Guidelines for CEMS Performance Specifications

and Quality Assurance Requirements

for Municipal Waste Combustion Facilities

September 1990

U.S. EPA Contract No. 68D90055

Work Assignments 15 and 37

Prepared by:

James W. Peeler

CEM/Engineering Division

Entropy Environmentalists, Inc.

Research Triangle Park, North Carolina 27709

Prepared for:

Nancy Seidman

Northeast States for Coordinated Air Use Management

By agreement with:

Emission Measurement Branch

Technical Support Division

U.S. Environmental Protection Agency

Research Triangle Park, North Carolina 27711
ACKNOWLEDGEMENTS

This guideline document is based on discussions of a workgroup

organized by the Northeast States for Coordinated Air Use

Management (NESCAUM). The workgroup was created to provide

guidance to state and local agencies which use or plan to use

continuous emission monitoring systems (CEMS) to determine

compliance at municipal waste combustion (MWC) facilities. The

guidelines are intended to promote consistency in designing and

operating CEMS and reporting monitoring data. The document

reflects the recommendations of state and federal agency staff. In

addition, a draft of these guidelines was distributed to other

agencies, CEM equipment vendors, and MWC owners and operators.

Their comments and suggestions were reviewed and discussed by the

workgroup and appropriate changes were made to the guidelines.

This project was funded by the NESCAUM states, the US

Environmental Protection Agency Regional Offices in Boston, New

York, and Philadelphia, the Stationary Source Compliance and

Technical Support Divisions of the US Environmental Protection

Agency's Office of Air Quality Planning and Standards, and the US

Environmental Protection Agency's Office of Research and

Development in the Atmospheric Research and Exposure Assessment

Laboratory. We thank all of the people who helped fund this

project.

The workgroup was organized and managed by Nancy L. Seidman,

Special Projects Director of NESCAUM. The workgroup members were

drawn from state and federal agencies. The members of the

workgroup are listed below.

California Air Resources Board - Robert Fletcher, Peter

Ouchida

Connecticut Bureau of Air Management - Carl Dodge, Mark Peak,

Joe Ulevicus

Maine Bureau of Air Quality Control - Jane Longfellow, Scott

Mason

Massachusetts Division of Air Quality Control - Ed Braczyk,

Robert Quevillon, William Sullivan

New Hampshire Air Resources Division - Andrew Bodnarik, Jack

Glenn

New Jersey Division of Environmental Quality - Ed Choromanski,

Don Patterson

New York Division of Air Resources - Frank Buckman, Robert

Kerr, Tim Ross

NESCAUM - Nancy Seidman

Ohio Division of Air Pollution Control - Tammy Hilkens

Pennsylvania Bureau of Air Quality Control - Joe Nazzaro

Vermont Air Pollution Control Division - Brian Fitzgerald

U.S. Environmental Protection Agency

Region I, Boston - Tom Elter, Mary Ellen Stanton

Region II, New York - Ann Zownir
Region II, Philadelphia - Robert Vollaro

Office of Air Quality Planning and Standards, Stationary Source

Compliance Division - Louis Paley

Office of Air Quality Planning and Standards, Technical Support

Division - Terry Harrison, Gil Wood

Office of Research and Development, Atmospheric Research and the

Exposure Assessment Laboratory - Tom Logan

James W. Peeler and George W. Walsh of Entropy

Environmentalists, Inc. participated in workgroup meetings, helped

direct the efforts of the workgroup, and prepared this document.

We gratefully acknowledge the time invested by the workgroup.

Their assistance and expertise made this project possible.
CONTENTS

Page

Section 1 SUMMARY 1

Section 2 PERFORMANCE SPECIFICATIONS FOR SO2 AND NOx CEMS 7

AT MUNICIPAL WASTE COMBUSTION FACILITIES

Section 3 PERFORMANCE SPECIFICATIONS FOR CO CEMS 15

AT MUNICIPAL WASTE COMBUSTION FACILITIES

Section 4 PERFORMANCE SPECIFICATIONS FOR HCl CEMS 21

AT MUNICIPAL WASTE COMBUSTION FACILITIES

Section 5 QUALITY ASSURANCE REQUIREMENTS FOR SO2, NOx, 25

CO, AND HCl CEMS

Section 6 EQUIPMENT AND PERFORMANCE SPECIFICATIONS FOR 33

OPACITY CEMS AT MUNICIPAL WASTE COMBUSTION FACILITIES

Section 7 QUALITY ASSURANCE REQUIREMENTS FOR OPACITY CEMS 37

Appendix Comparison of Accuracy Specifications
SECTION 1 -- SUMMARY

This guideline document is based on discussions of a workgroup

organized by the Northeast States for Coordinated Air Use

Management (NESCAUM). The workgroup was created to provide

guidance to state and local agencies which use or plan to use

continuous emission monitoring systems (CEMS) to determine

compliance at municipal waste combustion (MWC) facilities. The

guidelines are intended to promote consistency in designing and

operating CEMS and reporting monitoring data. The document

reflects the recommendations of state and federal agency staff. In

addition, a draft of these guidelines was distributed to other

agencies, CEM equipment vendors, and MWC owners and operators.

Their comments and suggestions were reviewed and discussed by the

workgroup and appropriate changes were made to the guidelines.

The NESCAUM recommendations reflect a consensus of the

workgroup participants arrived at through discussions during

several meetings. The resulting recommendations reflect the

collective experience, opinions, and judgement of the workgroup

participants from the regulatory agency perspective. The scope of

this project did not include the acquisition or analysis of data or

other information to serve as the basis for specific requirements

or recommendations. 

The NESCAUM workgroup recommends that states adopt regulations

which require the use of CEMS to determine compliance with emission

standards on a continuous basis at MWC facilities. The regulations

should:

· Establish initial certification procedures and requirements for

CEMS

· Define quality assurance (QA) procedures and criteria for the

ongoing determination of the acceptability of the CEMS and the

monitoring data

· Specify minimum data capture requirements

The CEMS requirements in 40 CFR 60, including 60.13

"Monitoring requirements", Appendix B - Performance Specifications,

and Appendix F - Quality Assurance Procedures are recommended as

a working base for state regulations. The federal requirements,

however, are recognized as the minimum needed to ensure reliable

CEMS performance and acceptable emissions data. The federal

regulations have not been recently revised to keep up with the

evolution of CEM technology. Recommendations are included here to

address problems encountered in actual practice which are not

adequately resolved by the existing federal regulations. The

recommendations are specifically designed for CEMS programs at MWC

facilities and they attempt to address technical issues that may be

encountered in the implementation of monitoring programs subject to

a wide variety of state regulations. It is hoped that these

recommendations will facilitate a more consistent approach in state
CEMS programs and requirements. 

State requirements for emission standards, percent removal

requirements, averaging times, and reporting may differ

substantially from the EPA New Source Performance Standards

currently being developed. Significant differences among the

various state regulations are also likely. Therefore, the NESCAUM

workgroup recommendations for performance specifications and

quality assurance procedures are presented in general terms rather

than in specific regulatory language. States desiring to adopt

these recommendations will need to make appropriate modifications

to them so that they are compatible with the applicable emission

standards and other existing regulations. Specific language for

requirements based on the modified recommendations and the

referenced federal regulations will also need to be developed by

each state agency.

The following sections of this document present detailed

recommendations for performance specifications and quality

assurance requirements for gas and opacity CEMS. Many of the

specifications are expressed in terms of "percent of span" since

the actual measurement range of the instrumentation should be

specified by the state agency to be compatible with the applicable

regulations and enforcement policies. In specifying the span

value, the agency should consider trade-offs between an expanded

measurement range and more accurate data at typical emission levels

or at the level of the emission standard. Some factors to consider

in specifying the span value include: the applicable emission

standard or percent removal requirement, the averaging time for the

standard, the inherent variability of uncontrolled and controlled

emissions during normal operation and during malfunctions of the

facility, and the actions to be taken by the agency and the source

owner or operator if emissions exceed the measurement range of the

CEMS. 

The recommendations presented in this document were developed

for MWC facilities. Many of these recommendations could also be

applied to other sources; however, no attempt was made in this

project to identify or address the specific technical and

regulatory issues associated with CEMS programs at other source

categories. These issues include:

· procedures used to convert gas concentration measurements to

units of the standard,

· emissions variability associated with the process and control

equipment and the corresponding averaging time for CEMS data

recording and reporting and determining compliance with applicable

standards,

· likelihood of substances within the effluent stream causing

analytical interferences with either CEMS measurements or reference

measurements used for relative accuracy determinations

· effluent conditions such as temperature, pressure, moisture

content, and the presence of other materials within the effluent

stream that may affect the operation and reliability of
instrumentation.

Careful consideration of these and other issues is warranted in

applying the recommendations presented here to other source

categories.

The recommended performance specifications provide the basis

for determining the initial acceptability of the CEMS and the

quality assurance requirements provide a basis for determining the

ongoing acceptability of data and monitoring equipment. The

quality assurance recommendations include criteria for deciding

that a monitoring system is "out-of-control" and state that data

collected during such periods cannot be used to satisfy minimum

data capture (i.e., data availability) requirements. A minimum

data availability requirement has been included in the quality

assurance recommendations. It is recognized that some states may

require higher levels of CEMS availability, or define CEMS

availability in other terms. 

The additional requirements associated with the workgroup

recommendations will increase the costs of CEMS performance tests

and quality assurance activities. However, for many sources the

additional cost will be relatively small since effective CEM

programs which can meet the recommended requirements have already

been developed and implemented. It is hoped that the guidelines

will help avoid costly misunderstandings between the source and the

agency which can result in the purchase or installation of

unacceptable equipment. The incremental costs attributable to the

NESCAUM workgroup recommendations are believed to be a relatively

small fraction of the total costs for MWC facilities.

1. Summary of Performance Specification Recommendations for Gas

CEMS

NESCAUM workgroup recommendations for performance

specifications for SO2 and NOx CEMS, CO CEMS, and HCl CEMS are

presented in Section 2 through 4 of this document, respectively.

The recommendations reference the federal regulations. Major

differences include:

a. Calibration gases are required to be used for daily calibration

checks, performance tests and periodic audits of all CEMS.

Calibration of the entire measurement system is required.

Procedures are included to allow source owners or operators to

demonstrate alternate procedures and alternate methods for

calibration checks and audits. These requirements are designed to

eliminate use of calibration procedures that check only a portion

of the measurement system and procedures that have not been

evaluated and documented by the user.

b. The values of calibration gases used for drift tests and daily

calibration checks must be determined quantitatively. Several

procedures are provided to establish the values of the gases.

These requirements are necessary to assess the accuracy of the

monitoring data on a daily basis.

c. A four-point linearity test must be performed for gas monitors.
This can be done with the two gases used for the daily checks and

two Protocol 1 gases used for quarterly audits. (A three-point

check is required for HCl monitors.) This requirement is necessary

to eliminate the use of non-linear monitoring systems which may be

adjusted to provide the correct response at zero and upscale

calibration check points but do not necessarily provide accurate

data at other concentrations.

d. An additional minimum accuracy specification e.g., mean

difference not to exceed 5 ppm, or equivalent (10 ppm for CO

monitors) is added to prevent the accuracy specifications from

being overly restrictive for those applications where emission

levels are very low. The relative accuracy test procedures are

also clarified to eliminate some of problems that are encountered

in conducting these tests at MWC facilities.

e. A cycle time/response time specification and test procedure is

added for all monitors. The specification for SO2 , NOx, diluent,

and HCl monitors is 15 minutes which is consistent with the EPA

requirements in 40 CFR 60.13. A one-minute cycle time/response

time specification is included for CO monitors since some states

will require reporting of one-minute values for this pollutant.

2. Summary of Quality Assurance Recommendations for Gas CEMS

NESCAUM workgroup recommendations for quality assurance

requirements for all gas CEMS are presented in Section 5 of this

document. The recommendations reference the federal regulations.

Major differences include:

a. Submission of a preliminary monitoring plan to the agency is

required in most cases. The plan should set forth the basic

approach that will be used to comply with the monitoring

requirements. It is hoped that agency review of the plan will help

resolve misunderstandings, unacceptable approaches, and confusion

about the monitoring requirements before costly mistakes occur.

b. A CEMS quality assurance plan should be developed for each

facility. Detailed guidance is provided with respect to the QA

plan content.

c. An annual review of the QA plan and results of its

implementation is required to be performed by the source owner or

operator. The results of this review and changes to the QA plan

are reported to the agency.

d. Routine zero and upscale calibration checks of the monitoring

system must be performed on a daily basis. This requirement is

equivalent to the daily calibration check in 40 CFR 60.13 except

that the procedures recommended here are similar to those described

for the performance specification test.

e. A cylinder gas audit consisting of the four-point linearity

test described in the performance specification recommendations

should be performed each calendar quarter. Only routine

calibration adjustments according to the written procedures in the

QA plan are permitted before the audit.

f. A relative accuracy test should be performed in one calendar

quarter immediately before or after the cylinder gas audit. The
CEMS must pass both tests for performance to be considered

acceptable.

g. A minimum data availability specification of 90 percent of

source operating hours is included. The time required for zero and

upscale calibration checks, cylinder gas audits, and certain QA

activities included in approved plans is not subtracted from CEMS

availability. 

3. Summary of Performance Specification Recommendations for

Opacity CEMS

NESCAUM workgroup recommendations for performance

specifications for opacity CEMS are presented in Section 6 of this

document. The recommendations reference the federal regulations.

Major differences include:

a. All opacity monitors must provide external calibration filter

access to facilitate performance audits.

b. All opacity monitors must provide access to instantaneous or

one-minute opacity measurements in addition to six-minute averages.

c. Calibration error tests must be performed in the field or a

performance audit must be conducted to demonstrate that test

results from the manufacturer are representative of performance of

the installed monitor.

4. Summary of Quality Assurance Recommendations for Opacity CEMS

NESCAUM workgroup recommendations for quality assurance

requirements for opacity CEMS are presented in Section 7 of this

document. The recommendations are similar to the requirements for

gas CEMS except:

a. A opacity monitor performance audit is conducted instead of the

cylinder gas audit that is required for gas monitors.

b. A zero alignment procedure is performed for opacity monitors

instead of the relative accuracy test that is required for gas

CEMS.
SECTION 2

PERFORMANCE SPECIFICATIONS FOR SO2 AND NOx CEMS

AT MUNICIPAL WASTE COMBUSTION FACILITIES

This section describes the NESCAUM workgroup recommendations

for monitor location requirements, equipment and performance

specifications, and corresponding test procedures for SO2 and NOx

CEMS installed at MWC facilities. Specifically, the NESCAUM

workgroup recommends that states consider adopting the EPA

requirements contained in "PERFORMANCE SPECIFICATION 2 -

SPECIFICATION AND TEST PROCEDURES FOR SO2 AND NOx CONTINUOUS

EMISSION MONITORING SYSTEMS IN STATIONARY SOURCES" of 40 CFR 60,

Appendix B revised as of July 1, 1988, with the changes detailed in

Items 1 through 8 below. When emission standards necessitate use

of a diluent monitor (O2 or CO2) to determine emissions in units of

the standard, NESCAUM recommends that states consider adopting the

EPA requirements contained in "PERFORMANCE SPECIFICATION 3 -

SPECIFICATIONS AND TEST PROCEDURES FOR O2 AND CO2 CONTINUOUS

EMISSION MONITORING SYSTEMS IN STATIONARY SOURCES" of 40 CFR 60,

Appendix B revised as of July 1, 1988, with the changes detailed

below.

1. Use of Calibration Gases

A design specification should be added to require that SO2,

NOx and diluent monitors be able to accept calibration gases for

daily calibration checks, performance specification tests, and

periodic quality assurance audits. Furthermore, the design

specification should require that the calibration gas injection

point be in the sample probe or at the probe outlet so that the

entire measurement system is checked when calibration gases are

introduced to the monitoring system. For measurement systems

employing dilution probes or similar devices, the calibration gases

must be introduced prior to the dilution point and in such a manner

that they are diluted to the same extent as the sample gases from

the effluent stream. Similarly, for sample acquisition systems

using aspirators or eductors, the calibration gases must be

introduced prior to these devices even if these components are part

of the sample probe assembly.

Source owners or operators (or instrument vendors) may

demonstrate that alternate daily calibration check procedures or

devices provide results comparable to those obtained by using

calibration gases to check the entire measurement system. For

example, a source owner or operator may elect to demonstrate the

validity of an alternate calibration check procedure for (1)

in-situ monitors that accept calibration gases and which also use

calibration gas cells, or (2) for extractive monitors where daily

calibration checks of the entire system are unnecessarily

burdensome. In such cases, a demonstration can be accomplished by

conducting concurrent calibration drift tests using both the
specified method and the alternate method during the performance

specification test. If the results indicate acceptable monitor

performance with respect to the applicable drift specifications,

the alternate procedure may be used for the daily zero and upscale

checks of the monitor. However, the quality assurance plan must

include (1) a detailed discussion of all assumptions associated

with the alternate procedure, and (2) mandatory procedures for

conducting periodic comparisons of the specified and alternate

calibration methods. Such comparisons should be performed on a

monthly or more frequent basis until the alternate procedure has

been evaluated and documented to the satisfaction of the agency.

Source owners or operators may request approval of alternate

routine calibration check procedures for monitors that cannot

accept calibration gases and alternate procedures for conducting

the linearity and response time tests for these monitors. Source

owners or operators are cautioned that alternate calibration

procedures need to be evaluated carefully and thoroughly and that

a single relative accuracy test at one operating condition does not

provide a sufficient evaluation of the validity of a particular

calibration procedure. The source owner or operator should submit

a written plan to the agency for conducting such a demonstration.

If the plan is approved, the source owner or operator may carry out

the demonstration program and submit a detailed report describing

the alternate procedure, all assumptions associated with the

alternate procedure, the procedures and conditions of the

demonstration, the results of the tests conducted, and appropriate

revisions to the CEMS quality assurance plan, as applicable. The

validity of any alternate procedure would be re-examined during

quarterly accuracy audits.

2. Data Availability and Back-Up Data Recording Devices

All CEMS must operate continuously without repairs,

unscheduled maintenance, or non-routine adjustments during the

performance specification tests to determine calibration drift,

linearity, and relative accuracy. In addition, minimum data

availability specifications are included as QA requirements and are

applicable to the operation of the CEMS after completion of the

performance specification tests. (See Section 5, Quality Assurance

Requirements for SO2, NOx, CO, and HCL CEMS, 8. Minimum Data

Availability Requirements of this document.) 

Most CEMS at MWC facilities will include a computer data

acquisition system that performs various operations including (1)

recording effluent concentration measurements, (2) recording daily

calibration check results, (3) compensation of effluent

measurements for drift, (4) calculation of emissions in units of

the standard, (5) averaging of measurement data, (6) generating

excess emission reports, and (7) interfacing with telecommunication

systems where required by the agency. Data acquisition systems are

inherently monitor- and source-specific and may need to accommodate

diverse reporting requirements of various states, therefore much
flexibility in the design of these systems is needed. When the

data acquisition system is inoperative, many vital CEMS functions

are suspended and data availability is immediately affected.

Source owners and operators are encouraged, but not required, to

include a back-up recording device or other appropriate redundancy

within the data acquisition system to maximize data availability.

Where such devices are used, conformance with the calibration drift

and linearity specifications should be determined based on results

obtained from both the primary data acquisition system and the

back-up recording devices in order to avoid additional testing when

the back-up recording device is placed in service. However,

failure of a performance specification based on data from a back-up

recording device should not necessitate retesting. 

3. Calibration Drift Test and Reference Values

The calibration drift specifications for SO2 and NOx monitors

(2.5 percent of span) and O2 and CO2 monitors (0.5 percent O2 or

CO2) as well as the calibration drift test procedures in

Performance Specifications 2 and 3 should be maintained except that

(1) the calibration drift tests must be performed using calibration

gases or other prior approved alternate calibration procedure, and

(2) the concentration value of the calibration gases must be known.

The values of the calibration gases may be established through the

use of certified reference materials (CRMS), standard reference

materials (SRMS), or EPA Protocol 1 gases. Alternatively,

calibration gas values determined by the gas manufacturer's

certified analysis (i.e., + 2 % of tag value) may be used if the

concentration is checked by direct comparison with Protocol 1

gases, or by triplicate analysis using an appropriate EPA test

method or an equivalent procedure. The direct comparison of tag

values and Protocol 1 gases can be accomplished using the installed

CEMS in most cases.

Comparison with Protocol 1 gases may be accomplished by

introducing both the subject gas, a zero concentration gas and at

least two Protocol 1 gases into an analyzer demonstrated previously

to meet the linearity test specification in Item 4, below.

(Ambient air and two Protocol 1 gases may be used for O2 monitors

which cannot analyze zero gas.) The Protocol 1 gases should

satisfy the audit range specifications of Appendix F, Procedure 1;

however, alternate ranges including at least two Protocol 1 gases

which bracket the concentration value of the subject gas may also

be used, subject to the approval of the agency. The analyzer

responses to all of the Protocol 1 calibration gases shall be used

to construct a calibration curve for the analyzer. The analyzer

response to the subject gas and the calibration curve shall be used

to determine the concentration of the subject gas. If the

difference between the measured concentration and the tag value of

the subject gas is less than 3 percent of the tag value, use the

tag value as the actual concentration. If the difference between

the measured concentration and the tag value is greater than 3
percent of the tag value, repeat all gas injections and check all

calculations. If the difference still exceeds 3=percent of the tag

value, use the measured concentration as the actual concentration.

(See 40 CFR 60, Appendix A, Method 6C, "6.1.2 Alternative Number 2"

for specific requirements for the analysis of SO2 calibration gases

by EPA test methods. Similar procedures may be used for the

analysis of NO and diluent calibration gases. See Method 7E ,

Section 6.1 for analysis criteria for NO calibration gases.)

Calibration drift tests are intended to identify problems that

affect the stability of the monitor calibration; however, such

tests are conducted over a short period and therefore cannot

represent the full range of operating conditions for the CEMS.

Experience has shown that many of the problems resulting in

excessive calibration drift and loss of monitoring data are related

to poorly conditioned electrical power, inadequate or unsuitable

compressed air supply, excessive vibration, ambient temperature

changes, ambient dust loading, and other site-specific application

problems. Source owners and operators are strongly encouraged to

identify these and other problems that may affect CEMS performance

and take appropriate actions to minimize the loss of CEMS data due

to these problems.

4. Linearity Test

A new performance specification and test procedure should be

added to require a four-point cylinder gas audit to demonstrate the

linearity of each pollutant and diluent monitoring channel. The

linearity specification and test procedure applies to the entire

monitoring channel, including the data acquisition system, as

installed and operated at the MWC facility. (A non-linear analyzer

used in conjunction with appropriate adjustments by the data

acquisition system is acceptable.) Source owners and operators are

encouraged, but not required, to have equipment vendors demonstrate

conformance with the linearity specification prior to shipment of

the CEMS to the subject facility. However, the linearity test is

required to be conducted for each CEMS after installation. 

 The linearity test should use the zero and upscale

calibration values used for the daily calibration checks and the

two audit points specified for cylinder gas audits by Appendix F,

Procedure 1. If the high range audit point (i.e., 50 to 60 percent

of the pollutant monitor span) of Procedure 1 is used for the daily

upscale checks, an audit gas of 80 to 90 percent of span should be

substituted for the high range audit point. Protocol 1 gases, CRMS

or SRMS should be used for the two audit points that supplement the

daily calibration checks. Three non-consecutive measurements

should be made for each of the calibration gases (e.g., zero, low,

mid, high, zero, low, mid, high, etc.) 

The linearity specification should require that the mean

difference between the calibration gas value and the monitor

responses at each of the four points be calculated from the three

measurements. The mean difference at all four test points must be
less than 5 percent of span for SO2 and NOx monitors and 0.5

percent O2 or CO2 for diluent monitors.

The linearity test should be performed as soon as practical

before or after the relative accuracy test. Only the routine

calibration drift adjustments are allowed between the two tests.

Other adjustments or repairs to the monitoring system would

necessitate repeating the linearity and the accuracy test. (During

subsequent quarterly audits, only calibration drift adjustments

according to the written procedure contained in an approved QA plan

are allowed prior to the linearity test or the relative accuracy

test.) 

5. Relative Accuracy Test

The workgroup recommends that states maintain the performance

specification test procedures for the relative accuracy test in

Performance Specification 2 with the clarifications described

below. The daily calibration checks should be performed on each

day that the relative accuracy testing is performed and that no

adjustments or repairs to the monitoring system other than the

routine calibration drift adjustments may be conducted. The

distinction between routine adjustments and corrective action for

a malfunctioning CEMS is particularly difficult for the initial

relative accuracy test since there is little or no track record on

which to base decisions and since the QA plan is usually

incomplete. The following approach is recommended to resolve this

issue. Prior to conducting the test, the source operator must

establish (1) the criteria for adjustment of the monitor

calibration, (2) the criteria or schedule for the performance of

routine maintenance activities, and (3) the frequency or criteria

for conducting additional calibration checks. This information

should be made available to the agency observer. The daily

calibration checks should be performed following the normal

procedure before initiating the test and adjustments should only be

made as indicated by the applicable criteria. During the test, the

source may check the calibration at reasonable intervals and abort

the test if unscheduled maintenance or adjustment are necessary.

If corrective action other than routine adjustments are required,

a 24-hour period should elapse to verify that the CEMS drift is

within acceptable limits before a new test is begun. The new test

may begin immediately, subject to the approval of the agency, if it

can be shown that the corrective action or adjustment does not

affect the calibration drift of the CEMS. 

 Performance Specifications 2 and 3 require only that the

relative accuracy test be performed for the entire measurement

system (i.e., pollutant and diluent monitor) in units of the

applicable standard. However, the source owner or operator is

strongly encouraged, but not required, to determine also the

relative accuracy for each monitoring channel in units of

concentration in order to obtain a more complete evaluation of

monitor performance.
Problems in conducting the relative accuracy tests may be

encountered where significant fluctuations in the emission levels

or very low emission levels are encountered. Therefore, both

relative accuracy specifications in Performance Specification 2

(i.e., relative accuracy less than 20 percent of the mean reference

value or less than 10 percent of the standard) should be retained.

Also, an additional specification should be added to provide an

absolute minimum accuracy specification of 5 ppm mean difference

for SO2 or NOx CEMS relative to the test method. (See Appendix A

for a technical discussion of the various accuracy specifications.)

Thus, for a concentration standard corrected to 7 percent O2 the

following accuracy specifications should apply; relative accuracy

less than 20 percent of the mean reference value, relative accuracy

less than 10 percent of the standard, or mean difference less than

5 ppm corrected to 7 percent O2, whichever is least restrictive.

For cases where the emission standard is expressed in units of

lb/MM=Btu, an equivalent absolute accuracy specification may be

calculated using an average or typical diluent concentration. For

example, it can be shown that 5 ppm SO2 at 7 percent O2 is

approximately equivalent to 0.01 lb/MM=Btu using the F-Factors and

conversion values in EPA Method 19. 

For sources subject to an SO2 or NOx percent removal standard

that is more restrictive than the emission standard (or where there

is no absolute emission standard) an implicit emission standard

should be determined as:

Implicit Standard = [1-Percent Removal/100] x Avg. Uncontrolled

Emissions

The implicit emission standard should be used to calculate the

relative accuracy result as "10 percent of the standard." For this

determination, the uncontrolled emissions may be obtained by

averaging all of the reference test data from the relative accuracy

test of the CEMS at the inlet to the control device. 

The relative accuracy test procedures should be clarified to

explicitly prohibit modification of the operation of time-shared

CEMS during the test to increase the sampling frequency, to

minimize the frequency of sample system cleaning (blow-back)

operations or, to reduce the number of locations from which CEMS

samples are obtained. In order to minimize the effects of

fluctuating emission levels, the source owner or operator may

choose (1) to extend the sampling time to at least 1 hour for

integrated sampling methods, or (2) to increase the number of

samples that are obtained during a run for grab sampling methods.

Alternate relative accuracy test procedures for time-shared CEMS

that reduce the number of locations for which reference samples are

obtained may be approved by the agency on a case-by-case basis.

The source owner or operator may use EPA Method 6 or

instrumental Method 6C for SO2 concentration measurements for

relative accuracy tests. Methods 7, 7A, 7C, or 7D or instrumental

Method 7E may be used for NOx concentration measurements, and

Method 3 or=instrumental Method 3A may be used for O2 or CO2
concentration concentration measurements for relative accuracy

tests. NOTE: Methods 7C and 7D may be subject to analytical

interferences when used at MWC sources; the applicability of these

methods has not been established by field testing at this time.

6. Alternate Accuracy Test Procedure

Section 10. Alternative Procedures of Performance

Specification 2 contains procedures for conducting a cylinder gas

audit in place of a relative accuracy test when a waiver of the

relative accuracy test requirement is granted under the conditions

specified in 60.13 (j). According to these regulations, a source

owner or operator may petition the Administrator for a waiver of

the relative accuracy test requirement when the CEMS is not the

compliance method and when the emissions are less than 50=percent

of the standard as determined by a source performance test. The

regulations specify the content of the petition, the conditions

when it may be applied for, and the conditions under which the

waiver may be rescinded.

The Performance Specification 2 cylinder gas audit procedures

are not needed because the same audit test points are already

included as part of the more elaborate linearity test that is

recommended for all CEMS installed at MWC facilities. (See Item 4

above.) As with any requirement, the agency may waive the relative

accuracy test requirement in cases where the emission levels are

very low as indicated by the results of source performance tests or

other independent effluent measurements regardless of whether the

CEMS are used as the compliance method. However, no general

guidance or criteria is provided here for waiving the relative

accuracy test requirement.

7. Cycle Time and Response Time Test

A specification should be added that requires all SO2, NOx,

and diluent CEMS to complete at least one cycle of operation

(sampling, analyzing, and data recording) for each successive

15-minute period, (i.e., a minimum of four samples per hour).

Extractive monitoring systems may be time-shared between two

measurement locations; however, the cycle time requirement must be

met for both measurement locations. (Some states have adopted

regulations or policies prohibiting any time-sharing of monitors at

MWC facilities, and some states will allow time-sharing only as an

emergency backup provision.) 

Source owners and operators are encouraged to install

monitoring systems fully capable of representing emissions from the

facility. The agency should not excuse apparent excess emissions

that may be due to nonrepresentative sampling because of long CEMS

cycle times or minimum CEMS sampling frequencies. In addition,

sources required to install and operate NOx control equipment may

be subject to shorter measurement cycle time specifications in the

future.
A response time test should be added to determine if each

monitoring channel of the CEMS complies with the cycle

time/sampling frequency specification. The average upscale and

downscale response times should be determined from three

repetitions of each test. The greater of the average upscale or

average downscale response times should be reported as the response

time for the system.

 The upscale response time should be determined by injecting

zero gas into the measurement system and then recording the amount

of time required for the system to return to the effluent

concentration after the zero gas injection has been stopped.

Similarly, the downscale response time should be determined by

injecting a high range calibration gas and then recording the

amount of time required for the monitoring system to return to the

effluent concentration after the gas injection is stopped.

Specifically, the response time may be measured as the time

required for the monitor to complete 95 percent of the

concentration step-change occurring after the gas injection is

stopped during each test. For monitoring systems that perform a

series of operations, (purge-blow back, sample, analyze, etc.) the

injection of calibration gases should be timed to produce the

longest response time. 

In many cases, the actual response time of the measurement

system is only a few seconds as compared to several minutes to

perform the necessary cycle of operations. In these cases, it is

often possible to establish conformance with the cycle time

requirement by inspection of the system rather than by injection of

calibration gases. Such determinations are subject to the approval

of the agency.

8. Data Reporting Equipment Specifications

Additional equipment or design specifications may be added by

states to facilitate the specific record keeping and reporting

requirements that may apply. Various state agencies are currently

considering a wide range of alternatives including: automated data

reporting using magnetic media, telecommunication systems that

allow agency representatives to obtain or review data on-demand

from remote locations, and real-time or intermittent telemetry

systems for CEM data and information. No additional guidance is

included because of the diversity of state requirements and

approaches. 
SECTION 3

PERFORMANCE SPECIFICATIONS FOR CARBON MONOXIDE CEMS

AT MUNICIPAL WASTE COMBUSTION FACILITIES

This section describes the NESCAUM workgroup recommendations

for monitor location requirements, equipment and performance

specifications, and corresponding test procedures for CO CEMS

installed at MWC facilities. Specifically, the NESCAUM workgroup

recommends that states consider adopting the EPA requirements

contained in "PERFORMANCE SPECIFICATION 4 - SPECIFICATION AND TEST

PROCEDURES FOR CARBON MONOXIDE CONTINUOUS EMISSION MONITORING

SYSTEMS IN STATIONARY SOURCES" of 40 CFR 60, Appendix B revised as

of July 1, 1988, the Federal Register Vol. 53, No. 204, October

21,1988, and the changes detailed in Items 1 through 8 below. 

Many of the changes that are recommended for CO monitors are

the same as those recommended for SO2 and NOx CEMS. For the

purposes of these discussions it is assumed that the CO monitor is

used to measure emission levels in units of concentration (ppm).

Where a diluent monitor is used to adjust the data to a consistent

basis (e.g., 7 percent O2 or 12 percent CO2) or where data is to be

reported in terms of combustion efficiency, appropriate adjustments

to the recommended requirements should be made. It is assumed that

the upper limit of the CO measurement range (span value) would be

approximately 300 to 500 ppm. Greater measurement ranges may be

needed for facilities using refuse-derived-fuels particularly

during start-up. Alternate measurement ranges may be used subject

to the approval of the agency when emission levels are consistently

much lower than the standard.

1. Use of Calibration Gases

A design specification should be added to require that CO

monitors be able to accept calibration gases for daily calibration

checks, performance specification tests, and periodic quality

assurance audits. In addition, the recommendations regarding where

the gases are introduced to the measurement system, the application

to dilution sampling systems, and the requirements for

demonstrating the adequacy of alternate calibration techniques are

the same as described in Section 2 for SO2 CEMS. 

Special considerations may apply to CO monitors which utilize

a correction procedure to eliminate the influence of CO2. It may

be necessary to use CO calibration gases with a specific

concentration of CO2 to assess monitor performance. Additional

monitor-specific procedures would be needed to verify the accuracy

of the correction procedure. These procedures should be evaluated

and approved by the agency on a case-by-case basis.

2. Data Availability and Back-Up Data Recording Devices

All CEMS must operate continuously without repairs,

unscheduled maintenance, or non-routine adjustments during the
performance specification tests to determine calibration drift,

linearity, and relative accuracy. In addition, minimum data

availability specifications are included as QA requirements and are

applicable to the operation of the CEMS after completion of the

performance specification tests. (See Section 5, Quality Assurance

Requirements for SO2, NOx, CO, and HCL CEMS, 8. Minimum Data

Availability Requirements.) 

Recommendations and suggestions regarding the use and

performance testing of back-up recording devices for CO CEMS are

the same as described in Section 2 for SO2 CEMS.

3. Calibration Drift Test and Reference Values

In many cases, the daily upscale calibration check value

required by Performance Specification 4 (i.e., 50 to 90 percent of

span) is very much greater than both the normal CO operating level

and the level of the emission standard. Calibration checks at

these levels may not represent actual performance of the monitor.

The requirement should be revised to allow the use of an upscale

calibration check value that either (a) approximates the CO

concentration equivalent to the applicable emission limit, or (b)

is within 50 to 90 percent of the span value. Other upscale

calibration check values may be used subject to the approval of the

agency. Source operators may elect to conduct additional checks of

the CO monitor calibration to evaluate the monitoring data for

their own uses.

The calibration drift specification for CO monitors in

Performance Specification 4 (drift not to exceed 5 percent of span

for 6 out of 7 test days) should be changed to restrict drift to

3 percent of span for 7 consecutive days. The more restrictive

limit is consistent with the capabilities of contemporary

instrumentation. Also, the expression of the limit not to be

exceeded for 7 consecutive days is necessary for the implementation

of Appendix F, Procedure 1 control limits.

The drift test procedures in Performance Specification 4

should be maintained except that (1) the calibration drift tests

must be performed using calibration gases or other prior approved

alternate calibration procedure, and (2) the concentration value of

the calibration gases must be known. The specifications and

procedures that may be used for establishing the values of the

calibration gases are the same as described in Section 2 for SO2

CEMS. The suggestion that the source owner or operator identify

application problems that may affect the stability of the CO CEMS

is also the same as for SO2 CEMS.

4. Linearity Test

A new performance specification and test procedure should be

added to require a four-point cylinder gas audit to demonstrate the

linearity of CO monitors. The linearity specification and test

procedures apply to the entire monitoring channel, including the

data acquisition system, as installed and operated at the MWC
facility. (A non-linear analyzer used in conjunction with

appropriate adjustments by the data acquisition system is

acceptable.) Source owners and operators are encouraged, but not

required, to have equipment vendors demonstrate conformance with

the linearity specification prior to shipment of the CEMS to the

facility. However, the linearity test is required to be conducted

for each CEMS after installation. 

 The requirements for the selection of the audit points for

the linearity test and the test procedures for CO monitors are the

same as described in Section 2 for SO2 CEMS. The linearity

specification should require that the mean difference between the

calibration gas value and the monitor responses at each of the four

points be calculated from the three measurements. The mean

difference at all four test points must be less than 5 percent of

span for CO monitors.

The linearity test should be performed as soon as practical

before or after the relative accuracy test. Only the routine

calibration drift adjustments are allowed between the two tests.

Other adjustments or repairs to the monitoring system would

necessitate repeating the linearity and the accuracy test. (During

subsequent quarterly audits, only calibration drift adjustments

according to the written procedure contained in an approved QA plan

are allowed prior to the linearity test or the relative accuracy

test.) 

5. Relative Accuracy Test

The recommended procedures and conditions for the relative

accuracy test are the same as those described above for SO2 CEMS.

In addition, the workgroup recommends that both of the relative

accuracy specifications in Performance Specification 4 (i.e.,

relative accuracy less than 10 percent of the mean reference value

or less than 5 percent of the standard) be retained. Also, an

additional specification should be added to provide an absolute

minimum accuracy specification of 10 ppm mean difference for CO

CEMS relative to the reference test method. Thus, for a

concentration standard the following accuracy specifications should

apply: relative accuracy less than 10=percent of the mean

reference value, relative accuracy less than 5 percent of the

standard, or mean difference less than 10 ppm, whichever is least

restrictive. Where necessary, the 10 ppm mean difference limit may

be converted to an equivalent limit expressed in units of the

applicable standard using the average diluent concentration

measured during the relative accuracy test and applicable

conversion factors.

The relative accuracy test should be performed using Method

10. When the installed CEMS uses a nondispersive infrared (NDIR)

analyzer, Method 10 shall use the alternative interference trap

specified in section 10.1 of the method. Method 10B is an

acceptable alternative to Method 10. The following alternatives
may be approved by the agency in specific cases.

 Alternative 1 - The test may be conducted using Method 10 without

the interference trap if a laboratory interference test is

performed for the analyzer prior to the field test. The laboratory

interference test should include the analysis of SO2, NO, and CO2

calibration gases representing the range of expected effluent

concentrations. Acceptable performance is indicated if the CO

analyzer response to each of the gases is less than 1 percent of

the applicable measurement range of the analyzer.

Alternative 2 - The test may be conducted using Method 10 without

an interference trap, and without a CO2 trap, subject to the

approval of the agency, based on the submission of information

demonstrating the absence of CO2 interference for the test

analyzer. (If this option is chosen, any interferences that are

present will cause the test analyzer to be biased high. There is

also a possibility that the installed monitor would be subject to

the same interference which would not be detected during the

relative accuracy test. The potential for the high bias may be

acceptable to the agency provided that the source owner or operator

accepts the potential bias and cannot later challenge the accuracy

of the data.)

6. Alternate Accuracy Test Procedure

As described in Section 2 for SO2 CEMS, the alternate accuracy

test procedure for CO monitor are not needed since the more

elaborate linearity test is required for all CO monitors installed

at MWC facilities. The agency may waive the relative accuracy test

requirement if the emissions are consistently very low (e.g., less

than 20 ppm) based on source performance test results (i.e.,

"compliance tests") or other independent effluent measurements.

The agency should be cautious in waiving the relative accuracy test

requirement based solely on CEMS data since some analyzers have

been found to respond poorly to low concentrations of CO.

7. Cycle Time and Response Time Test

For sources subject to an emission limit with a one-hour or

shorter averaging period, an additional specification should be

included that requires the CO CEMS to complete at least one cycle

of operation (sampling, analyzing, 

and data recording) for each successive one-minute period, (i.e.,

60 samples per hour) with an allowance of 10=minutes per hour for

cleaning and calibration operations. For sources subject to

limits with longer averaging periods, alternate cycle time

specifications may be established by the agency. A response time

test should be added to determine if the CO monitor meets the cycle

time/sampling frequency specification. The response time test

should be conducted according to the procedures described above for
SO2 CEMS.

CO monitors with response times exceeding the applicable cycle

time specification are acceptable if the longer response time is

due to delay or "lag" time attributable to the sample acquisition

equipment. For these monitors, performance is acceptable if the

time between the analyzer's initial response and the response

equivalent to 95 percent of the actual concentration change is less

than the cycle time specification (regardless of the delay between

the analyzer's initial response and the time that the gas injection

is stopped during the response time test) provided that the total

response time does not exceed 15 minutes.

8. Data Reporting Equipment Specifications

Additional equipment or design specifications may be added by

states to facilitate the specific record keeping and reporting

requirements that may apply. Various state agencies are currently

considering a wide range of alternatives including: automated data

reporting using magnetic media, telecommunication systems that

allow agency representatives to obtain or review data on-demand

from remote locations, and real-time or intermittent telemetry

systems for CEM data and information. No additional guidance is

included because of the diversity of state requirements and

approaches. 
SECTION 4

PERFORMANCE SPECIFICATIONS FOR HCl CEMS

AT MUNICIPAL WASTE COMBUSTION FACILITIES

Some states may require that HCl CEMS be used to monitor

emissions and/or determine HCl control efficiency at MWC

facilities. The NESCAUM workgroup did not address nor attempt to

determine whether HCl CEMS should be installed at MWC facilities.

It is noted that the EPA has not adopted performance specifications

for HCl monitors in Part 60 and has not announced plans to require

HCl monitors at MWC facilities or any other sources regulated under

the New Source Performance Standards. Nevertheless, the NESCAUM

workgroup recommends appropriate monitor location requirements,

equipment and performance specifications, and corresponding test

procedures for HCl CEMS installed at MWC facilities. This section

describes the NESCAUM workgroup recommendations for HCl CEMS

performance specifications based on currently available

information. Changes to these specifications may be appropriate as

additional information and operational experience with HCl CEMS is

obtained. 

For the purposes of these discussions it is assumed that

Performance Specification 2 would serve as a basic model for HCl

requirements. Also, many of the changes that are recommended above

for SO2 and NOx CEMS are also appropriate for HCl CEMS. It is

assumed that HCl monitors would be used to measure emission levels

in units of concentration (ppm). Where a diluent monitor is used

to adjust the data to a consistent basis (e.g., lb/MM=Btu, 7

percent O2, or 12 percent CO2) appropriate adjustments to the

recommended requirements should be made. It is assumed that the

HCl measurement range for controlled emissions would be

approximately 250 ppm and that the measurement range for

uncontrolled emissions would be approximately 1500=ppm.

1. Use of Calibration Gases

A design specification should be added to require that HCL

monitors be able to accept calibration gases for daily calibration

checks, performance specification tests, and periodic quality

assurance audits. In addition, the recommendations regarding where

the gases are introduced to the measurement system, the application

to dilution sampling systems, and the requirements for

demonstrating the adequacy of alternate calibration techniques are

the same as described above for SO2 CEMS. Because of the higher

cost for HCl calibration gases and the amount of gas used by some

of the currently available monitors, it is expected that a

demonstration of an alternate calibration technique would be

attempted for most HCL CEMS applications.

2. Data Availability and Back-Up Data Recording Devices
All CEMS must operate continuously without repairs,

unscheduled maintenance, or non-routine adjustments during the

performance specification tests to determine calibration drift,

linearity, and relative accuracy. In addition, minimum data

availability specifications are included as QA requirements and are

applicable to the operation of the CEMS after completion of the

performance specification tests. (See Section 5, Quality Assurance

Requirements for SO2, NOx, CO, and HCL CEMS, 8. Minimum Data

Availability Requirements of this document.) 

Recommendations and suggestions regarding the use and

performance testing of back-up recording devices for HCl CEMS are

the same as described in Section 2 for SO2 CEMS.

3. Calibration Drift Test and Reference Values

A calibration drift specification for HCl monitors restricting

drift to 5 percent of span for 7 consecutive days should be

established. The drift test procedures in Performance

Specification 2 should be used except that (1) the calibration

drift tests must be performed using calibration gases or other

prior approved alternate calibration procedure, and (2) the value

of the calibration gases must be obtained from the vendors

certified analysis (within three months of the performance test) or

by performing triplicate analysis of the gases using proposed EPA

Method 26. The suggestion that the source owner or operator

identify application problems that may affect the stability of the

monitor is also the same as for SO2 CEMS.

4. Linearity Test

A performance specification and test procedure should be added

to require a three-point cylinder gas audit to demonstrate the

linearity of each HCl monitor. The linearity specification and

test procedure apply to the entire monitoring channel, including

the data acquisition system, as installed and operated at the

particular facility. (A non-linear analyzer used in conjunction

with appropriate adjustments by the data acquisition system is

acceptable.) This test should use the zero and upscale calibration

gas used for the daily calibration checks and an additional audit

point at 20 to 30 percent of span. The recommended procedures for

performing the test are the same as described above for SO2 CEMS

except that Protocol 1 gases are not available for HCl. Therefore,

the concentration value of all three calibration gases should be

determined as described above in Item 3. The linearity

specification should require that the mean difference between the

calibration gas value and the monitor responses at each of the

three points be calculated from the three measurements. The mean

difference at all three test points must be less than 5 percent of

span for HCl monitors.

5. Relative Accuracy Test

The recommended procedures and conditions for the relative
accuracy test are the same as those described above for SO2 CEMS.

The following accuracy specifications are also recommended:

relative accuracy less than 20 percent of the mean reference value,

relative accuracy less than 10 percent of the standard, or mean

difference less than 5 ppm, whichever is least restrictive. For

cases where the emission standard is expressed in units of lb/MM

Btu or corrected to a specified O2 or CO2 concentration, an

absolute accuracy specification equivalent to 5 ppm should be

calculated using an average or typical diluent concentration and

applicable conversion factors. The appropriate procedures for use

in cases where a percent removal standard is more restrictive than

the emission standard are the same as for SO2 CEMS. The relative

accuracy test should be performed using proposed EPA Method=26. 

6. Alternate Accuracy Test Procedure

The same considerations apply to the alternate accuracy test

procedure for HCl monitors as were described above for SO2 CEMS.

In essence, the alternate accuracy test procedure is not needed

since the more elaborate linearity test is required for all HCl

CEMS installed at MWC facilities. The agency may decide to waive

the relative accuracy test requirement if the emissions are

consistently very low as indicated by source performance test

results (i.e., "compliance tests") or other independent effluent

measurements. However, the relative accuracy test should not be

waived based on low concentrations indicated by the HCl CEMS

because of the possibility of significant or total loss of HCl in

the effluent samples within the sample acquisition/sample

conditioning equipment.

7. Cycle Time and Response Time Test

A specification should be included that requires all HCl CEMS

to complete at least one cycle of operation (sampling, analyzing,

and data recording) for each successive 15-minute period, (i.e., a

minimum of four samples per hour). The same considerations apply

to time-sharing of HCl monitors as are described above for SO2

CEMS. A response time test should be conducted according to the

procedures described above for SO2 CEMS.

8. Data Reporting Equipment Specifications

Additional equipment or design specifications may be added by

states to facilitate the specific record keeping and reporting

requirements that may apply. Various state agencies are currently

considering a wide range of alternatives including: automated data

reporting using magnetic media, telecommunication systems that

allow agency representatives to obtain or review data on-demand

from remote locations, and real-time or intermittent telemetry

systems for CEM data and information. No additional guidance is

included because of the diversity of state requirements and

approaches. 
SECTION 5

QUALITY ASSURANCE REQUIREMENTS FOR

SO2, NOx, CO, HCl CEMS

This section describes the NESCAUM workgroup recommendations

for quality assurance requirements applicable to SO2, NOx, CO, and

HCl CEMS installed at MWC facilities. The NESCAUM workgroup

recommendations are similar to and adopt specific parts of 40 CFR

60, APPENDIX F, PROCEDURE 1. QUALITY ASSURANCE REQUIREMENTS FOR GAS

CONTINUOUS MONITORING SYSTEMS USED FOR COMPLIANCE DETERMINATION

revised July 1, 1988. The QA requirements that are adopted must

also be consistent with the applicable performance specifications

and test procedures. Therefore, the specific NESCAUM workgroup

recommendations for QA requirements and procedures described in

Items 1 through 8 below reference the corresponding performance

specification recommendations in Sections 2, 3, and 4 of this

document.

The following definition is used:

Quality assurance consists of the activities and procedures that

are performed by the source owner or operator to ensure that CEM

data meet certain criteria with respect to accuracy, precision,

availability, and representativeness after the successful

completion of the initial performance specification test.

Specific QA requirements for gas CEMS installed at MWC facilities

for the measurement of SO2, NOx, CO, and HCl emission levels and

percent removal are presented in Items 1 through 7 below.

1. Preliminary Monitoring Plan

Each source owner or operator required to install a CEMS for

the measurement of one or more gaseous pollutants or diluent

concentrations should submit a preliminary monitoring plan to the

agency prior to the installation of the monitoring equipment. The

preliminary monitoring plan need not be submitted if a draft CEMS

QA plan is submitted to the agency prior to the installation of the

monitoring equipment. 

Submission of the preliminary monitoring plan is required to

provide an opportunity for identification of misunderstandings

between the agency and the source owners or operators with respect

to the applicable CEMS requirements and acceptable monitoring

approaches during the planning phase of the monitoring program. It

is hoped that the submission of such a plan and review by the

agency will (1) resolve problems attributable to ambiguous

regulations, (2) minimize the likelihood of the purchase and

installation of unacceptable monitoring equipment, and (3) avoid

the need for development of a detailed quality assurance plan

before actual operating experience with the monitoring equipment is

obtained. 

The preliminary monitoring plan should very briefly set forth
the basic approach that will be used to comply with the applicable

CEMS requirements. It should include:

a. The identification, location, and description of the specific

combustor unit(s) (e.g., plant name, unit number, unit size or

capacity, general type of control system, etc.)

b. Identification of the applicable regulations and continuous

monitoring requirements (e.g., EPA NSPS, state regulations, permit

requirements, etc.)

c. Identification of the type of monitor (e.g., extractive, point

in-situ, etc.) the CEMS manufacturer or vendor, and the model

number or other identifying feature of the equipment to be

installed

d. Identification of the analytical technique for each analyzer

that will be used (e.g., NDIR, UV absorption, chemiluminescence,

etc.)

e. Identification and description of the proposed monitoring

location(s) (i.e., position along the effluent path) and

identification of the specific measurement point(s) at each

monitoring location from which samples will be obtained

f. Discussion of plans for time-sharing of extractive monitoring

systems between two or more monitoring locations either as a

permanent installation or as a back-up provision when a particular

monitor is inoperative

g. Identification of the procedures that will be used to convert

measurement data to units of the standard, including specific

conversion factors, assumptions, and equations as applicable

h. Description of any mathematical procedures that will be used

to correct emission measurement data for calibration drift,

interference of other constituents, quenching, or other measurement

phenomena applicable to the proposed measurement system

i. Brief description of the data acquisition system and data

recording devices

j. Identification of any exceptions to the performance

specifications or other applicable monitoring requirements and any

alternate procedures that may require the approval of the agency

2. CEMS Quality Assurance Plan

Each source owner or operator should develop a CEMS quality

assurance plan for each facility. The quality assurance plan

should be submitted to the agency no later than 90=days after

completing the initial successful performance specification test of

the CEMS. At a minimum the quality assurance plan must address the

following specified quality control and quality assessment

subjects:

a. Background information. - - This should include:

· Identification and description of the specific combustor unit(s)

· Identification of the applicable regulations and monitoring

requirements

· Identification and description of the monitoring instrumentation

· Description of the measurement location(s) and sampling points
· Description of the data recording devices and data handling

system

This information is a reiteration and update of information

contained in the preliminary monitoring plan and information that

is usually included in the performance specification test

report(s). It is included to assure that both the user and the

agency are aware of changes to the original plan and the current

status of the monitoring program at the facility.

b. Procedures used to establish proper calibration of the CEMS. -

- These procedures should explain how the monitoring equipment is

adjusted to provide the correct responses both initially and after

repairs or corrective action. The procedures should address the

calibration of both the components and the overall measurement

system. The procedures should also identify assumed parameters

(i.e., conversion factors, effluent moisture content, etc.) that

are important to the fundamental calibration of the monitoring

equipment. Procedures for verifying the validity of mathematical

procedures used to correct or adjust the monitoring data should

also be included.

c. Procedures used for the routine (daily) zero and upscale

calibration checks and criteria for adjustment of the CEMS for

excessive drift. - - For monitoring systems that use calibration

gases for the daily checks, these procedures should describe: 

· Where the gases are introduced to the measurement system 

· How the correct flow rate and pressure for the gas injections

are determined and maintained

· The length of time the gases are injected

· The data display device(s) used to determine the monitor

response

· Any procedures necessary for the interpretation of the data

· The criteria for deciding if adjustments to the monitoring

system are necessary

· The action to be taken when adjustments are needed

These procedures should include specification of the supplier and

type of calibration materials used for the daily calibration checks

and the method used to establish the concentration values of these

materials. 

For monitoring systems that use an alternate method for

performing the routine zero and upscale checks, similar information

describing the procedures is required. The specific requirements

should be addressed in the written plan submitted when applying for

approval of the alternate procedure during the performance

specification test [See also "Item 1. Use of Calibration Gases" in

the recommended performance specifications.]

d. Procedures used for cylinder gas audits (linearity tests) and

relative accuracy tests. - - These procedures should detail how

the accuracy assessments are conducted at the specific facility.

The values of the two Protocol 1 calibration gases used for the

linearity test, the supplier, and the steps taken to ensure that
the certification is current should be described. The specific

procedures for introducing the gases to the monitoring system as

described in Item 2. c (above) for the daily checks should also be

included. For relative accuracy tests, the test methods to be

used, sampling location/sampling points, duration of sampling runs,

procedures for converting the reference data to units of the

standard, and CEMS data interpretation/calculation procedures

should be specified.

e. Quality control procedures including daily and periodic checks

of system or component performance, preventive maintenance

procedures, spare parts inventory, etc. - - These types of

procedures are inherently monitor- and source-specific. However,

detailed written procedures and corresponding data forms have been

found to be effective for identifying developing problems and

promoting consistency and thoroughness in performing daily and

periodic checks of CEMS. Minimum preventive maintenance procedures

are usually specified by the monitor manufacturer and should be

included in the quality assurance plan. The spare parts that

should be available on site depends on the data availability

requirements, delivery time from suppliers or other sources, and

the likelihood of failure of individual components; historical

performance is the best indicator of the parts that may be needed.

The quality control procedures should explain the organization of

QA responsibilities among the various departments/groups or

individuals at the facility.

f. Corrective action procedures for repair, adjustment, or

replacement of the CEMS or its components. - - Corrective action

procedures are often trouble-shooting efforts and are therefore

difficult to describe in sufficient detail to be useful. However,

clear objective criteria for determining when corrective action is

needed based on the results of the required daily checks and

periodic accuracy tests should be included. Additional criteria

related to procedures or checks included as quality control

procedures may also be helpful in resolving developing problems.

This section should also include alternative monitoring procedures

for use when minimum data availability requirements cannot be met

by the CEMS.

g. Procedures used for data reduction, record keeping, and

reporting of CEMS information. - - These procedures should detail

exactly how the CEMS data is handled including:

· methods for correcting data for calibration drift

· specific averaging procedures

· methods of excluding invalid data and calibration data from

emission averages

· equations, constants, and assumptions used to convert

concentration measurements to units of the standard

· provisions for recording process/control system data and reasons

for excess emissions

· provisions for recording CEMS downtime, adjustments, and repairs

· procedures for review and editing of data 
The media, format, and location of all records and all reports to

be submitted to the agency should be specified. The individuals or

groups responsible for maintenance of records, development of

reports, and review of reports should be identified.

3. Quality Assurance Plan Revision

Each source owner or operator should review the QA plan and

all data generated by its implementation at least once each year

and revise or update the plan, as necessary, based on the results

of the annual review. The revised plan must be available for

on-site review by the agency at any time. Within thirty days of

completion of the annual QA plan review, the source owner or

operator must submit a written explanation of all changes (or lack

of changes) to the agency.

The agency may request revision of the QA plan at any time

based on the results of emission report reviews, inspections,

audits, review of the QA plan, or any other information available

to the agency.

4. Routine Zero and Upscale Calibration Checks

Each source owner or operator should perform a zero (or

low-level value between 0=and 20 percent of span) and upscale (50

to 90 percent of span) calibration drift check at least once daily

in accordance with a written procedure contained in the CEMS QA

plan. The daily check procedure must provide a check of the entire

measurement system including sample acquisition equipment, sample

lines, conditioning systems, analyzers, and data recording devices.

The procedure must be accomplished by introducing calibration gases

of the required concentrations in the sampling probe or at the

sampling probe outlet. For measurement systems employing dilution

probes or similar devices, the calibration gases must be introduced

prior to the dilution point and in such a manner that they are

diluted to the same extent as the sample gases from the effluent

stream. Similarly, for sample acquisition systems using aspirators

or eductors, the calibration gases must be introduced prior to

these devices even if these components are part of the sample probe

assembly. The values of the calibration gases may be established

through the use of certified reference materials (CRMS), standard

reference materials (SRMS), or EPA Protocol 1 gases.

Alternatively, calibration gas values determined by the gas

manufacturer's certified analysis (i.e., + 2 % of tag value) may

be used if the concentration is checked by direct comparison with

Protocol 1 gases, or by triplicate analysis using an appropriate

EPA test method or an equivalent procedure. (See recommended

Performance Specifications for SO2 CEMS, Item 3 for specific

procedures for establishing the gas concentrations.)

Source owners or operators may conduct a demonstration of an

alternate calibration check procedure subject to the approval of

the agency. This demonstration may be conducted during the initial

performance specification test or at a later time. (See Section 2,
Performance Specifications for SO2 and NOx CEMS6, "Item 1. Use of

Calibration Gases" for guidance on demonstration of an alternate

method.)

The monitoring system must allow the amount of positive and

negative drift (difference between the analyzer response and

correct value of the calibration gas) to be quantified. At a

minimum, the monitoring system shall be adjusted when the drift

exceeds two times the performance specification limit. (The

recommended calibration drift performance specifications are 2.5

percent of span for SO2 and NOx monitors, 0.5=percent O2 or CO2 for

diluent monitors, 3 percent of span for CO monitors, and 5=percent

of span for HCl monitors.) When adjustments are made, the drift

check should be repeated after the adjustments are completed to

verify that the monitor responds correctly.

The data acquisition system software in some monitoring

systems automatically applies a mathematical correction to the CEMS

emissions data based on the routine zero and span check results.

Some other CEMS utilize an automatic control system for calibration

drift adjustments. Manual adjustment of systems using automatic

adjustments is not required until the drift based on the unadjusted

responses is equivalent to 10 percent of span for the monitoring

channel. These systems must allow determination of (1) the amount

of drift in the unadjusted values, (2) the magnitude of the

correction factor or adjustment that is applied, and (3) the

adjusted system response to the daily zero and upscale calibration

values.

5. Cylinder Gas Audit

A cylinder gas audit (linearity test) should be performed each

calendar quarter using the same procedures and gas specifications

that were used during the initial performance specification test.

The audit should use the two audit points specified by Appendix F,

Procedure 1 in conjunction with the zero and upscale calibration

points used for the daily checks. If the high range audit point

(i.e., 50 to 60 percent of the pollutant monitor span) of Procedure

1 is used for the daily upscale checks, an audit gas of 80 to 90

percent of span should be substituted for the high range audit

point. A three-point audit check is required for HCl monitors.

The same specification used in the performance specification test

should also apply for the quarterly audits. Acceptable performance

is indicated if the mean difference between the monitor responses

and the value of the calibration gas is less than 5 percent of span

at each of the four audit points for SO2, NOx, CO, and HCl

monitors. The acceptance criteria for diluent monitors is 0.5

percent O2 or CO2. If the system fails the cylinder gas audit,

take corrective action and repeat the audit until successful. The

results of the cylinder gas audit should be reported to the agency

with the emissions report for the period during which the audit is

conducted.
6. Relative Accuracy Tests

A relative accuracy test (minimum of nine sampling runs)

should be performed at least once per year using the same

procedures and specifications used in the initial performance

specification test. The relative accuracy test should be conducted

as soon as practical before or after one of the quarterly cylinder

gas audits to demonstrate the validity of the gas calibration

technique and verify assumptions about the calibration procedure.

No adjustments or repairs to the monitoring system other than the

routine calibration drift adjustment according to the written

procedure contained in the QA plan can occur between the cylinder

gas audit and the relative accuracy test. To be considered working

properly, the CEMS must satisfy both the relative accuracy and

cylinder gas audit specifications. If the system fails to meet

either specification, take corrective action and repeat both tests

until successful. The results of the relative accuracy test should

be reported to the agency with the emissions report for the period

during which the test is conducted.

7. Out-of-Control Periods

Criteria for "out-of-control" periods are similar to those

defined in Appendix F, Procedure 1. Specifically, the monitor is

out-of-control if (a) the calibration drift exceeds two times the

performance specification drift limit for five consecutive days,

(b)=the calibration drift exceeds five times the performance

specification limit on any day, (c) the system fails a relative

accuracy test, or (d) the monitor fails a cylinder gas audit

described above in Item 5. Data collected during out-of-control

periods cannot be used to satisfy minimum data availability

requirements. 

8. Minimum Data Availability Requirements

Source owners and operators subject to continuous monitoring

requirements should properly operate and maintain all monitoring

equipment at all times that the source is operational. For sources

where gas CEMS are required for the measurement of controlled or

uncontrolled emissions of SO2, NOx, CO, or HCl, continuous

monitoring data in units of the standard should be available for a

minimum of 90 percent of the source operating hours for each

reporting period (e.g., quarterly). For the purpose of determining

conformance with this requirement, the time required to perform

routine (e.g., daily) zero and upscale calibration checks, and

quarterly linearity tests is included as CEM operating time. The

time required for scheduled or unscheduled CEMS maintenance or

other quality assurance activities is not included as operating

time in the determination of CEMS availability except as may be

specifically allowed in a QA plan approved by the agency. Some

states may require higher levels of CEMS data availability or may

require the use of redundant monitoring devices for all or some

monitoring parameters.
In the event that the installed CEMS can not achieve the

minimum data availability requirement, the source owner or operator

should use alternate monitoring procedures (e.g., back-up monitors,

parameter monitoring, performance testing, etc.) subject to the

approval of the agency. The alternate monitoring procedures are

required to be described in the QA plan. (See Section 5, 2 Quality

Assurance Plan Item f.)
SECTION 6

EQUIPMENT AND PERFORMANCE SPECIFICATIONS 

FOR OPACITY CEMS

AT MUNICIPAL WASTE COMBUSTION FACILITIES

This section describes the NESCAUM workgroup recommendations

for monitor location requirements, design specifications,

performance specifications, and corresponding test procedures for

opacity CEMS installed at MWC facilities. Specifically, the

NESCAUM workgroup recommends that states consider adopting the EPA

requirements contained in "PERFORMANCE SPECIFICATION 1 -

SPECIFICATION AND TEST PROCEDURES FOR OPACITY CONTINUOUS EMISSION

MONITORING SYSTEMS IN STATIONARY SOURCES" of 40 CFR 60, Appendix B

revised July 1, 1988, with the changes detailed in Items 1 through

5 below. 

1. Performance Specification 1 Design Specifications

The design specifications in Performance Specification 1

should be adopted for: peak and mean spectral response, angle of

view, angle of projection, optical alignment sight, simulated zero

and upscale calibration checks, access to external optics, and

automatic zero compensation indicator. In addition, "Section 6.

Design Specification Verification Procedure" of Performance

Specification 1 should be used to determine conformance with the

above design requirements. The optional requirement in Performance

Specification 1, "Section=5.1.9 External Calibration Filter Access"

should be changed to a mandatory requirement to ensure the

capability of auditing the monitor using external calibration

attenuators. 

(Note: The EPA Atmospheric Research and Exposure Assessment

Laboratory, Quality Assurance Division has initiated an evaluation

of the procedures used for the manufacturer's certification of

conformance with the design specifications for opacity monitors.

Revision of Performance Specification 1 requirements or test

procedures may also result from this effort. Among others, future

revisions may include (1) test procedure clarifications, (2)

specifications for uniformity of light beam, (3) specific

procedures for checking the photopic response.)

2. Cycle Time and Measurement Frequency

An additional design specification should be added to require

that all opacity monitors complete a minimum of one cycle of

sampling and analyzing for each successive 10-second period and one

cycle of data recording for each successive 6-minute period or

other period as specified in applicable regulations during normal

operation. This requirement is similar to the 

requirement in 40 CFR 60.13 (e ) (1) and is also consistent with

the response time specification in Performance Specification 1. The
specification should require that the opacity monitoring system

have the capability to display measurements for 1-minute periods or

shorter intervals to facilitate monitor performance evaluations.

3. Data Availability and Back-Up Data Recording Devices

All opacity CEMS must operate continuously without repairs,

unscheduled maintenance, or non-routine adjustments during the

performance specification tests. In addition, minimum data

availability specifications are included as a quality assurance

requirements and are applicable to the operation of the CEMS after

completion of the performance specification tests. (See Section 7,

Quality Assurance Requirements for Opacity CEMS, 8. Minimum Data

Availability Requirements.) 

It is recognized that most MWC CEMS will include a computer

data acquisition system and that when the data acquisition system

is inoperative, many vital CEMS functions are suspended and data

availability is immediately affected. Source owners and operators

are encouraged, but not required, to include a back-up recording

device or other appropriate redundancy within the data acquisition

system in order to maximize data availability. 

4. Performance Specification 1 Performance Test Procedures and

Acceptance Criteria

The Performance Specification 1 criteria should be adopted for

calibration error, response time, conditioning period, operational

test period, and zero and calibration drift. In addition, Section

7,. Performance Specification Verification Procedure should be used

to determine conformance with these criteria. However, the

requirement that allows the calibration error test to be performed

either at the manufacturer's facility or in the field should be

changed. The regulation should allow the source owner or operator

to choose either (1) to conduct the calibration error tests in the

field, or (2) to conduct a performance audit of the monitor during

the operational test period to ensure that calibration error test

results obtained at the manufacturer's facility are representative

of installed CEMS performance. Procedures for conducting a

performance audit are included with the opacity monitor quality

assurance requirements.

5. Data Reporting Equipment Specifications

Additional equipment or design specifications may be added by

states to facilitate the specific record keeping and reporting

requirements that may apply. Various state agencies are currently

considering a wide range of 

alternatives including: automated data reporting using magnetic

media, telecommunication systems that allow agency representatives

to obtain or review data on-demand from remote locations, and

real-time or intermittent telemetry systems for CEM data and

information. No additional guidance is included because of the

diversity of state requirements and approaches.
SECTION 7

QUALITY ASSURANCE REQUIREMENTS

OPACITY CEMS

This section describes the NESCAUM workgroup recommendations

for QA requirements applicable to opacity CEMS installed at MWC

facilities. The QA requirements that are adopted should be

consistent with the applicable performance specifications and test

procedures. Therefore, the specific NESCAUM workgroup

recommendations for QA requirements and procedures described in

Items 1 through 7 below reference the performance specification

recommendations in Section 6 of this document.

The following definition is used:

Quality assurance consists of the activities and procedures that

are performed by the source owner or operator to ensure that CEM

data meet certain criteria with respect to accuracy, precision,

availability, and representativeness after the successful

completion of the initial performance specification test.

The following QA requirements are recommended for opacity CEMS:

1. Preliminary Monitoring Plan

Each source owner or operator required to install an opacity

CEMS should submit a preliminary monitoring plan to the agency

prior to the installation of the monitoring equipment. The

preliminary monitoring plan need not be submitted if a draft CEMS

quality assurance plan is submitted to the agency prior to the

installation of the monitoring equipment. 

Submission of the preliminary monitoring plan is required to

provide an opportunity for identification of misunderstandings

between the agency and the source owners or operators with respect

to the applicable CEMS requirements and acceptable monitoring

approaches during the planning phase of the monitoring program. It

is hoped that the submission of such a plan and review by the

agency will (1) resolve problems attributable to ambiguous

regulations, (2) minimize the likelihood of the purchase and

installation of unacceptable monitoring equipment, and (3) avoid

the need for development of a detailed quality assurance plan

before actual operating experience with the monitoring equipment is

obtained.

The plan should very briefly set forth the basic approach that

will be used to comply with the applicable monitoring requirements.

It should include:

a. The identification, location, and description of the specific

combustor unit(s) (e.g., plant name, unit number, unit size or

capacity, general type of control system, etc.)
b. Identification of the applicable regulations and continuous

monitoring requirements (e.g., EPA NSPS, state regulations, permit

requirements, etc.)

c. Identification of the CEMS manufacturer or vendor, the model

number or other identifying feature of the equipment to be

installed

d. Identification of the proposed monitoring location(s) (i.e.,

position along the effluent path), description of the

transmissometer measurement path orientation at each monitoring

location, measurement path length, and stack exit diameter

e. Discussion of procedures and equipment that will be used to

calculate the opacity of emissions discharged to the atmosphere

where two or more transmissometers are installed in multiple ducts

for a single unit or where emissions from multiple units are

exhausted through a common stack

f. Description of any automatic procedures that will be used to

correct or adjust opacity measurement results for calibration drift

g. Description of the data recording devices that will be used

h. Identification of any exceptions to the performance

specifications or other applicable monitoring requirements and any

alternate procedures that may require the approval of the agency

2. CEMS Quality Assurance Plan

Each source owner or operator should develop a CEMS QA plan

for each facility. The QA plan should be submitted to the agency

not later than 90=days after completing the initial successful

performance specification test of the CEMS. At a minimum the QA

plan must address the following quality control and quality

assessment subjects:

a. Background information. - - This should include:

· Identification and description of the specific combustor unit(s)

· Identification of the applicable regulations and monitoring

requirements

· Identification and description of the monitoring instrumentation

· Description of the measurement location(s) and monitor paths

· Description of the data recording devices and data handling

system. 

This information is a reiteration and update of information

contained in the preliminary monitoring plan and information that

is usually included in the performance specification test

report(s). It is included to assure that both the user and the

agency are aware of changes to the original plan and the current

status of the monitoring program at the facility.

b. Procedures used to establish proper calibration of the CEMS.

- - These procedures should explain how the monitoring equipment is

adjusted to provide the correct responses both initially and after

repairs or corrective action. The procedures should address the

calibration of the transmissometer(s), the data recording devices,

and the overall measurement system. Procedures for verifying the

validity of mathematical corrections or other automatic adjustments
to the monitoring data should be included.

c. Procedures used for the routine (daily) zero and upscale

calibration checks and criteria for adjustment of the CEMS for

excessive drift. - - These procedures should explain:

· How the daily calibration checks are initiated 

· The data display device(s) used to determine the monitor

responses,

· The criteria for deciding if adjustments to the monitoring

system are necessary

· The action to be taken when adjustments are needed

It is particularly important that any assumptions associated

with the calibration check procedure be understood and that any

auxiliary monitor parameters necessary to assess monitor

performance be identified.

d. Procedures for performance audits and zero alignment checks.

- - These procedures should provide any special information

necessary for the conduct of performance audits or the

interpretation of the audit results. Zero alignment procedures

should explain how the monitor is removed from the stack and set up

under clear path conditions or how the test is performed on the

installed monitor during source outages. The specific procedures

used to adjust the simulated zero device and the records of the

zero alignment results and adjustments should be explained.

e. Quality control procedures including daily and periodic checks

of system or component performance, preventive maintenance

procedures, spare parts inventory, etc. - - These procedures are

inherently monitor- and source-specific. However, detailed written

procedures and corresponding data forms have been found to be

effective for identifying developing problems and promoting

consistency and thoroughness in performing daily and periodic

checks of monitoring systems. Minimum preventive maintenance

procedures are usually specified by the monitor manufacturer and

should be included in the quality assurance plan. The spare parts

that should be available on site depends on the data availability

requirements, delivery time from suppliers or other sources, and

the likelihood of failure of individual components; historical

performance is the best indicator of the parts that may be needed.

The quality control procedures should explain the organization of

QA responsibilities among the various departments/groups or

individuals at the facility.

f. Corrective action procedures for repair, adjustment, or

replacement of the CEMS or its components. - - Corrective action

procedures are often trouble-shooting efforts and are therefore

difficult to describe in sufficient detail to be useful. However,

clear objective criteria for determining when corrective action is

needed based on the results of the required daily checks and

periodic audits should be included. 

g. Procedures used for data reduction, record keeping, and

reporting of CEMS information. - - These procedures should detail
exactly how the CEMS data is handled including:

· methods for correcting data for calibration drift, if applicable

· criteria for identifying invalid data 

· provisions for recording process/control system data and reasons

for excess emissions; 

· provisions for recording and tracking CEMS downtime adjustments

and repairs. 

The media, format, and location of all records and all reports

to be submitted to the agency should be specified. The individuals

or groups responsible for maintenance of records, development of

reports, and review of reports should be identified.

3. Quality Assurance Plan Revision

Each source owner or operator should review the QA plan and

all data generated by its implementation at least once each year

and revise or update the plan, as necessary, based on the results

of the annual review. The revised plan must be available for

on-site review by the agency at any time. Within thirty days of

completion of the annual QA plan review, the source owner or

operator must submit a written explanation of all changes (or lack

of changes) to the agency.

The agency may request revision of the QA plan at any time

based on the results of emission report reviews, inspections,

audits, review of the QA plan, or any other information available

to the agency.

4. Routine Zero and Upscale Calibration Checks

Each source owner or operator should perform a zero (or

low-level value between 0=and 20 percent of span) and upscale (50

to 90 percent of span) calibration drift check at least once daily

in accordance with a written procedure contained in the CEMS QA

plan. (This requirement is the same as that contained in 40 CFR

60.13 (d)=(1).) The daily check procedure must provide a system

check of the analyzer internal optical surfaces and all electronic

circuitry including the lamp and photodetector assembly.

The monitoring system must allow the amount of positive and

negative drift (difference between the analyzer response and

correct value of the calibration check devices) to be quantified.

At a minimum, the monitoring system shall be adjusted when the

drift exceeds the performance specification limit, i.e., 2 percent

opacity. (This criteria is twice as restrictive as the criteria in

40 CFR 60.13.) The transmissometer optical surfaces exposed to the

effluent should be cleaned prior to performing the zero and

calibration drift adjustments except for systems using automatic

zero adjustments. When calibration adjustments are made, the drift

check should be repeated after the adjustments are completed to

verify that the monitor responds correctly.

Some opacity monitors use an automatic zero compensation

device to offset dust accumulation on the optical surfaces or other

changes in the electro-optical components. Also, the data
acquisition system software in some monitoring systems

automatically applies a mathematical correction to the monitoring

data based on the zero and upscale calibration check results.

Manual adjustment of systems using automatic adjustments should be

performed when the drift based on the unadjusted responses (or the

magnitude of the adjustment) is equivalent to 4 percent opacity.

These systems must allow determination of the amount of drift in

the unadjusted values or the magnitude of the correction

factor/adjustment that is applied.

5. Performance Audit

A performance audit of each opacity CEMS should be performed

each calendar quarter according to the procedures contained in

"Performance Audit Procedures for Opacity Monitors"

EPA-600/8-87-025, April 1987, or equivalent procedures subject to

the approval of the agency. The criteria contained in the

referenced document for stack exit correlation error, system

faults, zero and span errors, monitor alignment, dust accumulation,

and calibration error should be used to determine acceptable

performance. The results of the performance audit should be

reported to the agency with the emissions report for the period

during which the audit is conducted.

The values of the optical filters used in performance audits

should be checked at least once per year according to the

procedures in Performance Specification 1.

6. Zero Alignment

A zero alignment should be performed at least once per year

unless a particular facility can submit data showing that a

different frequency is appropriate. The zero alignment procedure

involves adjustment of the monitor so that the response to the

simulated zero device coincides with the monitor response to clear

path conditions. The check may be accomplished if clear path

conditions are present during a source outage or by removing the

transmissometer from the stack and setting up the instrument at the

operating pathlength in a clean environment. (General procedures

for performing zero alignment checks are described in Section 9 of

"Performance Audit Procedures for Opacity Monitors.") The amount

of adjustment necessary to accomplish the zero alignment (expressed

as percent opacity) should be reported to the agency with the

emissions report for the period during which the procedure is

conducted.

An external, removable, zero-jig may be used as an alternate

procedure to the zero alignment provided that (1) the zero-jig

setting is established for the specific monitor by comparison of

monitor responses to the zero-jig and to the clear path condition,

(2) the zero-jig is demonstrated to be capable of producing a

consistent zero response when it is repeatedly reinstalled on the

monitor, and (3) the zero-jig is protected when not in use to

ensure that the setting equivalent to the zero condition does not
change. Source owners or operators that use a zero-jig should

perform a zero alignment and check of the zero-jig at least once

every three years.

7. Out-of-Control Periods

Criteria for "out-of-control" periods are similar to those

defined for gas CEMS. Specifically, an opacity monitor should be

considered out-of-control if (a) the calibration drift exceeds the

performance specification drift limit (i.e., 2 percent opacity) for

five consecutive days, (b) the calibration drift exceeds five

percent opacity on any day, or (c) the opacity monitoring system

fails a performance audit. Data collected during out-of-control

periods cannot be used to satisfy minimum data availability

requirements.

8. Minimum Data Availability Requirements

Source owners and operators subject to continuous monitoring

requirements should properly operate and maintain all monitoring

equipment at all times that the source is operational. For sources

where opacity CEMS are required, continuous monitoring data should

be available for a minimum of 90 percent of the source operating

hours for each reporting period (e.g., quarterly). For the purpose

of determining conformance with this requirement, the time required

to perform routine (e.g., daily) zero and upscale calibration

checks, and quarterly performance audits is included as CEM

operating time. The time required for scheduled or unscheduled

CEMS maintenance or other QA activities is not included as

operating time in the determination of CEMS availability except as

may be specifically allowed in a QA plan approved by the agency.

Some states may require higher levels of CEMS data availability.

In the event that the installed CEMS can not achieve the

minimum data availability requirement, the source owner or operator

should use alternate monitoring procedures subject to the approval

of the agency.
APPENDIX

Comparison of Accuracy Specifications

The two basic relative accuracy specifications of Performance

Specification 2 are illustrated in Figure 1. It can be seen that

"20 percent of the reference value" is the least restrictive

criterion when the emission level is greater than 50 percent of the

standard; "10 percent of the standard" becomes the less restrictive

criterion when the emissions are below 50 percent of the standard.

For both of these specifications, the relative accuracy calculation

includes the sum of the mean difference plus 95% confidence

coefficient. 

The recommended 5 ppm mean difference criterion is an absolute

accuracy specification similar to the "10 percent of the standard"

specification. The 5 ppm criterion is less restrictive than the

"10 percent of the standard" criterion when the emission standard

is 50 ppm because the confidence coefficient is eliminated. At

lower emission standards the difference between the two criteria

becomes more significant and the 5 ppm criterion is the less

restrictive. The various relative accuracy specifications are

illustrated in Figure 2 for emission standards of 50=ppm and 30

ppm. The recommended 5 ppm mean difference accuracy specification

attempts to reflect the limitations associated with the reference

test procedures, the CEMS measurement capability, and the relative

accuracy tests at sources with fluctuating emission levels. These

technical limitations are independent of the level of the emission

standard. Similarly, the 5 ppm criterion is also independent of

the level of the emission standard. 

It can be shown that the proposed NSPS MWC SO2 emission limit

of 30 ppm corrected to 7 percent O2 corresponds to about 0.07 lbs.

SO2/MM Btu. Thus, the alternate "20 percent of the standard"

accuracy specification of Performance Specification 2 could be

applied. However for the proposed NSPS standard, this limit

corresponds to 6 ppm and includes the confidence coefficient. This

is probably more restrictive than the recommended 5 ppm mean

difference criterion without the confidence coefficient and it is

also dependent on the emission standard. The "average" or

"typical" contribution of the confidence coefficient to the

relative accuracy result could be determined by statistical

analysis of test results at MWC facilities. However, it seems

unlikely that the confidence coefficient contribution is less than

1 ppm. Thus, the 5 ppm mean difference limit is less restrictive

than the "20 percent of the standard" criteria.
Figure 1. Performance Specification 2,Relative Accuracy Specifications

ACTUAL EMISSIONS

(Percent of Standard)

10 20 30 40 50 60 70 80 90 100

10

20

30

40

50

60

70

80

90

100

110

120

Figure 1Redrawn to be compatible with Wordperfect file
NOTE: I had to redraw the following figures because they were done orginally on a

MAC. They are not quite as precise as they should be. If you want a hard copy of

the orginals, send me a Message on the BBS . Terry Harrison
30 ppm

STD

30 ppm STD

Transition

+

(assumes 2.5 ppm confidence coefficient)

Equivalent 5 ppm Mean Difference Accuracy Criterion

-

10 % of 50 ppm STD

(i.e. 5 ppm) +

-

10% of 30 ppm STD (i.e. 3 ppm)+

-

50 ppm STD

Transition

50 ppm 

STD

+

-

10 20 30 40 50 60 70 80

ACTUAL EMISSIONS

(ppm)

Figure 2. Example Accuracy Specifications for 30 ppm and 50 ppm Standards

10

20

30

40

50

60

70

80

Figure 2 Redrawn to be compatilbe with Wordperfect file.