Performance Specification YY: 

Specifications and Test Procedures for X-Ray 

Fluorescence Based Multi-Metals Continuous 

Emission Monitoring Systems at Stationary Sources 

Prepared by: 

Cooper Environmental Services, LLC 

10180 SW Nimbus Blvd Suite J6 

Portland, Oregon 97223 

Revision: 1.0 

 June, 2005 

 
Performance Specification YY: 

Specifications and Test Procedures for X-Ray 

Fluorescence Based Multi-Metals Continuous 

Emission Monitoring Systems at Stationary Sources

Prepared by:___________________________________ Date:_________

Krag A. Petterson, Environmental Scientist 

Reviewed by: ___________________________________ Date:_________ 

Cay A. Yanca, Environmental Scientist 

Reviewed by: ___________________________________ Date:_________ 

Bruce E. Johnson, QA Manager 

Approved by: ___________________________________ Date:________ 

John A. Cooper, Director 
Executive Summary 

Performance Specification YY details the performance requirements for a multi-metals

continuous emissions monitor that utilizes x-ray fluorescence (XRF) as an analytical 

technique. Each XRF based multi-metals CEMS must meet the criteria for accuracy, 

stability, and instrumental response laid out in this document. In addition, every XRF multimetals CEMS must meet the installation requirements in PS-YY and the on-going quality 

control and quality assurance procedures set forth in procedure Z if it is used for emissions 

compliance purposes. 

Specifications for XRF-Based Multi-Metals CEMS (PS-YY) Page i of iv 
List of Symbols 

bo = The y intercept of the best fit line 

b1 = The slope of the best fit line 

CAi = X-ray fluorescence calibration accuracy 

C Ci = Corrected CEMS concentration for the ith element 

CEMS Ci = The concentration of the ith element as reported by the CEMS 

CEM Ci = The average reported concentration of the CEMS for the ith element 

PT CFi = Correction factor for percent transport for the ith element 

RB CFi = The relative bias correction factor for the ith element 

L Ci = The emission limit of the ith element 

S Ci = Concentration of the ith element at the stack 

sm Ci = Concentration of the ith element at the sampling module or as reported by the 

XRF multi-metals CEMS. 

di = Difference between two paired measurements 

d = Arithmetic mean of differences 

FS = Full scale value of your CEMS volume (or flow) measurement device 

0 Li = The value of the ith element on the zero standard determined immediately after 

calibration 

cem Li = The value of the calibration check standard reported by your CEMS 

cemo Li = The measured CEMS response to the zero standard for the ith element 

cemu Li = The measured CEMS response to the ith element in the upscale standard

std Li = The known value of the calibration check standard 

u Li = The calibrated value of the ith element of the upscale standard

n = Number of data points 

PTi = The percent transport of the ith element

PT i = Average percent transport for the ith element 

PRBi = Relative Bias of the ith element 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page ii of iv 
RM Ri = The average of the reference method measurements for the ith metal 

PRSDi = The relative percent standard deviation for the ith metal 

r = The correlation coefficient 

SDi = The standard deviation of differences for the ith element 

Vcemr = Sample gas volume (or flow) as measured by the CEMS volume check device 

VD = Volume drift 

Vm = Volume (or flow) reported by your multi-metals CEMS 

UDi = The upscale drift of the ith element on your CEMS in percent. 

x = Arithmetic mean 

xi = Value of each data point 

yi = CEMS reported concentration for the ith element 

ZDi = The zero drift of the ith element on your CEMS in percent 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page iii of iv 
Table of Contents 

1.0 Using PS-YY ................................................................................................................ 1 

1.1 What is the purpose and applicability of Performance Specification YY? .............. 1 

1.2 What will be discussed in PS-YY? ........................................................................... 1 

1.3 What are the installation and pre-performance specification test requirements? ..... 2 

1.4 What special definitions apply to PS-YY? ............................................................... 3 

2.0 Interferences, Safety, and Equipment Requirements.................................................... 5 

2.1 Are there any potential interferences for my XRF multi-metal CEMS? .................. 5 

2.2 What do I need to know to ensure the safety of persons using PS-YY? .................. 5 

2.3 What equipment and supplies do I need? ................................................................. 5 

2.4 What regents and standards do I need?..................................................................... 6 

3.0 Performance Evaluation Procedures and Reporting ..................................................... 6 

3.1 What is the purpose of the initial performance specification tests and what is 

required to perform the tests? ............................................................................................... 6 

3.2 How do I report the results of the initial performance specification test? .............. 12 

4.0 Performance Criteria and Calculations....................................................................... 13 

4.1 What are the performance criteria for my XRF multi-metals CEMS? ................... 13 

4.2 What calculations, equations, and data analyses are needed? ................................ 14 

5.0 Other Requirements and Information ......................................................................... 20 

5.1 What quality control measures are required?.......................................................... 20 

5.2 What calibration and standardization procedures must I perform? ........................ 20 

5.3 What pollution prevention procedures must I follow? [reserved] .......................... 20 

5.4 What waste management procedures must I use?................................................... 20 

5.5 What reference tables and figures are relevant to PS-YY?..................................... 20 

5.6 What references apply to PS-YY? .......................................................................... 30 

Table 1

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page iv of iv 
1.0 Using PS-YY 

1.1 What is the purpose and applicability of Performance Specification YY? 

1.1.1 Purpose 

The purpose of Performance Specification YY is to establish the performance 

requirements that must be met by a multi-metals continuous emission monitoring 

system (CEMS) that utilizes x-ray fluorescence (XRF) to determine metal 

concentrations in stationary sources. Assurance of the continuing quality of the CEMS 

data may be achieved by following the procedures defined in Procedure Z – XRF 

Based Multi-Metal CEMS Quality Assurance Procedures. 

1.1.2 Application 

PS-YY applies to you if you intend to use an XRF multi-metals CEMS for purposes of 

establishing compliance with federal regulations for metal emissions from stationary 

sources. 

1.1.3 Measurement Capabilities 

A multi-metals CEMS must be capable of measuring total concentrations of at least 

two metals in the units of the applicable standard or in units that can be converted to 

units of the applicable standard.

1.1.4 Other Monitoring

If your XRF based multi-metals CEMS is capable of reporting a metal concentration in 

the units of the existing regulation no additional monitoring is necessary. If your 

CEMS does not report concentrations in the units of the existing standard then other 

monitoring (e.g., oxygen, temperature, and pressure) are necessary to convert the units 

reported by your CEMS to the units of the standard.

1.2 What will be discussed in PS-YY? 

PS-YY covers two basic topics: (1) the instrument requirements for a XRF based multimetals CEMS and (2) the requirements that each XRF multi-metals CEMS must meet during 

the initial performance specification test. 

1.2.1 Instrument Requirements 

A multi-metals CEMS must be able to accurately report the concentrations of at least 

two metals. It may do so by extracting a representative sample (path or point sampling 

may be used if the sample is representative) of stack effluent and capturing the metal 

analytes of interest on a medium. The CEMS must have a cycle time that is less than 

one third the period of the applicable standard. The range of the instrument must be 

from 10 percent to at least 400% of the applicable regulation as determined by field or 

Specifications for XRF Based Multi-Metals CEMS (PS-YY)) Page 1 of 30 
laboratory tests. Finally, the instrument or operator must be able to perform daily 

upscale, blank, and flow quality assurance checks to ensure the accuracy, precision, 

and stability of the instrument and its data. 

1.2.2 Initial Performance Specification Tests 

The purpose of the initial performance specification test is to establish the stability, 

accuracy, and precision of your XRF multi-metals CEMS. The performance 

specification test can be divided into two phases: (1) the stability test, and (2) the 

accuracy test. 

The stability test consists of a seven day check of the zero and upscale calibration drift 

and is done prior to the accuracy testing. For the accuracy tests, three methods of 

metals generation (quantitative spiking, non-quantitative spiking, and stack operation) 

and two methods of data analysis (percent relative bias, and linearity) are available. 

The sampling and XRF modules of your CEMS may also be tested separately from

your stack sampling interface. Some options may be better than others depending on

your multi-metals CEMS, or the conditions existing at your stack. 

1.3 What are the installation and pre-performance specification test requirements? 

1.3.1 Installation Requirements 

The sampling location of an XRF multi-metals CEMS should be downstream of all 

pollution control equipment at a position where the metals concentrations are directly 

representative or can be corrected so as to be representative of total emissions from the 

stationary source. It is recommended that the sampling location be at least two 

equivalent diameters downstream of the nearest control devices, point of pollution 

generation, bend, or other point at which a change in pollutant concentration or flow 

disturbance may occur. The sampling location is also recommended to be at least two 

equivalent diameters upstream from the exhaust. The equivalent diameter is calculated

according 40 CFR Part 60, Appendix A, Method 1, Section 2.1i

. 

Either point or path sampling may be used. For point sampling the measurement point 

should be no less than 1.0 meter from the stack or duct wall or located over the 

centroidal area of the stack or duct cross section. For a path sampling CEMS the 

effective measurement path should be (1) totally within the inner area bounded by a 

line 1.0 meter from the stack or duct wall, or (2) have at least 70 percent of the path 

within the inner 50 percent of the stack diameter or duct cross section. The sample 

collection and instrumental analyzer portions of your XRF multi-metals CEMS may be 

located any distance from the sampling point provided the transmission efficiency from

the sampling point to the sample collection point can be determined and meets the 

criteria outlined later in this performance specification. It is also recommended that the 

sampling probe for your multi-metal CEMS be located at point without stratification. 

You may test for stratification at the proposed CEMS sampling point by using either 

PM (as outlined in PS-11), velocity tests as described in Method 2ii, or metals 

concentrations using Method 29 or an acceptable alternative. 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 2 of 30 
1.3.2 Sampling Requirements 

Your multi-metal CEMS should sample from the source at a flow rate which is within 

10 percent of true isokinetic. If your multi-metal CEMS does not maintain an 

isokinetic sampling rate you must use actual site-specific data or data from a similar 

installation to prove to us, the State, and/or local enforcement agency that isokinetic 

sampling is not necessary. 

1.3.3 Pre-Test Preparation Requirements and Suggestions 

Prior to the initial performance specification test you need to ensure that your multimetal CEMS data logger accurately records emissions levels as well as signals (flags) 

that indicate both normal and abnormal operation. Prior to start of the seven day 

stability test the daily drift measurements (upscale and zero values) should be 

monitored to ensure that the instrument is operating in an appropriate and stable 

manner. We recommend that you use your XRF multi-metal CEMS for a sufficient 

length of time to become comfortable with its operation prior to the start of the initial 

performance specification test. 

1.4 What special definitions apply to PS-YY? 

Calibration Drift: The difference in the CEMS output readings from the established 

reference value after a stated period of operation during which no unscheduled maintenance 

or adjustment took place. 

Cycle Time: The time between when the stack gas first comes in contact with the 

concentrating media and when the concentration value for that sample is reported. 

Data Recorder: The portion of the CEMS that provides a record of analyzer output 

including metal concentrations, flags which indicate normal operation, and flags indicating 

abnormal operation. The data recorder may record other pertinent data such as effluent flow 

rates, and various instrument temperatures.

Diluent module: The part of the CEMS in which any diluent is added and measured. 

Drift Calibration Standard: A standard containing a constant amount of metal used to 

establish the drift in the x-ray fluorescence module response. 

Emission Limit: The emission limit for a single metal is equal to the maximum amount 

allowed under the applicable regulation for its category assuming all of the other metals in its 

category were not present. 

Element of Opportunity: An element that is present in the stack effluent and can be used to 

establish transport efficiency. 

Instrument Measurement Range: The range of metal concentrations the instrument can 

reliably measure from the lowest concentration to the highest. The instrument measurement 

range may be different for different metals. If the upper end of the measurement range is 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 3 of 30 
more than four times the emission limit, the upper limit does not need to be definitively 

established.

Path Sampling CEMS: A CEMS that samples the source effluent along a path greater than 

10 percent of the equivalent diameter of the stack or duct cross section. 

Point Sampling CEMS: A CEMS that samples the source effluent at a single point. 

Non-Quantitative Spiking: The process of introducing an unknown amount of metal or 

metals into the effluent or sample stream. 

Quantitative Spiking: The process of introducing a known amount metal or metals into the 

effluent or sample stream. 

Percent Relative Bias: The difference between a reference value and the CEMS measured 

value divided by the reference value. 

Reference material: A material of known value used to check the calibration drift of your 

XRF multi-metal CEMS. 

Sample Interface: The portion of the CEMS used for one or more of the following: sample 

acquisition, sample transport, sample conditioning, or protection of the monitor from the 

effects of stack gas. 

Sampling module: The portion of an x-ray fluorescence based multi-metal CEMS that traps 

the metals and delivers them to the XRF module. 

Spiking: The process of introducing metals into the effluent stream or the sampling stream. 

Transport Efficiency: The percent of metal that is transported from the sample probe to a 

point as close as possible to the sampling module. 

Upscale Drift: The upscale drift is the difference in the reported value for the upscale 

reference from its value at the last calibration, divided by the value at the last calibration. It 

is used to monitor the stability of the x-ray fluorescence analysis. 

X-Ray Fluorescence (XRF) Module: The portion of an XRF based multi-metal CEMS 

which identifies and measures metal masses or concentrations using x-ray fluorescence. 

XRF Multi-Metals Continuous Emission Monitoring System (CEMS): All of the 

equipment required for determining metal concentrations using x-ray fluorescence as an 

analytical technique. The system may consist of several major subsystems including but not 

limited to the following the sample interface, the x-ray fluorescence module, diluent module, 

data recorder, sampling module and volume measurement module. 

Zero Drift: The zero drift is the difference in the CEMS readings for the zero reference from

their values after the most recent calibration, divided by the emission limit for each element. 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 4 of 30 
2.0 Interferences, Safety, and Equipment Requirements 

2.1 Are there any potential interferences for my XRF multi-metal CEMS? 

There may be interferences arising from the x-ray fluorescence analysis, the trapping media, 

or from condensation in the effluent gas. Check with your multi-metal CEMS manufacturer 

to find out more about potential interferences. 

2.2 What do I need to know to ensure the safety of persons using PS-YY? 

People using PS-YY may be exposed to hazardous material, operational hazards, and 

hazardous site conditions. PS-YY does not address all the safety issues associated with its 

use. It is your responsibility to ensure the safety of persons using PS-YY. Some helpful 

references may include the CEMS manual, the CEMS manufacturer, other reference 

methods, and on-site safety regulations. 

2.3 What equipment and supplies do I need? 

2.3.1 Equipment for the CEMS 

1. Sample interface: This portion of the CEMS must present a sample of source 

effluent to the sampling module that is directly representative or can be 

corrected so as to be representative of source. To accomplish this, the sample 

interface may contain, among other things, heaters or heating systems, and 

dilution air. 

2. Sampling module: The sampling module must collect and trap all the analytes 

of interest from a representative sample of stack effluent without significant 

loss. The trapped analytes then must be presented to the XRF module.

3. XRF module: The XRF module uses x-ray fluorescence to determine the mass 

or concentration of metal captured by the sampling module.

4. Volume measurement module: This portion of the CEMS measures the 

volume of source effluent from which the metal analytes were captured in the 

sampling module. This volume along with the data from the XRF to determine 

concentration of source effluent. 

5. Diluent Module: If your multi-metals CEMS uses a diluent such as air or

nitrogen it is added to the effluent sample and measured using the diluent 

module.

6. Quality assurance and quality control materials: Your multi-metal CEMS 

must possess the necessary equipment to perform daily upscale and zero 

checks. Your multi-metal CEMS must also possess the equipment to perform a 

daily check of the sample volume at normal sample flow rates.

7. Data recorder: Your XRF multi-metal CEMS must be able to record metal 

concentrations and instrument status signals (flags). 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 5 of 30 
2.3.2 Other Equipment Needed for the Performance Specification Test 

PS-YY does not specify all the equipment and supplies necessary for the performance 

specification tests. Some of this information is included in the applicable reference 

methods (e.g., Method 29 or an acceptable alternative). 

2.4 What regents and standards do I need? 

2.4.1 Zero Drift Reference 

Your multi-metals CEMS must include a standard for the measurement of the daily 

zero drift. This reference should produce a CEMS response indicating the absence of

metals. If this is not feasible this standard should produce a value between zero and 

20% of the emission limit for at least two elements measured by your XRF multimetals CEMS when the instrument is operating appropriately. 

2.4.2 Upscale Drift Reference 

The reference for the upscale drift check should generate a response for at least one 

metal from each condition used in the XRF analysis. This response must be at least 80 

percent of the emission limit. 

2.4.3 Volume Drift measurement device 

During the initial performance specification test the volume measurement must be 

compared on a daily basis against an internal volume or flow measurement device. 

This volume or flow measurement device must be calibrated independently of the 

sample volume or flow measurement device and must be as accurate or more accurate 

than the sample volume or flow measurement device. 

2.4.4 X-ray Fluorescence Calibration Check Standards 

Your XRF multi-metals CEMS must include a means of checking the x-ray 

fluorescence calibration against an external standard. NIST traceable thin film

standards are an example of a suitable x-ray fluorescence calibration check standard. 

3.0 Performance Evaluation Procedures and Reporting 

3.1 What is the purpose of the initial performance specification tests and what is required 

to perform the tests? 

The purpose of the initial performance specification tests is to determine the bias, precision, 

stability, and cycle time of your multi-metal CEMS. 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 6 of 30 
3.1.1 Pretest Preparation 

Prior to the start of your initial performance specification tests you must be sure that 

your CEMS is installed according to the specifications laid out in this document. After 

installing your XRF multi-metals CEMS we recommend that you use the CEMS for a 

period of time to familiarize yourself with its operation. We also recommend that you 

conduct daily checks of the zero and upscale drift to verify that the instrument is 

functioning properly. When you are confident that the instrument is performing 

satisfactorily it is time to prepare for the initial performance specification tests. 

3.1.2 X-ray Fluorescence Calibration Check 

If your CEMS measures more metals for compliance purposes than will be evaluated 

during the CEMS accuracy testing described later in this document you must perform a 

calibration check of the x-ray fluorescence module for these additional metals. During 

the calibration check you must challenge the x-ray fluorescence module with a standard 

or standards for each metal measured by your XRF multi-metal CEMS. Each metal 

must be measured at least three times and the error is calculated according to 

Equation 13 for each measurement. The average error of the three measurements 

must be less than 10% of the calibration standard’s value for each metal, if not your 

CEMS may not be properly calibrated. The x-ray fluorescence calibration check may 

occur at anytime during the initial performance specification test. . 

3.1.3 Stability – The 7-day Calibration Drift Tests 

Prior to the start of the accuracy test you must perform a calibration drift test for a 

period of at least seven days. The purpose of this test is to verify that the instrument 

operation is stable. During the calibration drift test period you must determine the 

magnitude of the zero calibration drift (as calculated in Section 4.2.9), the upscale 

calibration drift (as calculated in Section 4.2.8), and the volume (or flow) drift 

(calculated using Equation 14) at least once each day. During the stability tests no 

adjustments or calibrations may be made to the CEMS. The results of the stability test

must be reported along with the results of the accuracy tests. 

3.1.4 CEMS Accuracy 

The accuracy of your XRF multi-metal CEMS may be determined using one of the 

following four options. 

1. Option A: Linearity test of the entire CEMS 

2. Option B: Linearity test of the XRF and sampling modules separately from the 

sample interface. 

3. Option C: Relative bias test of the entire CEMS. 

4. Option D: Relative bias test of the XRF and sampling modules separately 

from the sample interface. 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 7 of 30 
There are also several options for generating the metals that will be analyzed by your 

multi-metal CEMS including, metals that are generated as a by-product of normal stack 

operation, quantitative spiking, and non-quantitative spiking. Regardless of the 

generation option you choose you must be able to produce concentrations for some of 

the analytes of interest at 80 to 120 percent of the emission limit. All of the CEMS and 

reference method measurements must be conducted while sampling flue gas. 

You do not need to test every metal that your CEMS measures, however, you must 

generate at least one metal from each category of metals measured by your CEMS for 

the accuracy tests. For instance, if your XRF multi-metals CEMS measures semivolatile, low volatile, and high volatile metals you must test at least one metal from

each of those categories. (Low volatile metals may also be used to verify the capture 

efficiency and detection of non-enumerated metals). You must also prove that the 

XRF module is properly calibrated to measure the elements that are not being 

measured during the accuracy test by following the procedures described in Section 

3.1.2. The test requirements for each option are explained below and summarized in 

Table 1. 

• Linearity Test Requirements (Options A and B): The bias and precision of 

your XRF multi-metals CEMS may be determined by checking the linearity of 

the instrument response over a series of concentrations. If quantitative spiking 

is used, then the concentration of the aerosol is paired with a reported CEMS 

concentration acquired at the same time. Each data point is then plotted with 

the spiked concentration on the X axis and the reported CEMS concentration on 

the Y axis. If either non-quantitative spiking or stack by product is used, then 

the reported CEMS concentration is plotted on the Y axis versus the 

concentration reported by method 29 or a suitable alternative. 

Linear least squares regression analysis is then used to fit the data points to a 

line. If you challenge only the XRF module and the sampling module the slope 

of this line, which is an indication of the accuracy of your XRF multi-metal 

CEMS, is required to be between 0.85 and 1.15 for each metal. The coefficient 

of correlation must be greater than 0.90 and is an indication of the precision of 

your multi-metal CEMS. Finally, the intercept of this best fit line must be less 

than 20% of the applicable emission limit. If you challenge the entire CEMS 

system and do not meet the slope or intercept criteria you must apply a 

correction factor according to the procedures in Section 4.2.12. You are, 

however, still required to have a correlation coefficient of 0.90 or greater. 

To perform the linearity test you must be able to generate at least three 

concentration levels for one metal from each class of metals (high volatile, low 

volatile and semi-volatile) measured by your CEMS. The three levels must 

incorporate at least a two fold concentration change and one level must be 

between 80 and 120 percent of the emission limit. You may acquire a blank 

sample if you wish, either by sampling ambient air, or by operating the source 

in such a way that metals are not produced (e.g., burning only natural gas). At 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 8 of 30 
least three measurements are required at each concentration level and a total of 

15 measurements are required overall. You may make additional 

measurements, however, you must report all the results. If you are not using 

quantitative spiking you must make 15 corresponding measurements using 

method 29 or a suitable alternative. We recommend using duel trains for the 

reference method measurement to identify and screen the reference method data 

for imprecision and bias. 

Additional requirements for each of the two linearity test options are outlined 

below. You may also want to refer to figures 1 through 8 for guidance on 

which option to choose. 

Option A: Total CEMS Linearity

In option A the entire CEMS system is challenged during the linearity tests. 

Any one of the three methods of metals generation may be used during the test. 

Some of the testing requirements associated with metals generation are outlined 

below 

1. Metals generated as a result of stack operation

If metals for the test are generated as a result of stack operation you must 

measure the concentration of the metals in the stack using method 29 or a 

suitable alternative and compare the values with those reported by your 

CEMS. We recommend using dual reference method trains to screen the 

reference method for precision and bias.

2. Non-quantitative spiking

You may either spike non-quantitatively into the stack or duct itself or into 

the transport system as close as possible to the sample probe. If you spike 

into the source you must measure the concentration in the source using 

method 29 or a suitable alternative. This measurement is then compared to 

the result of your CEMS. If you choose to spike into the transport line you 

must measure the concentration immediately downstream of the spike point 

with a method 29 or a suitable alternative and compare that measurement 

with the concentration reported by your CEMS.

3. Quantitative Spiking

You may spike a quantitative aerosol directly into the source or into the 

transport line as close as possible to sample probe. Either way the known 

spiked concentration is compared with that measured by the CEMS. 

Option B: Linearity for Sampling and XRF Modules Only

In option B only the sampling and XRF modules of your multi metals CEMS 

are challenged with a linearity test. You must also complete a transport 

efficiency test along with the linearity test. The procedures for performing a 

transport efficiency test are described in section 3.1.5. The procedures for 

option B associated with each metals generation option are listed below. 

1. Metals generated as a result of stack operation

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 9 of 30 
If metals concentrations for the accuracy test are generated as a result of 

stack operation you must measure the concentration of the metals as close as 

possible to the sampling module using method 29 or a suitable alternative 

and compare the values with those reported by your CEMS. We recommend 

using dual reference method trains to screen the reference method for 

precision and bias.

2. Non-quantitative spiking

You may either spike non-quantitatively into the stack or duct itself or into 

the transport system. Either way you must measure the concentrations of the 

analytes as close as possible to the sampling module and compare that 

concentration with that reported by your multi metal CEMS.

3. Quantitative Spiking

You must spike at a location as close as possible to the sampling module and 

compare the known spiked concentration with that reported by your CEMS. 

• Relative Bias Test Requirements (Options C and D): There are two relative 

bias options available: one that challenges the entire CEMS and one that 

challenges the sampling and XRF modules separately from the sample 

interface. Either option requires at least 12 CEMS measurements be made at a 

concentration level 80 to 120 percent of the emission limit for a metal from 

each category of metals analyzed by your XRF multi metal CEMS. If you are 

not using quantitative spiking you must also have at least 12 corresponding runs 

of method 29 or a suitable alternative at this concentration level. We

recommend using dual trains for the reference method to screen the data for 

imprecision and bias. 

Additionally, for at least one metal measured at the emission limit or for a 

surrogate metal that can be measured by your CEMS (such as iron) you must 

test the CEMS at three different concentration levels. These three levels must 

incorporate at least a two-fold change in concentration and one of the levels 

must be between 80 and 120 percent of the emission limit (the concentration of 

the emission limit for the surrogate metal is equal to that for the metal measured 

by your CEMS with the highest emission limit). You are required to obtain at 

least three measurements at each concentration level and are required to have a 

total of at least 12 measurements. You must report the results of all 

measurements. The relative bias is an indicator of accuracy and should be 

calculated using equation 5 for each element. Also, the percent relative 

standard deviation, which is an indicator of precision, should be calculated for 

each metal 

If you challenge the entire CEMS system and you do not meet the test criteria 

you may apply a correction factor to your CEMS data. Calculate a correction 

factor for each metal in the relative bias test according to the equation found in 

section 4.2.13. If you challenge the sampling and XRF modules separately 

from the sample interface you may not apply a correction factor to the data 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 10 of 30 
from the relative bias test, you may, however, apply a correction factor to the 

results of the transport efficiency test. For the metal that was spiked over

several concentrations you must perform linear least squares regression analysis 

on the data. The correlation coefficient for this fit must be better than 0.90. 

This is to demonstrate that the instrument response is valid over its applicable 

range. If the criteria for this test is met then the correction factors are assumed 

to be valid over the range of the instrument. 

Option C

In accuracy test option C the entire CEMS is subjected to a relative bias test. 

The options for metals generation and the associated spiking and reference 

method requirements are the same as those for Option A under the linearity 

tests. 

Option D

In accuracy test option D only the XRF and sampling modules are subjected to 

a relative bias test. The options for metals generation and their associated 

spiking and reference method requirements are the same as those for Option B. 

You are also required to perform a transport efficiency test. 

3.1.5 Transport Efficiency Test 

You must perform a transport efficiency test if you have only challenged the sampling 

and XRF modules during the accuracy tests (options B and D). Any one of the four 

methods described below are valid ways of determining percent transport for your 

multi-metals CEMS. 

• Particulate Matter (PM): In this approach particulate matter is measured 

concurrently in two locations, (1) in the stack effluent stream as close as 

possible to your multi-metals CEMS sample interface, and (2) at a point in the 

transport system as close as possible to the sampling module. You may use any 

standard reference method to measure PM including Method 5, Method 5i, or 

Method 17 (40 CFR 60, Appendix A)iii,iv,v

. Particulate matter must be 

generated by operating the source. You must acquire at least 12 paired 

concentration measurements (each pair consists of the measurement made as 

close as possible to the sample interface and the measurement made as close as 

possible to the sampling module. The percent transmission is calculated for 

each pair using equation 6 and the overall percent transmission is determined 

by calculating the average of all twelve runs. 

• Element of opportunity: Alternatively, transport efficiency can be determined 

using a surrogate metal such as iron or zinc that is commonly present in stack 

effluent. Method 29 (40 CFR 60, Appendix A)vi or a suitable alternative can be 

used to measure the metal concentration in the stack effluent stream as close as 

possible to the sample probe and at a point in the transport system as close as 

possible to the sampling module. Also, if your XRF multi-metals CEMS is 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 11 of 30 
capable of measuring the element of interest, you may compare the measured 

concentration on the CEMS with that measured in the stationary source using 

the reference method. Transport efficiency is calculated using equation 6. You 

are required to make at least twelve paired concentration measurements to 

determine the mean transport efficiency. 

• Non-quantitative spiking: An aerosol containing a surrogate metal or a metal 

analyte can be spiked non-quantitatively into the stack or duct gas stream or 

into the transport system as close as possible to the sampling probe. The 

concentration of the spiked metal is measured by method 29 (40 CFR 60, 

Appendix A)5

 or a suitable alternative as close as possible to the CEMS’ sample 

probe and by another Method 29 or a suitable alternative as close as possible to 

the sampling module. If you spike directly into the transport line you must 

make your upstream concentration measurement as close as possible to the 

spike location and your downstream measurement as close as possible to the 

sampling module. If your XRF multi-metals CEMS is capable of measuring the 

spiked metal, you may compare its reported concentration with the in source 

metals measurement or with the upstream in transport line measurement to 

calculate transport efficiency according to equation 6. You are required to 

make at least twelve paired concentration measurements to determine the mean 

transport efficiency. 

• Quantitative Spiking: An aerosol containing a surrogate metal or a metal 

analyte can be spiked quantitatively into the stack or duct gas stream or into the 

transport system as close as possible to the sampling probe. The concentration 

may be measured on the CEMS or by using method 29 or a suitable alternative 

as close as possible to the sampling module. This measurement is then 

compared with the known concentration of the spiked aerosol to determine the 

percent transport. 

3.1.6 Dual Train Requirements 

If you use a reference method (eg., method 29 or 5i) during the linearity, relative bias, 

or transport efficiency tests it is recommended that you use dual trains to screen the 

reference method for bias and imprecision. 

3.1.7 Cycle Time Requirements 

The cycle time for your XRF multi-metals CEMS should be no greater than one-third 

of the averaging period for the applicable standard. During all phases of the 

performance specification test including the CEMS must use the same cycle time as 

will be used during day to day operation. 

3.2 How do I report the results of the initial performance specification test? 

Summarize the results of the calibration drift and accuracy tests in tabular form. Include all 

data sheets, calculations, and records of CEMS measurements necessary to substantiate the 

performance of the CEMS and any other devices or methods (e.g., method 29). The CEMS 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 12 of 30 
measurements shall be reported to the agency in units of μg/m3 on a dry basis, corrected to 

20°C. 

4.0 Performance Criteria and Calculations 

4.1 What are the performance criteria for my XRF multi-metals CEMS? 

You must demonstrate that your XRF multi-metal CEMS has adequate stability, precision, 

accuracy, cycle time and data reporting capabilities to determine if your facility is in 

compliance with metal emission standards or operating permit limits as specified in 

applicable regulations or permits. You will demonstrate this capacity by showing that your 

XRF multi-metal CEMS meets the following performance criteria. 

4.1.1 7-day Drift Check Criteria – Stability 

Upscale Drift: The upscale drift as calculated in section 4.2.8 must be less than 15% of 

the original calibration value of the upscale reference each day for seven consecutive 

days.

Zero Drift: The zero drift as calculated in Section 4.2.9 must be less than 20% of the 

emission limit each day for seven consecutive days. 

Volume or Flow Drift: The volume or flow drift as calculated in Section 4.2.11 must 

be less then 20% of the full scale value of the flow or volume measurement device each 

day for seven consecutive days. 

4.1.2 X-Ray Fluorescence Calibration Drift Criteria 

For each metal measured by your multi-metal CEMS for compliance purposes the xray fluorescence calibration drift must be less than 10% of the value of the standard. 

(Note: you are not required to calculate the XRF calibration drift for those metals used 

during the bias and precision testing). 

4.1.3 Relative Bias Criteria – Accuracy and Precision 

The relative bias of the instrument must be less than 15% and the relative percent 

standard deviation (RSD) must be 10% or less if you challenge the XRF and sampling 

modules of your CEMS separately from your transport system. If you challenge your 

entire CEMS and it does not meet the above relative bias criteria you must apply a 

correction factor to the results reported by your CEMS. The correction factor is 

calculated using the equation in section 14.2.13. Also, the correlation coefficient for a 

least squares linear regression fit of the metal that was spiked at three different 

concentration levels must be greater than 0.90. This is to help assure that the 

correction factor is applicable over the range of the instrument. 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 13 of 30 
4.1.4 Linearity Test Criteria – Accuracy and Precision 

If you choose to do linearity tests to determine the accuracy and precision of your XRF 

multi-metals CEMS the slope of the least squares linear fit should be between 0.85 and 

1.15. The correlation coefficient must be 0.90 or better and the intercept should be less 

than 20% of the applicable emission limit. If you challenge only the XRF module and 

the sampling module of your CEMS you must meet the above criteria. If you 

challenge your entire CEMS and you do not meet the slope or intercept criteria you 

must adjust the results reported by your CEMS, you must however, still meet the 

correlation coefficient criteria. The correction factor is calculated according to the 

procedures in section 4.2.12. 

4.1.5 Transport efficiency – Accuracy 

If the average transport efficiency is between 90 and 110 percent, then no correction 

for transport efficiency needs to be applied to concentrations reported by your XRF 

multi-metals CEMS. If, however, your average transport efficiency is less than 90 

percent or more than 110 percent then you must use a correction factor. You may use 

your transmission efficiency test data to establish a correction factor that would change 

the reported CEMS concentrations for each metal to a value that would reflect 100% 

transmission efficiency. 

4.1.6 Cycle time – Appropriate Reporting 

The cycle time for your XRF multi-metals CEMS must be no greater than one-third of 

the averaging period for the applicable standard.

4.2 What calculations, equations, and data analyses are needed? 

4.2.1 Arithmetic Mean 

Calculate the arithmetic mean of a data set as follows. 

= ∑ i x

n

x

1 Equation 1 

Where : 

x = Arithmetic mean 

n = Number of data points 

xi = Value of each data point 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 14 of 30 
4.2.2 Arithmetic Mean of Difference 

To calculate the arithmetic mean of difference use the above equation substitute d for x. 

Where 

CEMS RM

CEMS

RM

i i di = C − R Equation 2 

 Where: 

= The concentration of the i Ci

th element as reported by the CEMS 

Ri = The concentration of the ith element as reported by the reference 

method or aresol 

4.2.3 Standard Deviation (of differences)

1

1 2 2

−

∑ ∑ −

=

⎟

⎠

⎞ ⎜

⎝

⎛

n

d

n

d

SD

i i

i

 

Equation 3 

Where: 

SDi = The standard deviation of differences for the ith element 

n = The number of data points 

di = The difference between the concentration measured by the 

reference method or the concentration of the reference aerosol and the 

concentration reported by the CEMS. 

4.2.4 Percent relative standard deviation 

= ×100

RM

i

i

i

R

PRSD SD Equation 4 

Where: 

RM Ri = The average of the reference method data set or the reference 

aerosol concentration for the ith element 

PRSDi = The relative percent standard deviation for the ith metal 

4.2.5 Relative Bias 

= ×100

RM

i

i

i

R

d

PRB Equation 5 

Specifications for XRF Based Multi-Metals CEMS (PS-YY) Page 15 of 30 
Where d i is the mean difference, is the average of the reference method 

data set or the average aerosol concentration for the i

RM Ri

th element, and PRBi is 

the relative bias for the ith element 

4.2.6 Percent Transmission 

= ×100 S

i

i

i C

C PT

sm

 Equation 6 

Where: 

S Ci = Concentration of the ith element at the stack 

sm Ci = Concentration of the ith element at the sampling module or as 

reported by the XRF multi-metals CEMS. 

PTi = The percent transport of the ith element 

Report the average percent transport ( PT ) of all measurements for each 

element that was tested (only one element is required though more can be 

tested). 

4.2.7 Best Fit Line for Linearity Test 

Calculate the linear correlation equation given below. 

yˆ = b + b x o 1 Equation 7 

Where: 

bo = The y intercept 

b1 = The slope 

The intercept is calculated according to the following equation. 

b = y − b x o 1 Equation 8 

Where: 

∑=

=

n

i

i x

n

x

1

1 

∑=

=

n

i

i y

n

y

1

1 

The slope of the line is calculated according to equation below. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 16 of 30 
∑

∑

=

=

−

− −

= n

i 1

2

i

i 1

i i

1

( x x )

( x x )( y y )

b

n

 Equation 9 

The linear correlation coefficient is calculated according to the following equation. 

∑ ∑

∑

= =

=

− −

− −

= n

i

i

n

i

i

i

i i

x x y y

x x y y

r

1

2

1

2

1

( ) ( )

( )( )

n

 Equation 10 

4.2.8 Upscale Drift 

×100 − = u

i

i i

i L

L L

UD

cemu u

 

Equation 11 

Where: 

UDi = The upscale drift of the ith element on your CEMS in percent. 

cemu Li = The measured CEMS response to the ith element in the upscale 

standard 

u Li = The calibrated value of the ith element of the upscale standard 

4.2.9 Zero Drift 

×100 − = L

i

i i

i C

L L

ZD

cemo 0

 

Equation 12 

ZDi = The zero drift of the ith element on your CEMS in percent 

cemo Li = The measured CEMS response to the zero standard for the ith

element 

0 Li = The calibrated value of the ith element on the zero standard 

L Ci = The emission limit of the ith element 

4.2.10 X-Ray Fluorescence Calibration Accuracy 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 17 of 30 
×100 − = std

i

std

i

cem

i

i L

L L

CA

 Equation 13 

Where: 

CAi = X-ray fluorescence calibration accuracy 

= The value of the standard reported by your CEMS cem Li

std Li = The known value of the standard 

4.2.11 Daily Sample Volume Check 

×100 − = FS

V V

VD cemr m Equation 14

Where: 

VD = Volume drift 

Vcemr = Sample gas volume (or flow) measured by the CEMS volume 

check measurement device 

Vm = Sample gas volume (or flow) reported by your multi-metal CEMS 

FS = Full scale value of the CEMS volume (or flow) measurement 

device 

4.2.12 Linearity Test Correction Factors (Applicable only when the linearity test 

challenges the entire CEMS)

1. Correction equation if CEMS does not meet either the slope or the intercept 

criteria. 

1

0

b

y b CC i

i

− = 

 

Equation 15 

Where:

 = corrected CEMS concentration for the i C Ci

th element 

yi = CEMS reported concentration for the ith element 

b0 = the intercept of the least squares linear regression line 

b1 = the slope of the least squares linear regression line 

2. Correction factor if CEMS meets intercept criteria, but does not meet the 

slope criteria.

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 18 of 30 
 

1 b

y CC i

i = 

 

Equation 16 

3. Correction factor if CEMS meets slope criteria but does not meet intercept 

criteria.

 

b0 C yi

C

i = − Equation 17 

4.2.13 Relative Bias Correction Factors 

CEM

i

RM

i

RM

i

i

RB

i

C

R

R

d

CF =

+

=

1

1 Equation 18 

 

Where: 

RB CFi = The relative bias correction factor for the ith element 

CEM Ci = The average reported concentration of the CEMS for the ith

element 

RM Ri = The average of the reference method measurements for the ith

metal 

4.2.14 Percent transport correction factor

i

PT

i

PT

CF 1 = Equation 19

Where 

PT CFi = Correction factor for percent transport for the ith element 

PT i = Average percent transport for the ith element 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 19 of 30 
5.0 Other Requirements and Information 

5.1 What quality control measures are required? 

Quality control measures for an XRF multi-metal CEMS are addressed in procedure Z 

“Quality Assurance Requirements for X-Ray Fluorescence Based Multi-Metals Continuous 

Emission Monitors.” 

5.2 What calibration and standardization procedures must I perform? 

Refer to your CEMS owner’s manual and manufacturer to determine what calibration and 

standardization procedures are required for your multi-metal CEMS. 

5.3 What pollution prevention procedures must I follow? [reserved]

5.4 What waste management procedures must I use? 

All chemicals used to produce a reference aerosol or in performing standard methods need to 

be disposed of properly. 

5.5 What reference tables and figures are relevant to PS-YY? 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 20 of 30 
Table 1. Initial Performance Specification Tests and Criteria 

Test 

Category 

Test Test Requirements Test Criteria 

Zero Drift Monitor zero standard for 7 

consecutive days under normal 

operating conditions 

< 20% drift every day for seven 

consecutive days

Upscale Drift Monitor upscale standard for 7 

consecutive days under normal 

operating conditions 

< 15% drift every day for seven 

consecutive days Seven Day 

Stability 

Flow Drift Monitor flow drift for 7 consecutive 

days under normal operating 

conditions 

< 20% drift every day for seven 

consecutive days

Calibration

X-Ray Fluorescence 

Calibration Drift Check

Test a standard for each element 

measured for compliance by your

CEMS 3 times 

< 10% drift for every element

measured for compliance by

your CEMS 

Option A

Perform a linearity test on 

entire CEMS

• At least one metal from each

category 

• Need at least 3 concentration

levels which include a 2 fold 

conc. change and the emission 

limit 

• If spiking, spike into source, or 

spike into transport line as close 

as possible to the probe 

• Slope = 0.85 to 1.15 

• r > 0.90 

• intercept < 20% of emission 

limit 

• if the above criteria are met 

then no correction 

• if not met apply a correction 

(correlation criteria must be

met)

Option B

• Perform a linearity test

on sampling module 

and XRF module only

• Determine transport 

efficiency separately

• At least one metal from each

category 

• Need at least 3 concentration

levels which include a 2 fold 

conc. change and the emission 

limit 

• Spike or measure concentrations

with reference method as close as 

possible to the sampling module 

Linearity Criteria

• Slope = 0.85 to 1.15 

• r > 0.90 

• intercept < 20% of emission 

limit 

• the linearity criteria must be 

met

Percent Transport Criteria

• 90<PT<110 

• If percent transport criteria

are not met apply a 

correction factor

Option C

Perform a relative bias test 

on entire CEMS 

• At least one metal from each

category at 80 to 120 percent of

emission limit 

• One other metal at 3 conc. levels 

which include a 2 fold conc. 

change and the emission limit 

• If spiking, spike into source or

spike into transport line as close 

as possible to the probe 

Percent relative Bias

RB< 15% 

%RSD < 10% 

r > 0.90 for metal with three 

fold conc. change

• If Criteria not met apply a 

correction factor (correlation 

coefficient criteria must be

met)

Accuracy 

Option D

• Perform a relative bias 

test on sampling 

module and XRF 

module only

• Determine transport 

efficiency separately

• At least one metal from each

category at 80 to 120 percent of

emission limit 

• One other metal at 3 conc. levels 

which include a 2 fold conc. 

change and the emission limit 

• Spike or measure concentrations

with reference method as close as 

possible to the sampling module 

Percent Relative Bias Criteria

RB< 15% 

%RSD < 10% 

r > 0.90 for metal with three 

fold conc. change

Percent Transport Criteria

• 90<PT<110 

• If percent transport criteria

are not met apply a 

correction factor

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 21 of 30 
Figure 1: Types of metals generation available for accuracy tests. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 22 of 30 
Figure 2: Flow chart for using quantitative spiking during the accuracy tests. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 23 of 30 
Figure 3: Flow chart for using non-quantitative spiking during the accuracy tests.

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 24 of 30 
Figure 4: Flow chart for using stack operation to generate metals concentrations. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 25 of 30 
Figure 5: Species available for transport tests 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 26 of 30 
Figure 6: Procedure for percent transport using PM. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 27 of 30 
Figure 7: Procedure for percent transport determination using an element of 

opportunity. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 28 of 30 
Figure 8: Procedure of percent transport determination using spiking.

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 29 of 30 
5.6 What references apply to PS-YY? 

i. United States. Environmental Protection Agency [EPA]. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 1: Sample

and Velocity Traverses for Stationary Sources. Washington, DC: EPA; 2004. 

Available: http://www.epa.gov/ttn/emc/promgate/m-01.pdf via the Internet. Accessed 

May 8, 2005. 

ii United States. Environmental Protection Agency [EPA}. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 2: 

Determination of Stack Gas Velocity and Volumetric Flow Rate. Washington, D.C: 

EPA; 2004. Available: http://www.epa.gov/ttn/emc/promgate/m-02.pdf via the 

Internet Accessed May 10, 2005.

iii. United States. Environmental Protection Agency [EPA]. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 5: 

Determination of Particulate Matter Emissions from Stationary Sources. Washington, 

DC: EPA; 2004. Available: http://www.epa.gov/ttn/emc/promgate/m-05.pdf via the 

Internet. Accessed May 10, 2005. 

iv. United States. Environmental Protection Agency [EPA]. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 5i: 

Determination of Low Level Particulate Matter Emissions from Stationary Sources. 

Washington, DC: EPA; 2004. Available: http://www.epa.gov/hwcmact/frhwc5.pdf via 

the Internet. Accessed May 10, 2005. 

v. United States. Environmental Protection Agency [EPA]. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 17: 

Determination of Particulate Matter Emissions from Stationary Sources. Washington, 

DC: EPA; 2004. Available: http://www.epa.gov/ttn/emc/promgate/m-17.pdf via the 

Internet. Accessed May 10, 2005.

vi. United States. Environmental Protection Agency [EPA]. Technology Transfer 

Network. Emission Measurement Center. Promulgated Methods. Method 29. 

Determination of Metals Emissions from Stationary Sources. Washington, DC: EPA;

2004. Available: http://www.epa.gov/ttn/emc/promgate/m-29.pdf via the Internet. 

Accessed May 18, 2005. 

Specifications for XRF Multi-Metals CEMS (PS-YY) Page 30 of 30