, any discrepancy between the input
and output may be resolved by adjusting the instrument
output to correspond to the calibrating gas concentration.
Where analyzers have no spanning controls, a correction factor
may be calculated to convert the analyzer readings to SO
concentrations.
2.4.3 A detailed discussion of the various sources of error in the
preparation of calibrating gases is given in Reference 7,
Part I: General Precautions and Techniques. The appreciation
2-4
-------
and minimization of the sources of errors are important to
assure high levels of accuracy and precision.
2.5 APPARATUS
A gas generation system consisting of sources of SO and zero air,
flowmeters, gas mixing chamber, sampling manifold and a sampling train for
referee analysis is needed in the dynamic calibration (Figure 2-1). The
system should be capable of providing calibrating gases between 0.002 to
n
1.0 ppm (0.005 to 2.6 mg S02/m ). The S02 may be furnished from an SO
permeation apparatus or from a cylinder of dilute SO gas.
The components and connecting lines making up the system should be
sized and assembled so that the differences in the gas pressure between
the various components do not exceed 2% overall to prevent errors in flow-
rate measurements. Ball and socket joints are convenient for connections
that are frequently made and broken.
2.5.1 SO Permeation Apparatus: See Figure 2-1. This can also be
purchased.
1. Flowmeters; To measure the flows of zero air (0 to 1
liter/min) over the permeation tube. They should be cali-
brated frequently (monthly) with wet or dry test meters,
soap bubble meter or calibrated rotameter.
2. Temperature-controlled Bath; Maintained at 20 to 30 ฑ0.1ฐC.
It is needed for proper operation of permeation tube 2.6.1.
4 7
The baths described for SO- ' are acceptable.
3. Needle valves; for controlling the rate of gas flows.
Stainless steel type is recommended for S0_.
2-5
-------
4. Thermometer; A laboratory type or other temperature-
measuring device is needed to measure with a precision of
0.1ฐC or better the temperature of the constant-temperature
bath and the zero air (carrier gas) flowing over the
permeation tube.
2.5.2 Gas Dilution Apparatus (when cylinder S0ป is used)
1. Flowmeters; To measure the rate of S0_ and zero air
flow. Calibrate frequently (at least monthly) as indica-
ted in 2.5.1, Item 1.
2. Needle Valves: to control gas flow rates. Stainless
steel types are recommended for S0_.
3. Mixing Chamber; A cylindrical Kjeldahl type connecting
bulb of 200 to 300 ml volume works well. This can also
be fabricated from borosilicate glass as shown in
Figure 2-1.
4. Sampling Manifold; Fabricate from borosilicate glass
(see Figure 2-1). It should contain three or four ports
to permit simultaneous sampling of the calibrating gas
stream with the analyzer(s) and the referee method.
2.5.3 Zero Air Source
The zero air for diluting the calibrating gas should be free
of SO- and substances that will in any way 1) change the
calibrating gas concentrations, 2) interfere in the analyzer
response and 3) interfere in the referee method. The zero air
may be furnished from a cylinder or by filtering ambient air
as indicated in Figure 2-1.
2-6
-------
1. Air pump (for transport of ambient air) - A diaphragm or
carbon vane pump capable of delivering flow rate require-
ments of the total generation system (5 to 10 liters/rain)
is needed. A particle filter should be installed on the
downstream side of carbon vane pumps and is optional for
diaphragm pumps.
2. Filters for Ambient Air; See 2.6.4.
2.5.4 Manual Sampling Train and Apparatus for Referee Analysis;
See Reference 4 and Figure 2-2.
2.5.5 Analytical Balance; A laboratory type with a sensitivity of
10 /ig or better is needed for weighing the permeation tube.
2.5.6 Calibrating Solution Dispenser (for static calibration);
A solution dispenser, consisting of one or two lengths (about
50 cm) of small diameter (about 1.5 mm I.D,) clear polyvinyl-
chloride (PVC) tubing, a plastic anti-syphon device and a
125 ml low-actinic separatory funnel as shown in Figure 2-3,
is used to deliver the calibrating solutions under controlled
flow conditions by means of furnished screw clamp(s) on the
tubing(s). This (hypodermoclysis) set, which is intended for
administering fluids tinder the skin, is inexpensive and can
be purchased from medical supply houses. A similar device
can be fabricated from small diameter plastic tubing, Y
connector and screw clamps.
2.5.7 Apparatus for Static Calibration; refer to the manufacturer's
instructions for a list of the required apparatus.
2.5.8 Absorber (Impingers); All-glass midget impingers are recom-
mended for collecting the samples for referee analysis. See
2-7
-------
I
00
Flowmeter
Flexible tubing
From sampling
manifold
Needle
valve
*" To air pump
Figure 2-2. Sampling train for referee SOo analysis,
-------
Reference 4 for specifications. The impingers may be pur-
chased from glassware suppliers. Two absorbers in series
are needed to insure complete collection of the sample.
Ball-joint connections are recommended for convenience.
2.6 REAGENTS AND GASES
Purity of chemicals - Unless otherwise specified, all reagent
specifications shall conform to the committee on Analytical Reagents
Q
of the American Chemical Society . When such reagents are not avail-
able, ascertain that they do not lessen the accuracy of the determina-
tion.
2.6.1 S0? Permeation Tubes; Permeation tubes containing S0_ are
commercially available in a variety of sizes and permeation
9 10
(emission) rates ' . The rates may be either nominal or
certified. Certification can be done by the supplier at
additional cost or by the user in his own laboratory. To
assure maximum reliability, these tubes should be weighed
regularly (e.g., at least once a month) and just before use.
Certified tubes can also be obtained from the National Bureau
of Standards.
3
2.6.2 Cylinder SC>2 (50-100 ppm; 131-262 mg/m ): This gas mixture
is further diluted to produce the desired concentrations for
calibration. The concentrations produced should never be
considered as primary standard and must always be standardized
by the referee method or compared to the analyzer response
Obtained with a certified S0_ permeation device.
2.6.3 Zero Air: A high-pressure cylinder of synthetic zero air,
or filtered ambient air from an air pump may be used.
2-9
-------
2.6.4 Zero Air Filter; Activated charcoal and soda lime used together
will remove residual S0_ and most interferents from the zero
gas stream. Excessive amounts of nitric oxide in ambient air can
be removed by placing a CrO oxidizer before the soda lime.
2.6.5 Reagents for Referee Method for SO,,; see References 4 and 7.
2.6.6 Reagents for Static Calibration; refer to the manufacturer's
operating instructions for a list of required reagents.
2.7 SPECTROPHOTOMETER CALIBRATION
1. Prepare a series of calibrating solutions containing the equi-
valent of 0.05 to 0.4 Ml SO /ml (i.e., 1,2,3 ml) as described in
4
the manual referee method . Treat the solutions (Ref 4) and
wait 30 minutes for full color development. Determine the absor-
bance of the solutions on the spectrophotometer against reagent
blank.
2. Plot the net absorbance on the vertical axis versus jzl SO /ml on
the horizontal axis of a rectilinear graph paper as a check for
linearity. Calculate the slope b of best-fit curve for the data
using the method of least squares.
2.8 DYNAMIC CALIBRATION
2.8.1 General
1. When a static calibration (2.9) is to be performed on the
analyzer, it should be done before the dynamic to assure
proper operation of its detection and signal presentation
components. The static and dynamic responses may be
compared (reconciled) to verify the proper operation of
2-10
-------
the analyzer and the validity of the calibration. See
2.10 for details.
2. When the analyzer has been operating as a continuous moni-
tor, it is useful to determine its response near the span
level first without changing the span settings (auditing).
When the response is within ฑ10% of the previous calibra-
tion, the calibration is still valid and a new calibration
is not necessary. When the response is greater than ฑ10%
proceed with the complete calibration.
The audit data provide a record of the calibration drift.
Instruments with non-linear response require the full
calibration.
3. The analyzer to be calibrated should be in good operating
condition and installed in accordance with manufacturer's
instructions. Operate the analyzer for at least 24 hr
to warm-up. This 24-hr warm-up period may be shortened
if so stated in the operating instructions. Adjust the air
and reagent flowrates to their recommended rates or to the
rates determined from the static calibration (2.9) data
and verify the rates as described in 2.5.1, Item 1.
4. Record all data only after stable analyzer response has
been attained.
5. Newly prepared SO. permeation tubes may be used after one
day (24 hr) of equilibration at a constant temperature
provided the concentrations produced are established by
the referee method. A minimum of 30 days is required to
establish that the emission rate is stable and before the
emitted concentration can be used as a primary standard.
2-11
-------
The tube should be equilibrated for at least 12 and
preferably 24 hours whenever the temperature is changed
by more than ฑ5ฐC. See Reference 7 for general precau-
tions pertaining to permeation tubes. It is generally
desirable to precondition all SCL gas lines for % to 1
hour by flowing a stream of dilute SO through them.
2.8.2 Procedure
1. Place the gas generation system as close as practical to
the analyzer to prevent losses and to minimize pressure
changes in the analyzer sampling duct. Calculate the air-
flow of the analyzer and add the airflow needed for the
referee analysis (1.0 to 2.0 liter/min.). Add about 10% of
the total to insure an excess. (NOTE: The excess calibra-
ting gas should be vented to a hood or absorbed by a soda
lime trap to avoid exposure to personnel.) In a proper
assembly, connection or disconnection of the analyzer
sampling line should not alter the airflow settings.
2. Generate a flow of zero air equal to the rate determined in
Step 1 above. Pipet the required volume of absorbing
reagent in the impinger (Item 2.5.8) according to the
4
manual referee method . Connect the impinger to the sam-
pling train as shown in Figure 2-3. When a stable analyzer
response is obtained, sample the gas stream from the mani-
fold for 30 minutes at the rate directed in Reference 4.
Transfer the exposed solution to a 25 ml volumetric flask.
Develop the color of the solution in accordance with the
4
referee procedure and read the absorbance at 560 nm.
When the absorbance of the solution is greater than the
blank, continue flushing the gas generation system until
the absorbance obtained is the same as the blank. Inability
2-12
-------
Connect to Analyzer
Solution Cell Inlet
Separatory Funnel
125 ml Cap
Hypodermoclysis Set
Screw Clamp
Connect to Analyzer
Solution Cell Inlet
Flexible
Tubing
Figure 2-3. Calibrating solution dispenser
-------
to obtain a reading equal to the blank indicates inter-
ferents in the zero air. Correct the source of the problem(s)
before proceeding.
Zero the analyzer by adjusting the analyzer controls so
that the output corresponds to zero or the desired reading.
3. Generate an SO- concentration equal to 80 ฑ5% (span gas)
of the full scale reading (0.80 ppm for full scale of 1.0
3 3
ppm; 2.10 mg S02/m for full scale of 2.62 mg/m ). When
the analyzer response is steady, record the analyzer
reading.
4. When a permeation tube system is used and has been shown
by frequent referee analysis to provide reliable SO,., con-
centrations, the collection of referee samples may be
omitted. The S0ป concentrations are calculated from the
diluent gas flow and permeation rates by equation 1 or 2.
a) To determine the concentration of S0? in ppm
from the permeation tube emission rate, use equation 1.
2.62 (Qd)
where P = permeation rate in /zg/min.
Qd = rate of zero (diluent) air in liters/min.
b) When the concentration units are desired in j*g S0_/m
instead of ppm, then:
o
S02/m3 . CP X M^.,. , (2)
2-14
-------
5. To establish, the SO- concentration by referee analysis:
a) Collect duplicate samples of the gas stream and analyze
4
as described in the referee method . Adjust the sam-
pling period to keep the absorbances of the samples at
about midscale (0.3 to 0.5A) on the spectrophotometer.
Five to 30 minutes are usually sufficient. For maxi-
mum precision, place the flasks containing the reacted
solutions in a bath maintained within 2 C of the tem-
perature used during the development of the spectro-
photometer calibrating solutions.
b) From the volume of air sampled and the slope of the
spectrophotometer calibration curve, calculate the
ppm S0_ as directed in equation 3.
where: ppm = concentration (Ml/1) S0_
A = net absorbance of the solution
b = slope of the spectrophotometer calibra-
tion curve obtained in 2.7
V = volume, in liters, of the gas sample
3.
collected (liters/min X min)
To convert ppm to MS/m > use equation 4
jig S02/m3 = ppm S02 X 2620 (4)
Usually, changes in the gas volume of the samples due
to deviation from the standard conditions of 25 C and
760 torr are small and may be neglected. When the
2-15
-------
deviations are large, (sufficient to cause a change in
gas volume greater than about 5%) correction should be
made.
c) The concentrations of the duplicate samples should be
within 5%. Differences greater than 5% may be due to
unstable gas concentrations, errors or inconsistencies
in sample collection and analysis. Correct these
problems before proceeding with the calibration.
6. When possible, adjust the analyzer to give reading equiva-
lent to the span SO concentration (spanning). When the
instrument has no span controls, proceed to Step 7 below.
Generate zero air and note the analyzer reading. When the
reading is different from the original baseline reading by
>2%, reset the analyzer to read the original baseline and
repeat Steps 3 through 6 above. Analyzers with zero and
span controls not electrically independent may have to be
respanned and rezeroed iteratively until the proper zero
and span settings are obtained.
7- Generate, in turn, four additional SCL concentrations
between the blank and span range (e.g., 10, 20, 40, and
60% of full scale) and determine the SO- concentrations in
duplicate and analyze as directed in Steps 3 through 5
above. Determine the net analyzer readings by subtracting
the baseline reading from the individual readings.
2.8.3 Treatment of Dynamic Calibration Data
1. Plot the net analyzer readings on the vertical axis versus
the corresponding SO concentrations on the horizontal
axis of an appropriate graph paper (rectilinear, semi-log,
2-16
-------
log, etc.)- Calculate the slope b^ of the best-fit curve
for the data by the method of least squares. A non-linear
response from an instrument normally linear indicates
analyzer malfunction or, possibly, errors in the prepara-
tion of the calibrating gases. Correct the cause of the
problem(s) before recalibrating.
2. When a non-linear response is normal, draw a smooth line
through the calibration points that fits the points best.
From this, prepare a template to convert the net analyzer
readings to SO,, concentrations.
2.9 STATIC CALIBRATION
The following section pertains to SO analyzers using wet-chemical
methods (colorimetry and conductimetry). See also 2.1.3.
2.9.1 Procedure
Prepare calibrating solutions (equivalent to 10, 20, 40, 60,
and 80% of full scale) and perform the static calibration
according to manufacturer's instructions. In the absence of
such instructions the static calibration procedures described
in Chapter 6 of this manual (Dr. Muellers Manual, SCS Ref. 4
of Vol. I) for automated oxidants and ozone analyzers, may be
used as a guide.
2.9.2 Treatment of Static Calibration Data
1. Plot the net analyzer readings on an appropriate graph
paper (rectilinear, semi-log, etc.) against the equivalent
\i\ S09/ml of the calibrating solutions. Calculate the
slope b of curve that best fits the data by the method of
2-17
-------
least squares. A non-linear response from an instrument
normally linear indicates malfunction in the analyzer or
error in the static calibration process. Correct problem(s)
before recalibrating.
2. When a non-linear response is normal, prepare a template
as directed in Step 2 of 2.8.3., An alternate method is to
attempt to linearize the instument output by adjusting the
electronics (i.e. photometer, etc.) until a linear output
is found over the range of pollutant concentration of
interest.
2.9.3 Determination of Airflow Rate
For instruments not equipped with adjustable upper limit or
span controls or when the range of span adjust is insufficient,
the slope of the static calibration can be used to establish
the sample airflow rate that will make the analyzer output
correspond to the pollutant concentration or a simple fraction
or multiple f of the concentration range as follows:
s
Qa = (Qr> (fs} (5)
(bg)
where: b = slope of the static calibration curve obtained in
S
909
ฃ.ป>ฃ>
Q = analyzer airflow rate, ml/min.
3.
Q = analyzer reagent flow rate, ml/min
f = range factor (e.g., %, 1.0, 2.0)
S
2.10 RECONCILING THE STATIC AND DYNAMIC CALIBRATIONS
The static calibration slope b (2.9.2) and the dynamic calibration
S
2-18
-------
slope b, (2.8.3) are compared by equation 6:
b - b
R = -i-^ ^ X 100 (6)
s
Large values of R (>10%) are indicative of a) error in the analyzer's air
or reagent flowrate; b) leaks or malfunction in the analyzer; c) poor
quality reagents; d) error in the static or dynamic calibration process;
or e) change in the sample collection efficiency of the analyzer. Consult
the analyzer operating instructions and/or manufacturer and correct the
problem(s) before recalibrating.
2.11 REFERENCES
1. O'Keeffe AE, Ortman GC: Primary standards for trace gas analy-
sis. Anal Chem 3_8_: 760, 1966.
2. Scaringelli FP, Frey SA, Saltzman BE: Evaluation of teflon
permeation tubes for use with sulfur dioxide. Amer Ind Hygiene
Assoc J 2A:26Q, 1967.
3. Scaringelli FP, O'Keeffe AE, Rosenberg E, Bell JP: Preparation
of known concentrations of gases and vapors with permeation
devices calibrated gravimetrically. Anal Chem ^2_:871, 1970.
4. Environmental Protection Agency, National primary and secondary
ambient air quality standards, Appendix A: Reference method
for the determination of SO in the atmosphere. Fed Reg 36;
No. 84, Friday, April 30, 1971.
5. Environmental Instrumentation Group, Lawrence Berkeley Laboratory,
Univ. of Calif., Berkeley, Calif.: Instrumentation for environ-
mental monitoring, Air, LBL-1, vol.1 (S02> Dec. 1, 1971.
2-19
-------
6. Pate JB, Ammons BE, Swanson GA, Lodge JP, Jr: Nitrite inter-
ference in spectrophotometric determination of atmospheric
sulfur dioxide. Anal ChemJ37_:942, 1965.
7- Intersociety Committee: Methods of air sampling and analysis.
Amer Publ Health Assoc, 1015 18th St., NW, Wash., DC, 1972.
8. ACS Reagent Chemicals, American Chemical Society Specifications.
American Chemical Society, Washington, B.C. For suggestions on
the testing of reagents not listed by the American Chemical
Society, see: Rosin J: Reagent Chemicals and Standards. New
York, D. Van Nostrand Co., Inc., and the United States Pharma-
copoeia.
9. Metronics Associates, Inc., Palo Alto, CA 94304.
10. Analytical Instrument Development, Inc., 250 South Franklin
Street, Westchester, PA 19380.
11. National Bureau of Standards, Office of Standard Reference Ma-
terials, Washington, DC 20234.
2-20
-------
SECTION 3
CONTINUOUS STACK GAS MONITORING
3.0 ORIGIN
The following material was extracted from a training course given by the
Air Pollution Training Institute of the Environmental Protection Agency. If
the entire document is desired, contact should be made to the Air Pollution
Training Institute, National Environmental Research Center, Research Triangle
Park. The document to request is Course 468 - Source Sampling and Analysis
for Gaseous Pollutants. This section will be a valuable reference when the
control agency finds it necessary to inspect and/or calibrate the emission
monitoring instruments.
3.1 INTERFACES AND CONDITIONING
The interfacing of continuous analyzers and their sample conditioning
requires even more attention than noncontinuous analyses because the former
usually operate over long periods of time unattended. The long periods of
unattended operation increase the chance that plugged filters or condensation
in the sampling line may go unobserved until too late. If this does occur
the information covered by the malfunction time will be irretrievably lost.
The simplest and most direct method of extracting the sample from the
source is to insert a probe, with a filter tip, into a point in the source
where the pollutant being measured is representative in concentration of
the entire discharge. The probe and filter should be constructed of a materi-
al which will withstand the conditions within the source and at the same
time not adsorb any of the pollutant being measured. An example for extracting
SO from a stack would be a stainless steel tube containing a "Pyrex" glass
tube with a plug of "Pyrex" glass wool in the end of the probe. Outside of
the stack the "Pyrex" lining would connect to a heat traced "Teflon" tube
which would lead to the sample conditioner. The heat tracing should be ade-
quate to keep the sample above its dew point.
3-1
-------
The sample conditioner is usually best purchased from the maker of the
continuous analyzer, as he best knows the requirements of his instrument.
It also avoids a situation where one manufacturer could lay the blame for
inadequate performance on the other manufacturer's equipment. However in
the case of multipollutant sampling, it may be more convenient to purchase
a probe sampling line and manifold separately. The various instruments
would then tap into the manifold. In this case assurances should be ob-
tained from the various analyzer manufacturers that their equipment will
operate satisfactorily from such a sample extraction system.
An alternate method of sample extraction has been proposed by C. E.
Rodes in the Oct. 1973 issue of Instrumentation Technology. This method
dilutes the sample with dry air near the probe inlet, and also injects
calibration gas near the same point. If a dilution factor of 10 to 1 or
more is acceptable to the analyzer, this method of sample extraction
obviates most of the problems of sample conditioning. The method does
require accurate control of sample and dilution air flow rates.
3.2 TYPES OF EXTRACTIVE MONITORS FOR SO , H S, NO , AND CO
^ ฃ. X
3.2.1 Electrometric
The Dynasciences Corporation Division of the Whittaker Corpora-
tion* markets SO , NO , N0_ and aldehyde analyzers which
ฃ- X 2.
operate on a permeable membrane, coulometric measurement
system. A wide range of sensors are available which will
cover the concentrations of pollutants found in source stacks
and in ambient air. They also manufacture sample extraction
and conditioning systems designed for operation with their
monitors. The sensing elements of the monitors have an
expected life of 3 to 6 months and then must be replaced.
The expended sensors can be recharged only by the manufacturer.
*Trade names mentioned in this document are for the convenience
of the reader and do not imply endorsement by the U.S.
Environmental Protection Agency
3-2
-------
International Biophysics Corp. of Irvine, Calif, manufactures
a series of sensors for SO H S, NO, NO and NO . These
ฃ* ฃ* ฃf X
sensors operate by polarographically sensing the pollutant
which diffuses through a membrane. The polarographic sensor
and membrane are contained in a special cartridge which plugs
into the amplifier-signal conditioning unit. The response time
on the system is quite fast, in the order of seconds, and
recovery time equally so. International Biophysics Corp. manu-
factures complete sample extraction and conditioning units
which are designed for compatability with their sensors. An
example of an International Biophysics Corp. "EcoStation" for
measuring a single pollutant is shown in Figure 3-1. The
sample chilling unit is continuously blown down and the unit
is stated to maintain sample gas integrity within 2%. Inter-
national Biophysics Corp. sensors are made in ranges which
cover both stack and ambient pollutant monitoring. The sensors
again have a life of 3 to 6 months, after which a new sensor
must be plugged into the signal conditioning unit and the
sensor sent back to the manufacturer for recharging.
The Phillips Electronic Instruments division of Phillips of
Holland markets coulometric analyzers for the measurement of
SO , NO, N0_, CO and KLS. With the exception of the CO monitor,
they operate on the principle of chemically reducing a HBr
solution with the lost HBr being electrolytically regenerated.
The current for the electroregeneration is measured which in
turn gives a measurement of the pollutant. In the case of CO,
I 0 is reduced by the CO and the liberated ! is absorbed and
measured coulometrically. These instruments were designed
primarily for ambient monitoring, and in the case of high
pollutant levels, sample extraction and conditioning by the air
dilution method mentioned on page 2 would be necessary. They
do offer the advantage of operating up to 3 months unattended
3-3
-------
Sir*
-Probe. Assembly Option
Inst. Air
50 PSI
Zero Gas
--H.T. Sam. Line
Option
Vent
" Vent
Enclosure
Customer
Furnished
Figure 3-1. "EcoStation" for Measuring a Single Pollutant
(International Biophysics Corporation)
3-4
-------
as they contain their own calibration source and have automatic
zero and span adjustment.
Theta Sensors, Inc. markets a series of S0~, H S, NO,.,, NO and
NO sensors which operate on the permeable membrane potentio-
metric principle. The individual sensing units are contained
in a signal conditionong panel and will require replacement
after 3 to 6 months. The sensor units must be recharged by
the manufacturer. Theta Sensors, Inc. also manufactures sam-
ple extraction and conditioning units which are designed for
operation with their sensors.
3.2.2 Spectrometric Monitors
Nondispersive infrared S02 and CO monitors are manufactured by
Beckman Instruments, Leeds and Northrup and Mine Safety
Appliance Co. Bendix Instrument Division imports one manufac-
tured in Germany. They all operate on a very similar principle.
Figure 3-2 illustrates the optical and detection system of a
Beckman nondispersive analyzer, which is typical of this
method of measurement. It consists of dual infrared sources
and dual optical absorption cells. One of the latter is
filled with a nonabsorbing gas while the other has the sample
passed through it. A gas microphone, filled with the pollutant
of interest, is placed at the end of the dual optical paths.
A chopper (rotating occluder) alternately blocks and passes
the infrared radiation through the optical system. If the
sample cell contains the same gas as is confined in the gas
microphone, less of the infrared radiation which is absorbed
by the gas in the sample cell will reach the microphone cell
on the sample side. The gas in the sample side microphone
cell will then receive less infrared radiation which it is
capable of absorbing, and will be heated less than the gas in
3-5
-------
Figure 3-2. Optical and Detection System of Nondispersive Analyzer
Non-Absorbing
Molecules
Infrared-Absorbing
Molecules
Chopper Motqr_
Reference Source
<'^|UJ Isample
Chopper
Stationary
Metal ButEoTT
Reference Chamber
Oscillator Unit
Source
Sample In
A. Beams not blocked by
chopper pass through
cells and into detector.
Sample Out
Sample Chamber
Diaphragm
Distended
To Amplifier/Control Section
Chopper Motor
Reference Chopper
Chopper
Sample Source
Stationary
Metal Butto
Reference Chamber
Oscillator
i i
. i
0)
CJ
0)
(J
c
0)
0>
IM
OJ
Crf
==
ฐ o
0 0 ฐ
0 O
o c
ฐo o
o 0ฐc
o
o o
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00ฐ
p77
I* *
Unit
o
o
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HI
^uป
^
1 1
-------
the reference side microphone cell. As the chopper causes the
infrared radiation to be pulsed, this will cause a pulsing
expansion of the gas on the reference side of the microphone
causing the microphone diaphragm to oscillate. The oscillation
will be proportional to the absorbing gas in the sample cell
and is detected electronically.
With appropriate optical filters and gas filling of the micro-
phone, the instrument may be made specific in response to SO-,
NO, NO-, hydrocarbons and CO. However the weakness of non-
dispersive infrared analyzers in source sampling is the degra-
dation of the optics and internal optical coatings due to the
corrosion from SO and NO.. Past experience has indicated that
their performance may fall off in a period as short as a few
weeks if the gas being monitored is corrosive. On the other
hand they are one of the few instruments which will monitor
CO at low levels (down to a few ppm).
Du Pont manufactures a visible-ultraviolet spectrophotometer
which measures both SO and NO continuously and NO at 10
minute intervals. The optics of this spectrophotometer are
much less susceptible to corrosive degradation than the non-
dispersive infrared spectrophotometers as the sample tube is
not internally coated with reflective material. However an
interfacing system must still be employed to prevent particu-
late from entering the instrument, and the dew point of the
sample must be lowered to ambient to prevent condensation in
the spectrophotometer. The operating principle of the Du Pont
Model 400 spectrophotometer is illustrated in Figure 3-3. As
is shown in the plots in the lower half of Figure 3-3, S02 and
NO have well separated absorption peaks in the ultraviolet
and visible portions of the spectrum. S02 has no absorption
and NO- relatively little absorption in the orange part of
3-7
-------
Me a
Pho
\
suring Semi-Transparent Mirror
totube (Beam-Splitter) Callbratlon
\ \ / Filter / Sample
y- ,-|_ V n n r'pi1 r
v. LF- ~<^|i U U I
N "' fy
!!j '"*
Optical 'hi
Filters ', |
~7. \. lill .
/ X ^^"iT13 /-^3-Way ^
Mil / t ValvesL
Log " / Irs^i rjU
Amplifiers .ll||. , ^^J VA^
^1 ^i ' T , I.
^v^ Reference 1 /i
Phototube /
\ CheckJ, at
Span and Zero \ValveX
Controls T
'
Rec
Ou
J
->. ^>-
\~ ' "
360 1 n .
Sampling Ga
' Digital Panel
order Meter (Optional.)
tput F
ack
Optical
/ Filter
1-H1- ffl
^h Jl.
u r^
A" I I
nr Lamp
HT
U
*\
' Outlet
gen ,
60psig/^
^v^~_ Opti
/ NO
/ *
/
s Inlet
2.
1.
1,
1.
1.
1.
0)
u
ง 0,
,0
i 0,
,J3
4
0
0
0
Or
Figure 3.3. Operating Principle and
Typical Output of a DuPont
Spectrophotometer
SO
NO.
578
250 300 350 400 450 500
Wavelength (NM)
3-8
550
600
-------
the spectrum. By using a mercury vapor lamp to generate
light which has strong emission lines at the three wavelengths
shown on the plot, the two pollutants can be measured by
their selective absorption. NO has no absorption in this
spectral region, but is measured by stopping the flow in the
NO^ sample cell, pressurizing it with CL and waiting ten
minutes for the NO to be converted to N0? by the excess
oxygen. The NO is then measured by the difference in the
readings before and after the reaction with oxygen.
The upper half of Figure 3-3 illustrates the operating prin-
ciple of the Du Pont Spectrophotometer. Light from a mercury
vapor lamp is directed down the sample cell. A semi-transparent
mirror passes half the light to the measurement phototube and
at the same time deflects half to the reference phototube.
Narrow bandpass filters pass the 280 nanometer mercury line
(in the case of SO ) or the 436 nanometer line (in the case
of N0?) to the measuring phototube. The reflected beam passes
through a 578 nanometer filter to the reference phototube.
By comparing the outputs of the phototubes, the amount of
light absorbed by the SO or N02 is measured. As the absorption
of the light by the pollutants follows Beer's Law, logarithmic
amplifiers convert the phototube output signal into a linear
measurement of the specific pollutant.
The Du Pont spectrophotometric analyzer uses an air aspirator
rather than a pump to draw the sample into the system. There-
fore, a source of compressed air must be available for use
with this analyzer.
Lear Siegler, Inc. manufactures N02 and S02 spectrophotometric
flue gas analyzers which operate on a more elaborate principle.
Rather than measuring peaks in the absorption spectrum of the
3-9
-------
stack gas the instrument responds to the second derivative of
the absorption peaks. By choosing a sharp peak in the second
derivative spectrum and scanning a narrow band of it (neces-
sary to generate the second derivative) the sensitivity and
specificity of the analyzer is stated to be much improved over
that of the direct absorption spectrophotometric analyzers.
3.2.3 Fluorescence Spectrophotometers
Celesco Industries, Inc. manufactures an SO^ monitor which
operates on the principle of continuously irradiating an
aspirated sample of stack gas with short wavelength ultraviolet
light. The SO then fluoresces at a higher wavelength in
the ultraviolet. A narrow band pass filter passes the light
created by fluorescence to a photomultiplier tube which
measures its intensity. In the lower range of SO- concentra-
tion (0-500 ppm) the response is linear. Above 500 ppm the
high concentration of SO reabsorbs some of the fluorescent
light, and the response becomes logarithmic rather than linear.
Therefore, the instrument has two scales, a linear one for
0-500 ppm SO,., and a logarithmic one for 0-5000 ppm concentra-
tion of SO . The instrument contains two calibration cells
filled with sufficient SO to span the monitor. . This is
accomplished by moving a calibration cell into the optical
path in place of the sample cell. Both the high and low
scales are spanned between 50% of full scale and full scale.
As convenient as this feature is, it is not a dynamic calibra-
tion and the monitor should still be checked with external
span and zero gases at intervals closely enough spaced to
insure that it is reading the true value for SO .
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The Thermo Electron Corporation makes a pulsed fluorescent
S0? analyzer. This instrument also operates by irradiating
the stack gas in a sample cell with short wavelength ultra-
violet light and measuring the fluorescent light produced by
S02 at a longer wavelength. However, the irradiating ultra-
violet light is supplied by a flash tube which delivers the
light in short pulses. The instrument is stated to be linear
in response from 1 to 5000 ppm. Exactly how reabsorption of
the fluorescent light is avoided is not spelled out in their
literature, but a graph is provided by the manufacturer which
indicates that the instrument reading versus S0_ concentration
is linear over a range of 0 to 2500 ppm. Also the life of the
pulsating ultraviolet source is considerably longer than a
continuously operating one. The monitor must be zeroed and
spanned by calibration gases in the visual manner.
3.3 IN SITU MONITORING
3.3.1 Across the Stack Monitoring
The Environmental Data Corporation makes across the stack
monitors for NO, S0?, CO and CO . Polychromatic light is
directed across the stack to the sensor which is mounted on the
opposite side of the stack. The band of light absorbed by
the pollutant of interest is passed alternately through a
narrow band pass filter or directed straight to a reference
detector. The same detector measures the light passed alter-
nately by the filter and that sent directly to the detector
and the two signals are compared. As the unfiltered light is
affected by smoke and particulate as much as the filtered
light, the effect of the changing opacity of the stack gas is
largely cancelled out. This method avoids the problems of
sample extraction and conditioning, but as might be expected
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from its simpler optical system, adjustments must be made for
other absorbing gases. Calibration cells are automatically
inserted into the instrument at predetermined intervals to cali-
brate it. However,, this is not a dynamic calibration, and a
dynamic calibration would be very difficult to perform on
this instrument. However, a slightly less precise measurement
in the sense of actually determining the pollutant in a given
sample must be considered against the fact that the instrument
measures across the entire diameter of the stack and avoids
sampling problems.
CEA Instruments manufactures an in-stack monitor which senses
SO in a particular portion of the stack. The method of
measurement is correlation spectrophotometry which is quite
specific for SCL. It works as follows: a beam of polychro-
matic light is directed down a probe placed in the stack and
reflected back to the instrument by a mirror. A grating
generates the spectrum of the light which has passed through
the stack gas. A mask, which corresponds to the SO absorption
spectrum is oscillated across the light beam from the grating>
alternately passing the S0_ absorption spectrum and background
light. The output from a detector is measured with phase
reference to the mask position. This generates two signals,
one corresponding to SO absorption and one to background light.
As both signals are equally affected by stack opacity, the
resulting comparison of the two signals is a measurement of
the S02 in the stack. As the instrument is mounted on only
one side of the stack, it may be removed and calibrated.
Although it does perform the analysis in the stack and without
sample conditioning it monitors only a relatively small area
of the stack and therefore must be located at a spot where
the SO concentration is representative of the entire stack.
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3.3.2 Remote Sensing
Although work is in progress to use laser excitation and
Raman back scattering for remote plume sensing, no proven
instrumentation using this method is presently available.
However correlation spectroscopy, mentioned in the previous
paragraph, has been successfully used to accomplish this task.
The difference in application is that no source of light is
provided but the natural backlighting is used instead. Both
SO and NO have been monitored in stack plumes by Environmen-
tal Measurements, Inc. using this method. It works as follows:
an optical system focuses the area of interest on a mirror
grating. The grating generates the absorption spectrum of
the stack plume. An oscillating mask, cut to conform to
either the absorption spectrum of SO- or NO , alternately
passes the light of the absorption spectrum or the background
light to a detector. The electronics following the detector
are phased with the oscillating mask and generate two signals,
one correlating to the absorption spectrum and one to the
background light. The two signals are compared to obtain
the total amount of pollutant "seen" by the spectrophotometer.
The method is quite specific and can be calibrated by use of
a sample cell filled with a known concentration of the pollu-
tant being measured. The instrument, as manufactured by
Barringer Research Ltd., has the additional advantage of easily
being mounted in a mobile van. Its one disadvantage is that
it requires background light to operate.
3.3.3 Methods of Calibration and Use of Referee Methods for Checking
Performance
The extractive source pollution monitors are all calibrated
in a similar manner. Span and zero gases are connected to a
3-way T in the sample conditioning train ahead of any chilling
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or conditioning equipment. The stopcock of the T is turned to
pass the zero or span gas through the system and into the
analyzer. In most cases the zero gas is passed first and
when the analyzer has reached a steady reading it is zeroed
according to the manufacturer's instructions. A span gas
which will give approximately 80% of the full scale reading
is then passed into the T and it is continued to be passed
until the analyzer has reached a steady reading. The span of
the instruments is then adjusted so that the analyzer reads
the concentration of the pollutant in the span gas. Additional
span gases should then be passed through the system which will
cause the analyzer to read at 20%, 40% and 60% of full scale.
Any deviation in the readings from the span gas composition
should be noted, and used to plot a correction curve in
analyzing the final data. Span gas may be supplied in cylin-
ders with a certified analysis from the supplier. In the case
of low levels of pollutants, and NO in any case, permeation
tubes in appropriate span gas generation systems are prefer-
able to cylinder span gas. They are not quite as convenient,
but at low levels of pollutant, and in the case of NO-, give
more certain results if the permeation tube conditioning and
gas dilution equipment are properly operated.
In the case of the in situ monitors the calibration is more
difficult, generally requiring removal of the monitor from
the stack. Although it may require a special set up, these
monitors should be periodically calibrated with zero and
span gases as in the case of extractive monitors.
To ensure that all of the apparatus is working properly, stack
gases should occasionally be analyzed in parallel with the
instrumental monitoring using the referee methods given in the
Federal Register or the expanded EPA publications for the same
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methods. If a time limited monitoring program is being per-
formed, referee checks should be done at the start and end of
the program, and at any time inaccurate results are suspected.
If a chemistry laboratory is not available at the site to
perform the referee methods a certified outside consulting
laboratory should be called in to perform these checks.
3.4 DATA ACQUISITION
All of the continuous stack monitoring analyzers have analog electri-
cal output signals. Some come with recorders attached to record these
signals. A few even have digital output signals. If no recorder comes
with the instrument this item may be purchased separately and connected to
the analog output.
The final use of the data acquired will dictate whether a recorder tracing
is sufficient or whether the data must be recorded in a form compatible
with computer processing. If the latter is the case, an analog to digital
converter must be interfaced between the monitor and a suitable tape
recorder. The selection of this equipment is best left to the computer
program manager, as he will know best what the requirements of the equip-
ment are.
A computer program analysis of the stack monitoring data is most convenient
when a varying concentration of pollutant is to be monitored over long
periods of time. This is because intergrating many feet of chart paper
by hand is a time consuming and tedious process.
3-15
(Page 3-16 Blank)
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SECTION 4
METEOROLOGICAL INSTRUMENTS
4.0 ORIGIN
The material which follows is excerpted from the 1975 Revision of the
Air Pollution Training Institute, Course 435, Atmospheric Sampling, Chapter
XXIII. This information should prove helpful as background material for
greater understanding on the operational principles of many meteorological
instruments. The control agency inspection personnel should use this section
to become familiar with instruments which may be examined during an inspection
or review. Paragraph and figure numbers from the original document have
been retained in this section; only the page numbers have been changed.
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XXIII. METEOROLOGICAL INSTRUMENTS
A. INTRODUCTION
Measurement of atmospheric variables that affect the diffusion
and transport of air pollutants is necessary in nearly every air
pollution investigation. Suitable measurements may be available from
existing instrumentation at Weather Service city offices, airport
stations, or from universities or industries with meteorological
installations. Frequently, however, existing instrumentation does
not give detailed enough measurements; is not representative of
the area in question; or does not measure the variables desired
(such as turbulence), so additional instruments must be operated.
Of primary importance in air pollution meteorology is the
measurement of wind velocity (direction and speed) and the turbulence
of the wind. The stability of the lower layers of the atmosphere in
which the pollution diffuses is important and may be determined from
an analysis of the turbulence characteristics of the atmosphere or the
temperature lapse rate.
Of secondary importance is the measurement of humidity (which
may affect atmospheric reactions), temperature, precipitation (of
importance in washout of pollutants), and solar radiation (which
affects photochemical reactions in the atmosphere). Particularly
for research studies, it may be desirable to measure meteorological
elements affected by pollutants, such as visibility, solar radiation,
and illumination (radiation in the visible region).
B. WIND MEASUREMENTS
Surface Instrumentation for Measuring Wind Speed
Generally, wind speed sensors are broken down into the following
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categories:
Rotational Anemometers:
1. Vertical Shaft
2. Horizontal Shaft
Pressure Anemometers
1. Flat Plate Type Anemometer
2. Tube Type Anemometer
Bridled Cup Anemometer
Special Types
1. Hot Wire Anemometer
2. Sonic Anemometer
3. Bivane
4. UVW Anemometer
Pressure" anemometers, hot wire arid sonic anemometers have enjoyed
extensive use in research type operations, but they all have disadvan-
tages which have prohibited their use in operational type situations
such as air pollution surveys. The. rotational type anemometers are
the most common type of wind speed sensor in use today mainly because
they are the only types that satisfy all of the following desirable
operational features:
1. Essentially linear relationship between the sensor
output and the wind speed.
2. Calibration is unaffected by changes in the tem-
perature, pressure or humidity of the atmosphere.
3. Able to measure a wind range of wind speeds
(< 2 to 200 mph [.9 to 90 m/s] ) .
4. Long term calibration stability. The calibration
often is unchanged after 10 years continuous operation.
5. Output of the sensor is easily adapted to remote
indication.
6. Recording of the wind speed data is easily adaptable
.to either analog or digital form.
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7- Generally require extremely little maintenance.
Vertical Shaft Rotational Anemometers
A cup anemometer revolving about a vertical shaft is probably
the most frequently used anemometer. The most common of the cup
anemometers are the 3-cup types shown in Figure XXIII-1.
Traditionally, anemometers have only had to yield average
wind speeds for use in the support of aviation and weather forecast-
ing operations. Sensors often were developed with durability as the
primary requirement. These cups are about 10 cm. in diameter, with
a moment arm of about 42 cm. These anemometers, due to their large
mass, have a relatively high starting speed (that wind speed at which
the cups first begin to rotate or reach the manufacturers accuracy
specifications) of about 3 mph (1.4 m/sec). This factor of high mass
combined with a long moment arm will also produce a high moment of
inertia which tends to cause the cups to indicate erroneous wind
speeds under gusty conditions. Not only will the instantaneous
readings be in error, but because the cups accelerate faster than
they decelerate, the mean speed indicated may be slightly higher than
the true speed.
With the advent of environmental concern, an anemometer was
needed that would measure light winds, which are of great importance in
air pollution meteorology. Also, to support turbulence and diffusion
studies, an anemometer was needed that would approach giving an instan-
taneous response to wind speed fluctuations. Lighter weight anemometers
were developed for such purposes. To provide accuracy at low speeds
and greater sensitivity, these small 3-cup anemometers are lightweight
in construction (plastic or very thin aluminum) and employ a relatively
short moment arm. In addition, friction has been reduced by utilizing
miniature ball bearings and special type transmitters. The cups are
generally 5 cm. in diameter and have a moment arm of about 7 cm. The
result of these design considerations is more accurate instantaneous
and average windspeeds.
The cup xvheel has been redesigned in an attempt at further
4-4
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Figure XXIII-1: 3-CUP ANEMOMETRIC (COURTESY CLIMET INSTRUMENTS)
4-5
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reducing the starting speed: by using six staggered cups, a greater
surface area is exposed to the wind. This factor decreases the
starting threshold from .75 mph (.35 m/s) for the standard 3-cup
anemometer to .4 - .5 mph (.2 - .25 m/s). This design also pro-
duces a more uniform torque around the entire shaft revolution.
Horizontal Shaft Rotational Anemometers
The second most commonly used wind speed measuring system is
one that has a propeller on the end of a horizontal shaft that is
oriented into the wind by a vane on the opposite end of the shaft.
A propeller anemometer is shown in Figure XXIII-2. The propeller
is usually helicoidal in design, with the rate of rotation of the
propeller being linearly proportional to the wind speed. As with
the cup anemometers, the propeller anemometers generally fall into two
design categories: 1) those designed with durability as a prime
consideration and 2) those designed with sensitivity as a prime
consideration.
The more sensitive propeller anemometers utilize lightweight
aluminum or plastic as blade material, and generally employ either 2
or 4 blades. The 2-bladed propellers have starting speeds of about
.4 - .7 mph (.2 - .35 m/s), while the 4-bladed propellers have a
threshold of about .3 - .5 mph (.15 - .25 m/s).
The more durable propeller anemometers use heavy gauge plastic
or steel in the blade construction. Because of the relatively
heavy mass, they have higher starting speeds of about 2.5-3 mph
(1.2 - 1.5 m/s).
The sensitivity argument developed earlier for the cup anemome-
ters also applies to propeller anemometers. However, because of the
helicoidal design of the blades, the number of blades has no effect
on the torque uniformity. The design produces a uniform torque
independent of the number of propeller blades.
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Figure XXIII-2: PROPELLER ANEMOMETER (COURTESY CLIMET INSTRUMENTS)
4-7
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Special Types of Anemometers
The propeller bivane anemometer is capable of measuring the
magnitude of the wind vector and will be discussed more fully in the
wind direction sensor portion of this section.
The UVW anemometer is another sensor configuration that yields
the wind vector and its fluctuations is the UVW anemometer. Figure
XXIII-3 shows one type manufactured by Climet Instruments. In this
sensor configuration, a propeller anemometer is mounted in each
principal axis (thus the name UVW), and each yields the component
wind vector in that axial direction. This anemometer has found
limited operational use because of the sophisticated data reduction
that is necessary to convert from an output of three wind speeds to
a vector magnitude and direction. The UVW anemometer has, however,
enjoyed easy application to those situations where the three com-
ponent vectors are the only desired output, or where data reduction
is accomplished through the use of a computer. As with all sensors
of the propeller type, serious error is introduced during periods
of heavy precipitation, and with this particular propeller configura-
tion there is some mutual interference error with certain wind direc-
tions.
Wind Speed Measuring Transducers
The most common aerodynamic sensor for the measurement of wind
speed is the cup or propeller. The wind speed measuring transducer
must convert this cup or propeller rotation to an energy form that is
easily transmittable. The energy form is usually electric and the trans-
ducer is commonly one of the four types discussed subsequently.
D.C. Generator
Small, permanent field D.C. generators are used that have an
output which is linearly proportional to the rate of turning of the
cup or propeller and, hence, is linearly proportional to the wind
speed. The output from this transducer can be recorded directly on
any D.C. galvanometer recorder. The main disadvantage of D.C.
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Figure XXIII-3: UVW Anemometer (Courtesy Climet Instruments Co.)
-------
generators is the relatively high starting or threshold-speeds. The
brush and bearing friction combine to produce a lower limit to the
threshold speed of about 1 mph (.5 m/s) on the most sensitive systems.
The brushes on these generators usually need servicing only about
once a year under continuous use. On some of the more sensitive
I
sensors the unit is sealed and it is recommended that the unit be sent
to the factory for servicing or replaced completely.
0 A.C. Generator
In an attempt to lower the threshold speed by eliminating brush
friction, some manufacturers are using A.C. generators instead of B.C.
generators. A.C. generators reduce the friction considerably and
eliminate brush and commutator maintenance. A.C. generators are
available with either two, four, six, or eight-pole permanent magnet
rotors. The larger the number of poles, the more pulses are available
per shaft revolution, producing a smoother record.
The largest disadvantage of the A.C. generator is associated with
the number of pulses per shaft revolution. These pulses must be
rectified by a modifying transducer (rectifier) in order to have a
suitable energy form for recording.. Low wind speeds generate a low
frequency of A.C. pulses and normal-rectifiers do not function properly
with a low frequency input. Thus, spurious oscillations may be produced
at low wind speeds. Therefore, to obtain wind speeds below about
2 m/sec (4 mph) some sort of electronic correction is needed. This
disadvantage defeats the purpose of reducing the friction and has
therefore resulted in a minimal use of this type of transducer.
Interrupted Light Beam
Further reduction in friction with accompanying lower threshold
speed and quicker response can be accomplished with the use of an
interrupted light beam (light chopper) transducer. This transducer
employs either a slotted shaft, a slotted disc (Figure XXIII-4), a
light source and a photocell, or photo-diode. The cup or propeller
rotates the slotted shaft or disc and a pulse is created each time a
slot allows light from the source on one side of the shaft or disc to
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fall on the photocell on the other side of the shaft or disc. The
larger the number of slots in the shaft or disc, the smoother will
be the output, especially at low wind speeds. The output from the
transducer is handled in the same manner as the output from the A.C.
generator. The large number of slots (about 100) prevent spurious
oscillations in the output at low wind speeds.
i CUP ANEMOMETER
PRECISION BEARINGS
Figure XXIII-4
(Courtesy Climet
Instruments Co.)
Mechanical - contact type
All of the measuring transducers mentioned so far produce an analog
signal. There are circumstances where the desired output might be total
miles of wind passage instead of a time plot of wind speed. Under these
circumstances, a mechanical-contact transducer is used. In this type of
transducer, the anemometer shaft is connected through one or more gears
to a cam or similar device that opens or closes a contact after the passage
of a pre-determined amount of air. This contact closure can operate a
readout device such as an event marker pen on a recorder. Recorders
can be furnished with circuitry to provide a pen actuation for each
10, 100, or 1000 contact closures in the transducer. If the average
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wind speed is desired instead of length of wind passage, the number
of contact closures are determined for a given time increment and,
knowing the miles or meters of wind passage for each contact closure,
the average wind speed over the given time increment is easily deter-
mined.
Wind Direction Measuring Instruments
Flat Plate Vane
Typical flat plate vanes are shown in Figure XXIII-5. The
term flat plate refers to the tail shape which is simply a flat
plate. The flat plate can take on a number of different shapes and
be made out of a number of different materials. As with wind speed
sensors, the material used in constructing the wind vane will
generally determine the proper use of the vane. Vanes made out of
heavy gauge metal or plastic should be used only for obtaining
average wind direction. The large mass creates a high moment of
inertia which will give, under certain conditions, a much higher
indication of wind fluctuations than actually exists. The light-
weight sensitive vanes have tails 'made out of thin gauge aluminum
or plastic or molded expanded polystyrene. The counterweightss are
also close to the center of rotation. This design creates a highly
sensitive vane that can be suitably used for turbulence or other
fine analyses of the wind trace.
Splayed Vane
In this type of vane, two flat plates are joined at a small
angle (usually about 15 ) at one end of the horizontal shaft. This
design came about through experimentation that showed that the splayed
vane followed small changes in wind direction better than the flat
plate. However, the increased mass incurred by two flat plates
makes this type of vane unsuitable for anything but the measurement
of average wind direction. The splayed vane has, mainly because of
its durability and reliability, found widespread use in its
role as the main wind direction sensor for the National Weather
Service. Therefore, it should be noted that wind direction data
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Figure XXIII-5: WIND DIRECTION SENSOR (COURTESY CLIMET INSTRUMENTS)
4-13
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obtained from a National Weather Service should be used only as an
indication of average wind direction.
Aerodynamic Shaped Vane
The aerodynamic shaped vane has an airfoil cross section. This
type of vane has been shown to produce up to 15% more torque for
certain ranges of attack angles than a flat plate vane of similar
physical dimensions. This type of design, as with the splayed vane,
incorporates more mass than the flat plate vane and therefore pro-
duces a higher moment of inertia, yielding a poor dynamic performance.
An aerodynamic wind vane that has found wide-spread use in air
pollution studies the "Aerovane". It should be remembered that its
dynamic performance is inferior to the sensitive vanes of Figure
XXIII-5, and the use of the data gathered by the "Aerovane" should
reflect this fact.
Bi-directional Vanes (Bivanes)
This type of instrument is designed to rotate around a vertical
axis to measure the azimuth angle of the wind, as does a conventional
wind vane. It also can move in the vertical to measure the elevation
angle of the wind. Because the vertical motions of the atmosphere.
are frequently of a different character than the horizontal motions
(anisotropic turbulence), measurement of both the horizontal and ver-
tical motions are desirable. This is particularly true under stable
conditions when the vertical motion is almost absent, but horizontal
changes in wind direction may be appreciable. Micropotentiometers
are usually used to produce an analog record of both angles. The
total wind speed can be measured by replacing the counterweight with
a propeller anemometer. Figure XXIII-6 shows a typical anemometer
bivane.
Wind Direction Measuring Transducers
The measurement of wind direction consists of converting the
angular position of the wind vane to an energy form that can be
transmitted easily. Wind direction systems usually employ one of
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Figure XXIII-6: AXIOMETER WIND TRANSMITTER - BIVANE
(COURTESY CLIMET INSTRUMENTS)
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three types of measuring transducers: a potentiometer system,
a synchro-motor system or a commutator system.
Potentiometer System
The most common and inexpensive way of converting the angular
position of the vane to an electrical signal is through the use of a
potentiometer system. In this system the shaft of the vane is attached
to the wiper arm of the potentiometer. The swinging vane therefore pro-
duces a continuously varying voltage that can be recorded on a re-
cording voltmeter or dial indicator. With proper calibration, the
recorded voltage gives a direct reading of the angular position of the
vane.
The biggest drawback to this system is the unavoidable dis-
continuity in the potentiometer. If the wind direction is oscilla-
ting about a direction corresponding to this gap (usually north) , the
voltage output will oscillate between the maximum and minimum value
producing what is commonly called "chart painting." With the recorder
pen swinging from one end of the chart to the other, the record pro-
duced is, at best, very confusing. There are some types of recorder
pen movements available that circumvent this problem. Double contact
potentiometers with dual pen recorders produce a trace along each
edge of-the chart when the wind direction corresponds to the gap.
Figure XXIII-6 illustrates a chart record of this type. In newer
recorders, there is available electronic circuitry and a 540 chart
that can keep the pen trace in the central portion of the chart.
Figure XXIII-7 illustrates a chart record of this type.
Wire, potentiometers present a problem of excessive wear pro-
duced as the contact moves along the wires. The life expectancy
of wire-wound potentiometers is only about a year under conditions of
continuous operation. Recent advances in this area have produced a
conductive plastic potentiometer. The life expectancy of these poten-
tiometers is about 50 x 10 oscillations, or three to five years,
under continuous operation. The linearity of these devices is about
.5%.
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Figure XXIII-7:
Dual Pen Recorder
Chart
Figure XXIII-8:
540ฐ Recorder
Chart
4-17
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The use of micro-potentiometers produces the lowest moment
of inertia of any of the direction transducers available today. This
fact has led to their widespread use in the sensitive wind vanes
that are noted for their good dynamic performance.
9 Synchro-motor Systems
Commonly known as "Autosyn", "Selsyn" or "Synchrotie" systems,
this transducer system consists of two synchronous motors wired so that
any movement by the shaft of the transmitter will be duplicated by the
shaft of the receiver motor, usually to an accuracy of about 2 ,
provided the lead resistance is kept to a maximum of 20 ohms. The
vane shaft is coupled to the shaft of the transmitter motor and the
shaft of the receiver motor is coupled to a recorder pen or some other
read-out indicator. Therefore, any vane movement is duplicated by a
movement of the dial needle, recorder pen, etc., and with proper cali-
bration and alignment, a direct indication of wind direction is
obtained. There is no discontinuity in the movement "as with the
potentiometer. This transducer system is usually coupled with a
540 chart recorder system or a dial indicator to produce an analog
trace of wind direction. The system also lends itself readily to a
dial indicator display. The only disadvantage of this transducer system
is the relatively large moment of inertia of the motor assembly. This
produces a poorer dynamic performance than the micro-potentiometer system
and limits their use to the more rugged vane types such as the
"Aerovane."
Commutator System
The wind direction transducers discussed so far produce an analog
signal that can be converted to an analog chart trace. The commutator
transducer system produces contact closures which can be used to activate
lights, event marker pens, etc. In this system, the vane shaft is coupled
to a unit that has two brush-type contacts spaced 22^ degrees apart.
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These brushes make contact with one or two of the eight conducting
sectors that are spaced 45 apart and correspond to 45 of wind
direction. When both brushes contact the same sector, the direction
indicated is one of the .eight compass points, eg., N, NE, E. > If
the brushes are contacting two of the sectors, the indicated direc-
tion corresponds to an intermediate direction, such as NNE, ENE, ESE,
etc. Therefore, direction indication to 16 points can be obtained
with this system. The friction inherent in the commutator trans-
ducer as well as the crude method of display make this transducer
most applicable to operations involving only the acquisition of
average wind direction.
Airborne Sensors
Fixed location wind velocity sensors measure the wind at a
fixed height as it varies with time. Most airborne sensors are used
to average wind velocity through a given depth of the atmosphere at
a particular time.
Pilot Balloon (pibal)
This method of measuring wind' velocity uses a gas-filled free
balloon which is tracked visually through a theodolite. The theodo-
lite is an optical system used to measure the azimuth and elevation
of the balloon. When only one theodolite is used, the balloon is
inflated to have a given amount of free lift. The elevation and
azimuth angles are used with the assumed ascent rate to compute wind
directions and speeds aloft. By using two theodolites to track the
pibal, the ascent rate of the balloon is not assumed, but calculated
from the elevation and azimuth angles of the two theodolite observa-
tions taken simultaneously. The two theodolites are set a known dis-
tance apart (the baseline). Two types of pilot balloons frequently
used reach 3000 ft. within five minutes and eight minutes, respectively,
after release. If detailed structure of winds with height is to
be determined, readings of azimuth and elevation angle must be read
every 15 or 30 seconds.
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Rawinsonde
This method of measuring wind velocity aloft also uses a gas-
filled free balloon, but is is tracked either by radio direction
finding apparatus, or by radar. The former method is the most
frequently used in the U.S. The radio transmitter carried by the
free ballpen is usually used to transmit pressure, temperature and
humidity information to the ground (radiosonde). The radio direction
finding equipment determines the elevation angles and azimuth angles
of the transmitter. The height is determined by evaluation of the
temperature pressure sounding. Using radar the slant range is
available for determining height. Soundings taken with this type
of equipment are made on a routine basis for supporting forecasting
and aviation activities. The ascension rate of these balloons is on
the order of 1000 feet/minute, so they do not yield as detailed
information on winds in the lowest part of the atmosphere as is desired
for many air pollution meteorological purposes.
Rocket Smoke Plumes
A system using a cold propel!ant, recoverable rocket to emit a
vertical smoke trail to an altitude of 1200 feet has been developed
by Gill, Bierly, and Kerawalla. This smoke trail is photographed
simultaneously at short time intervals by two cameras 2000 feet from
the launch site and at right angles to each other. The difference in
position of the smoke trail from two successive photographs is a mea-
sure of one component (north-south for example) of the wind and can
be determined at any number of heights from gound level to 1200 feet.
Another system has been reported by Cooke (2).
Constant Level Balloons
Unlike the previous airborne sensors for wind velocity which
obtain average measurements through a vertical layer, constant level
balloons are used to determine the trajectory or path of an air parcel
during a given time interval. In order to maintain a constant altitude
more accurately to fly along a constant air density surface the
balloon must maintain a constant volume. A tetrahedron shaped balloon
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(tetroon) of mylar has been used for this purpose, having been
tracked visually and by radar (1).
C. TEMPERATURE LAPSE RATE
The vertical structure of temperature gives an indication of
the stability and turbulence of the atmosphere.
Temperature Difference Measurements
One method of estimating the vertical structure of temperature
is by measuring the difference in temperature between sensors mounted
at different heights. This, of course, gives an average condition
between any two particular sensors.
Heights of Sensors
Because of the pronounced influence of the earth's surface on
the atmosphere's temperature, it may be desirable to measure tempera-
ture difference at closer intervals near the ground than at higher
levels. For example, a 300 foot tower might have sensors at 5 feet
25 feet, 50 feet, 100 feet, 200 feet, and 300 feet. The height
differences at the upper levels should be about equal so that the
height of inversions may be determined. Radio and television towers
are good supports for temperature difference sensors (as well as wind
sensors) and stations usually are willing to allow sensors to be
mounted upon their towers. Of course, sensors must be kept below the
level of the transmitting antenna.
Sensors
Resistance thermometers of copper or nickel may be used for
temperature difference systems. Thermocouples of copper-constantan
or iron-constantan also make reliable sensors. Resistance thermom-
eters and thermocouples do not have to be frequently calibrated and
may be expected to provide good service for 10 to 20 years if property
installed. Thermistors are not generally recommended because they
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may be quite variable from unit to unit and they may require re-
calibration more frequently than the other two types of sensors.
Rapid response is usually not desired in measuring temperature
differences. Rather, averages on the order of 5 minutes are desired.
If the sensors are 1/2 to 5/8 inch in diameter, they will respond
slowly enough to give an average temperature.
Shielding and Ventilating
Guidelines for the exposure of temperature sensors can be best
found in references (3), (4), (7), and (10).
Recorders
Generally multiple point (10 or 20 points) recorders are
used for recording temperature differences. Thus, one recorder may
be used for the entire system. The recorder is connected to one sensor
for about 30 seconds, prints and then switches to another level. If
a six minute cycle is used (print for each level every 6 minutes) there
will be 10 readings every hour and an hourly average may easily be
obtained by adding the 10 readings and shifting the decimal point one
place. The sensors are usually wired so that the temperature differen-
ces are obtained directly rather than determining the temperature at
each level.
Balloon-borne Sensors
Temperature sensors may be lifted by either free or captive
balloons. By this method, temperature, not temperature difference,
is measured.
Radiosonde
The method of radiosonde (radio-soundings) observations
is used routinely for temperature, pressure and humidity soundings
of the upper air. A free balloon carries the sensors and a radio
transmitter aloft. Cycling from sensor to sensor is by means of an
aneroid barometer and consequently is a function of pressure.
Observations are normally made twice daily at 0000 GCT and 1200 GCT
at approximately 70 stations in the contiguous U.S. The ascent rate
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of the balloon is about 1000 ft/minute. Generally only four to six
temperature readings are recorded within the lower 3000 feet so the
vertical temperature information is not too detailed. It is still of
considerable use when more detailed information is not available.
T-Sonde
This system consists of a temperature sensor and radio trans-
mitter which is carried aloft by a free rising balloon. The main
difference between this system and the radiosonde system is that only
temperature is measured. Ten to twelVe measurements are taken within
the lower 3000 feet of the atmosphere, thus giving more detailed
structure of temperature with height.
Tethered Kite Balloon
Using a captive balloon system to make vertical temperature
measurements has the advantages of complete recovery of all components
of the system, and as detailed a temperature sounding as is desired
may be made by control of the level of the sensor. A balloon having
fins is much easier to control and gives greater lift in slight winds
than a sperical balloon. Most kite' balloons can be used in winds less
than 15 knots. For air pollution meteorology purposes, the light wind
periods are of greatest interest anyway. Because of hazards to air-
craft, prior permission from the FAA is required for flights exceeding
500 feet above ground. For additional precautions when using captive
balloons, references such as Doebelin (3), Hewson (4), and Middleton
and Spilhaus (7) are suggested.
Several methods of relaying the observations to the ground have
been used. Using a wiresonde, a resistance thermometer is carried
aloft by a kite balloon whose mooring cable contains wires connecting
the sensor with a wheatstone bridge on the ground which is used to
measure the resistance. Another system uses a modified radiosonde
transmitter to measure temperature and humidity. The signal is trans-
mitted to the ground receiver and recording equipment by the same
method used in the radiosonde. Cycling from one sensor to another j
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by a battery driven timing device. The temperature sensor is shielded
from the sun by the styrofoam plastic and is aspirated by a small-
motor driven fan. The mooring of this system is by nylon cable marked
at intervals to indicate the height of the sensor.
Aircraft Borne Sensors
In some cases, light aircraft or helicopters have been used for
obtaining temperature lapse rate measurements. Although there are
complete systems commercially available for this method of temperature
lapse rate measurement, one can use standard temperature sensors,
thermisters, resistance thermometers, etc., and recorders as long as the
exposure guidelines are carefully followed (3, 4, 7).
D. THE MEASUREMENT OF SECONDARY METEOROLOGICAL PARAMETERS
Precipitation
Because large particles and water soluble gases may be removed
from the atmosphere by falling precipitation, measurements of this
element may be needed. Chemical or radioactive analysis of rain water
may also be desired.
Standard Rain Gauge
The standard rain gauge consists of a metal funnel 8 inches in
diameter, a measuring tube having 1/10 the cross-sectional area of
the funnel, and a large container of 8 inches diameter. Normally
precipitation is funneled into the measuring tube. The depth of water
in the tube is measured using a dip stick having a special scale
(because of the reduction in area). Measurements with this instrument,
since they are made manually, give only accumulation since the last
measurement.
Recording Rain Gauge
The recording or weighing bucket rain gauge does give detailed
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time resolution of occurrence, and amount of precipitation, as a
strip chart, with one revolution per day, is used. The gauge con-
sists of a bucket, to hold the precipitation, on a scale, which weighs
the precipitation and moves the pen arm, recording the total accumu-
lation on the chart which is calibrated in inches.
Tipping Bucket Rain Gauge
This precipitation gauge has a bucket with two compartments
beneath the collecting funnel. When one side of the bucket collects
a given amount (usually 0.01 inch) of precipitation, the bucket tips
and empties the precipitation, collecting the next portion in the other
side. The bucket movements are recorded on a chart. The number of
bucket movements and the time they occur indicate the rainfall amount
and rate. This type instrument is not suitable for measuring snow.
Precipitation Collector
For research purposes, it is desirable to analyze rainfall as
to its chemical and radioactive constituents. Since it is desirable
to include only precipitation samples, and not material that may
fall into the collector during dry periods, a collector which opens
only during periods of precipitation has been developed. The sensor has
two sets of adjacent wires and a raindrop falling between the wires
completes an electrical circuit which removes the cover from a poly-
ethylene container. A small heat source dries the sensor so that the
circuit will be broken when precipitation ceases and also so that
dew will not form and open the collector.
Humidity
Because of its influence upon certain chemical reactions in the
atmosphere and its influence upon visibility, it may be desirable to
measure humidity in connection with an air pollution investigation.
Also, some air pollutants affect receptors differently with different
humidities, so measurement may be of importance in this respect.
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6 Hygrothermograph
This instrument measures both temperature and humidity, activa-
ting pen arms to give a continuous record of each element upon a strip
chart. The chart generally can be used for seven days. The humidity
sensor generally used is human hair which lengthen as relative humidi-
ty increases and shorten with humidity decreases. Temperature measure-
ments are usually made with a bourdon tube, a curved metal tube contain-
ing an organic liquid. The system changes curvature with changes in
temperature, activating the pen arm.
Psychrometers
Humidity measurement by a psychrometer involves obtaining a dry
bulb temperature and a wet bulb temperature from a matched set of
thermometers. One thermometer bulb (wet bulb) is covered with a muslin
wick moistened with distilled water. There must be enough air motion
to cause cooling of the wet bulb due to evaporation of the water on the
wick. A motor driven fan may be used to draw air at a steady rate
past the moistened wick while a reading is taken. A sling psychrometer
has both thermometers mounted on a frame which is whirled through the
air to cause cooling by evaporation. Relative humidity is determined
from the dry and wet bulb readings through the use "of tables. Contin-
uous measurements of humidity are not obtained using psychrometers.
Radiation
The influence of the sun's radiation upon the turbulence of the
atmosphere and upon certain photochemical reactions is sufficient to
make measurements of radiation of importance. In addition, radiation
may be reduced due to particulate pollution in the atmosphere.
Particularly for research purposes, it may be desirable to measure this
effect by comparisons between urban and non-urban stations similarly
instrumented.
ฎ Total Radiation
The direct radiation from the sun plus the diffuse radiation from
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the sky may be measured by pyranometers. These instruments are
mounted so that the sensor is horizontal and can receive the radia-
tion throughout the hemisphere defined by the horizon.
0 Direct Solar Radiation
The direct solar radiation may be measured continuously by using
a pyrheliometer mounted upon an equatorial mount to keep it pointed
toward the sun. By using filters, different spectral regions of
radiation may be determined.
Net Radiation
The difference between the total incoming (solar plus sky) radia-
tion and the outgoing terrestial radiation may be useful in determining
the stability, and hence, the turbulent character, of the lowest por-
tion of the atmosphere.
Visibility
Visibility, in addition to being affected by precipitation, is
affected by humidity and air pollution. Frequently, visibility is
estimated by human observer. An instrument to measure visibility,
called a transmissometer, measures the transmission of light over a
fixed baseline, usually on the order of 500 to 750 feet. An intense
light source from the projector is focused on a photocell in the
detector. The amount of light reaching the photocell over the con-
stant baseline distance is assumed to be proportional to visibility.
The transmissometer is restricted to estimating visibility in one di-
rection only.
A transmissometer is also limited in that the light trans-
mission it detects is affected mainly by liquid droplets in the air.
It does not detect, to any great efficiency, the particulate matter in
the atmosphere. A relatively new instrument, called a nephelometer,
has been developed that will indicate visibility as it is affected by
particulate matter in the atmosphere.
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REFERENCES
1. Angell, J.K. and Pack, D.H., "Analysis of Some Preliminary Low-
Level Constant Level Balloon (Tetroon)
Flights." Mon. Wea. Rev. 88, 235 (1960).
2. Cooke, T.H., "A Smoke-Trail Technique for Measuring Wind." Quart.
J. Roy. Meteorol. Soc. 88, 83 (1962).
3. Doebelin, E.G., Measurement Systems: Application and Design.
McGraw-Hill Co., New York.
4. Hewson, E.W., "Meteorological Measurements." Air Pollution.
Vol. II New York, Academic Press.
5. Hewson, E.W., and Gill, G.C., Report submitted to the Trail Smelter
Arbitral Tribunal by R.S. Dean and R.E. Swain,
U.S. Bur. Mines Bull. 453, 1944.
6. Lockhart, T.J., "Bivanes and Direct Turbulence Sensors. "Meteoro-
logy Research Inc. MRI 170 Pa 928, June,
1970.
7. Middleton, W.E.K. and Spilhaus, A.F., Meteorological Instruments.
Toronto, University of Toronto Press, 1953.
8. Slade, D.H., Editor, "Meteorology and Atomic Energy-1968". U.S.
AEC, Division of Technical Information.
9. Stein, P.K., "Classification Systems for Transducers and Measuring
Systems." Symposium on Environmental Measure-
ments, U.S. Dept. HEW, July, 1964.
10. Stern, A.C., Editor, Air Pollution. Second Edition Vol. II
New York, Academic Press. 1968.
U.S. GOVERNMENT PRINTING OFFICE: 1975-210-810:63
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing!
1. REPORT NO.
EPA-340/1-75-008
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Guidelines for Enforcement and Surveillance of
Supplementary Control Systems
S. REPORT DATE
September 1975
6. PERFORMING ORGANIZATION CODE
7.AUTHORIS) R.J. Bryan, P.C. Kochis, J.W. Boyd, M.L.
McQueary and R.L. Norton
8. PERFORMING ORGANIZATION REPORT NO
I. PERFORMING ORGANIZATION NAME AND ADDRESS
Pacific Environmental Services, Inc.
1930 14th Street
Santa Monica, California 90404
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA Contract No.
68-02-1390
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Protection Agency
Regional Program Section
Division'of Stationary Source Enforcement (EG 341)
Washington. D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Guidelines for the enforcement and surveillance of Supplementary Control Systems (SCS)
are presented in two Volumes. 35 References. For Volume I these include:
1. Description of SCS elements and discussion of SCS violations
2. Types of inspections and review procedures used for surveillance
and enforcement
3. Inspection and calibration procedures (together with sample check-
lists and forms) for ambient and emission monitors and meteorological
instruments.
Volume II contains detailed background information on inspection and calibration of
SO- ambient and emission monitors and meteorological instruments.
This document is not a research report. It is designed for use by operating
personnel.
This work was submitted in partial fulfillment of Contract 68-02-1390 by Pacific
Environmental Services, Inc. under the sponsorship of the Environmental Protection
Agency. Work was completed as of September 1975.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Supplementary Control System
Air Pollution Control
Intermittent Control System
14B
I. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
155
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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