MEMORANDUM:

DATE: June 5, 2014

SUBJECT: Determination of “non-detect” from EPA Method 29 (multi-metals) and EPA Method 23 

(dioxin/furan) test data when evaluating the setting of MACT floors versus establishing

work practice standards.

FROM: Steffan Johnson

Measurement Policy Group, SPPD

TO: SPPD Rule Writers, SPPD Policy and Strategies Group, SPPD Measurement Policy Group, 

AQAD Measurement Technology Group, and SPPD management.

1. Background

Maximum Achievable Control Technology (MACT) floor development at EPA has highlighted the need for 

more consistent understanding of detection limits from EPA emission testing methods and how they are 

applied to the rule making process. Detection limits are used both as baseline emission values where 

below detection limit values are reported and for determination on whether to pursue a MACT floor or a 

work practice standard. When a pre-determined majority of emissions test results demonstrate that

the pollutant of interest is not generally present in measurable quantities a work practice is typically 

written. The exception being that work practice standards do not apply for CAA Section 129 rules. 

This guidance memo is focused on the use of detection limits as an indicator of the measurable presence 

of a given pollutant, specifically where multi-component samples of metals or dioxin/furan emissions 

are the pollutants of concern. For multicomponent measurement methods there are several variations 

to the detection limit issue that have not been addressed in guidance already developed for the use of 

detection limits in setting standards. Currently, these variations lack clarity on the criteria used to 

determine what constitutes a “non-detect” for any particular set of these multi-component test method

data. Lacking the further refinement provided by this memo, “non-detection” variations for 

multicomponent methods may currently be defined as any of the following:

a) A majority of the metals or dioxin/furan congeners being non-detect.

b) Any single metal or dioxin/furan congener reported below detection.

c) Absence of any measurable amount of every metal or congener.

d) A non-detect in any one portion of a sample train. 

A reasoned and consistent approach to making this determination is necessary so that we put forth rule 

requirements that are scientifically sensible, consistent, appropriate, and defensible. 
Caveats:

Understanding terminology and context is paramount to evaluating detection limits. A December 13, 

2011 memo from Peter Westlin and Ray Merrill (EPA Docket item EPA-HQ-OAR-2011-0817-0142) titled 

“Data and procedure for handling below detection level data in analyzing various pollutant emissions 

databases for MACT and RTR emissions limits” provides guidance on what Representative Detection 

Limits may be expected from the analysis of multi-metals (Method 29) and dioxin/furan (Method 23) 

test results. This memorandum refers to RDLs (Representative Detection Limits) and these will be our 

primary grounding rod for making decisions regarding use of metals data. EDL (Estimated Detection 

Limit) values for dioxin/furan lab results will be our benchmark for reviewing dioxin/furan test data. As 

the Westlin/Merrill memo is referenced several times in this document it serves you, the reader, well to 

read and understand the memo thoroughly. This document contains some screenshots from the 

Westlin/Merrill memo to enhance your understanding of the process and the overall context of the 

discussion and how it relates to that memo. 

RDL is an EPA-derived term, and the RDLs in the Westlin/Merrill memo were determined by averaging 

the lowest MDL (Method Detection Limit) data submitted for individual tests during the Utility (MATS) 

NESHAP ICR and the Industrial Boiler NESHAP Rule ICR. The MDL is a key indicator and it is critical that 

these individual test and laboratory determined values are determined consistently by each laboratory. 

The MDL should also be identified in each test/lab report. ICR test requirements now include the 

reporting of the lab’s MDL with their data sets, even though the reporting of MDL is not a current 

requirement of many EPA air compliance test methods. MDLs are often inconsistently reported in 

emission test reports or associated lab data, and some other “quantification value” or “reporting limit” 

value (RL, PQL, QL, etc.) is often substituted by the lab. Rule writers and their contractors must be 

vigilant to be sure and use an appropriate MDL and RDL value when evaluating detection limits; the 

Westlin/Merrill RDL table value is a tool well-suited for that purpose. It is important to know that a lab’s 

“reporting limit” (or PQL, QL, etc.) is not necessarily the MDL we are looking for, especially if they are 

much higher than the RDLs in the Westlin/Merrill memorandum. Where this is the case such values are 

very likely in the RL/PQL/QL, etc., pool and should not be used as one would use an MDL. With 

dioxin/furan test results, EDL is an appropriate benchmark to use and EDL data are those referenced on 

page 8 of the Westlin/Merrill memo.

Definitions: 

ADL (Above Detection Limit): Results from the lab show measured values above the MDL. (Be 

sure to distinguish reported values as being above the MDL versus above the RL or other lab 

‘confidence’ level). 

BDL (Below Detection Limit): A laboratory result where detectable amounts of an individual 

pollutant or congener are not found. Again, evaluate the data to ensure BDL means “below MDL” and 

not “below RL” or some other ‘confidence’ level.
DLL (Detection Limit Limited): A test result where some fractions of the analysis return 

detectable amounts of a pollutant or congener (above MDL), while other fractions are BDL.

EDL (Estimated Detection Limit): For Dioxin/Furan tests, a commonly reported estimate of the 

concentration where a given analyte would have to be present to produce a signal with a peak height of 

at least 2.5x the background noise signal level. The EDL determination is done for each sample set at 

the time of analysis. This is specific to the analytical technique and is affected by factors such as sample 

size, dilution, etc., commonly reported for non-detected analytes instead of other values such as PQL, 

RL, QL, etc. It is important to note that EDL and MDL are not the same, but EDL is a standard benchmark 

for determining detection from an isotope dilution analysis, common to dioxin/furan emission testing.

EMPC (Estimated Maximum Potential Concentration): for Dioxin/Furan analysis, a congener 

value reported by a lab that is meant to flag some uncertainty in the quantitation of the reported value, 

specifically when the signal-to-noise ratio is at least 2.5 or higher for both quantitation ions but the ion 

abundance ratio criteria are not met. In general, EMPC data are considered to be actual emissions until 

shown otherwise. EMPC values may be below, at, or above the MDL for that congener, and may involve 

some other analytical interference (or not). EMPC values below the MDL for any congener are treated 

as BDL for the purposes of this exercise. EMPC values at or above the MDL for any congener must be 

treated as measured values.

LOQ (Level of Quantitation): A value where measurement certainty increases to 95%, generally 

equivalent to a value ranging from 3x – 5x the MDL.

MDL (Method Detection Limit): Synonymous with the term LOD (Level of Detection) the MDL is 

defined as the lowest quantity of a substance that can be distinguished from the absence of that 

substance (i.e. a blank value) with a stated level of confidence. For the purposes of this document, the 

process of identifying the MDL of a given substance is defined in EPA Method 301, Section 15.

PQL (Practical Quantitation Limit): Synonymous with the term LOQ (Level of Quantitation).

QL (Quantification limit): A term that is loosely used, sometimes synonymous with MDL, and 

other times synonymous with RL or PQL. As such, a reported QL requires extra scrutiny during report 

review to ascertain the context of its usage.

RDL (Representative Detection Limit): Sometimes referred to as the Representative Method 

Detection Limit (RMDL) this is the mean MDL value of a specific analyte determined by an MTG review 

of l lab analyses represented by labs who provided data for best performing sources, thereby creating a 

representative value by which to assess detection such that the best performing lab handing any 

particular analytical sample does not drive all detection limit discussion and decision making. By 

establishing this value as the mean of several labs we allow for the selection of local and cost effective 

analysis of environmental samples while maintaining a balance of quality analyses. The Westlin/Merrill 

memo defines RDL for dioxin/furans as EDL x 2.
RL (Reporting Limit): A value determined by an analytical laboratory to represent the lowest 

concentration of an analyte that they are certain they can accurately quantify. This can be some 

multiple of the MDL or may just be the lowest calibration standard for the Laboratory’s standard 

analysis method. Many labs report this value instead of the MDL.

2. Discussion

Drivers:

The Westlin/Merrill memorandum provides specific guidance on the determination of a representative

method detection limit and the use of that value in determination of a MACT floor limit, but setting 

MACT floor limits is not the only time a rule writer will find detection limit information useful.

Detection limit evaluation is also important to EPA rule writers when determining whether to develop a 

MACT floor limit or, where emissions of a particular pollutant are not demonstrated to exist in 

measurable quantities, to develop work practice standards for management of emissions potential. The 

Office of General Council (OGC) has provided SPPD rule writers some guidance on what percentage of 

data in a data set may be necessary to meet their expectation of when a work practice standard is 

appropriate. At the time of this writing, OGC’s guidance states that at least 55% of the test data, 

including those outside the group of best performing sources, must be non-detect in order to justify a 

work practice standard (versus setting a limit). Even with this clear statement from OGC on this policy, 

there is a need for a consistent approach concerning multi-component samples to resolve current

ambiguity on how to balance the four types of non-detect data for pollutants such as metals and 

dioxins/furans.

In the previous guidance it was clear with a single component test, such as an HCl emissions 

measurement, the rule writer only needs to evaluate the number of test results that are below the 

detection limit in relation to the number of test results available and determine the direct percentage of 

non-detect values; this is straightforward enough. The assessment is more complex with a multicomponent sample, such as a Method 29 multi-metals test result. Lab analysis from this test can return 

information on up to on sixteen non-mercury metals. Each metal analysis may have two separate 

fractions: front-half (filter) and back-half (impinger catch). Each fraction is analyzed separately at the lab 

and thus has a separate detection limit, and each metal may have detection from one, both, or neither 

fraction. There may be emission sources where a few metals dominate the emissions and the majority 

of the remaining metals are nearly absent. With three test runs per pollutant, and 2 analytical fractions 

each having its own detection limit, and sixteen analytes being sampled, there are 96 sample fractions 

potentially represented in the data set. What then constitutes “non-detect” in regards to the individual 

metals tests, much less the combined results of all the metals analyses? This assessment complexity 

increases with Dioxin/Furan emission tests as a result of calculating a Toxic Equivalents (TEQ) which 

multiplies different components by a weighting factor and sums the components to yield a single value 

that is applied as an aid to assessment.
In review of non-mercury multi-metals data:

EPA Method 29 is capable of measuring 17 metals, including mercury, with repeatable accuracy and 

precision. The method uses isokinetic sampling with a filter to separate out particulate matter 

(including particle bound metals) and acidic absorbing solution behind the filter to oxidize and capture 

non-mercury metals that may be present in vapor forms. When reviewing Method 29 data one must 

keep in mind that some metals may be present only in a single form (all particulate or all vaporous) or in 

both particulate and vaporous forms, in varying ratios. It is also important to understand that while 

Method 29 has a single sampling technique the tester has the option of asking the lab to determine the 

metal concentrations by one of four different analytical approaches(except for mercury which has a 

single analytical technique). The analytical approach chosen for the sample makes a difference, 

especially in terms of the method’s ability to achieve low detection. These four analytical approaches 

are:

I. Atomic Absorption Spectroscopy (AAS)

II. Inductively Coupled-Atomic Emission Spectroscopy (ICP-AES)

III. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

IV. Graphite Furnace Atomic Absorption Analysis (GFAAS)

It is not critical for the reader to understand the intricacies of each of these analytical techniques, but it 

is important to understand that the first two on the list will result in generally higher detection limits 

from any given lab than the last two will. While this is not true for some of the common metal analytes 

which are present at relatively high concentration, it is true for the majority. For this reason we have 

started requiring one of the latter two analytical techniques when asking for Method 29 data in recent 

ICRs.

It is also essential to understand that laboratories often, though not always, report two analytical 

fractions for each metal; one representing the front half (filterable) and one representing the back half 

(vaporous) results. This reporting variability originates from the option in Method 29 to allow a single 

analytical fraction (it is easier to achieve detection when the entire sample is rolled into a single 

analytical fraction). For this reason the Westlin/Merrill memorandum lists a single RDL for each metal, 

and provides guidance for what that RDL value may be if the sample volume is increased. It is 

appropriate to sum the MDL for both halves (when two fractions are reported) for comparison to the

RDL in the Westlin/Merrill memorandum, as that document is based on the combined MDL (see 

reference image 4-1). Where a lab report provides a “reporting limit” or “practical quantitation limit”

(see above definitions) the sum of these two fractions is likely to differ greatly from the RDL listed in the 

Westlin/Merrill memo. Where a lab reports an MDL, the sum should be very close (maybe lower, 

maybe higher) to the listed RDL for a 1 dscm sample volume.

A single metal analyte reported in excess of the MDL listed for the appropriate analytical fraction of 

Method 29 signifies “detection” of that analyte. Note that this may include DLL data points as one 

fraction may show high detection while another fraction of the same sample is below the detection 

limit. 
Method 29 detection, as we discuss it in this memo, should be determined on a per-analyte basis.

Therefore with any given test run, if any individual metal is detected, there is detection for that metal in 

that test result. Detection versus non-detection must not be based on the entire group of metals; but 

rather they must be treated individually and on a run-by-run basis, though consideration for MACT floor 

development or work standard development will be made by considering the pool of test run results.

In review of dioxin/furan data:

EPA Method 23 measures 10 furan congeners and 7 dioxin congeners, for a total of seventeen reported 

congeners. Dioxin and furan sampling is unlike metals testing in that they are not a class of compounds 

containing a unique periodic element with an established toxicity but rather individual compounds 

(congeners) that are representative of a class of compounds with varying degrees of toxicity. Another 

distinguishing difference is that dioxin/furan measurements are reported in units of picograms, making 

them at least a thousand times less concentrated in samples than metals; mercury for example. The 

detected congener mass, corrected to 7% oxygen concentration is typically used in regulatory limits as

the sum of all the individual compounds or as a toxicity weighted sum of those compounds. Method 23 

includes procedures for developing an Estimated Detection Limit (EDL) and this memo uses the data 

derived from that procedure for decision making.

To aid in the understanding of the health impact of dioxin/furans with their small concentration and

widely varying toxicity, the World Health Organization developed and EPA has adopted a “Toxic 

Equivalency Factor” (TEF) multiplier for each dioxin/furan congener. By making use of the TEF 

multipliers to produce the toxicity weighted sum and the resulting single value Toxic Equivalency (TEQ),

emissions, we can make an informed decision about the detection level of the compiled group of 

congeners. Some important points of TEF’s and TEQ’s are:

 Toxic equivalency factor (TEF) expresses the toxicity in terms of the most toxic dioxin, 2,3,7,8-

TCDD

 Toxic equivalency (TEQ) expresses the toxicity-weighted masses of D/Fs: TEQ = ∑[Ci]*TEFi, 

Where: Ci is the concentration of individual compounds and TEFi is the toxic equivalency factor 

for that individual compound.

Page 8 of the Westlin/Merrill memorandum contains an example spreadsheet (see Reference Image 4-

2) that displays each congener and an RDL for mass of that congener in nanograms, as well as the 

equivalent TEQ for that congener at that mass. The Toxic Equivalency Factor (TEF) is a value used for 

developing the TEQ amounts. The TEF values are based on the values for mammals from the World 

Health Organization 2006 tables located on page 13 of this report: http://www.epa.gov/raf/files/tefsfor-dioxin-epa-00-r-10-005-final.pdf. When and where more recent World Health Organization (WHO)

mammalian values are available, those would be deemed more appropriate for this purpose. The 

Westlin/Merrill memo discuses RDL as (EDL x 2), and the EDL values are those listed in the table on page 
8 of the memo, whereas the line third from the bottom labeled “sum” is the sum of EDL values; or the 

overall method EDL.

For MACT calculations, when determining detection versus non-detection, for a Method 23 data set the

steps are as follows:

1. Ensure that the D/F data are reported in terms of nanograms. If the data are reported in 

some other mass unit, you will need to convert them to nanograms. If you have values that 

are corrected to 7% oxygen look through the test report to find the uncorrected mass 

values.

2. Ascertain that the correct WHO TEF factors (outlined above) were used to generate a 

congener specific TEQ. If only D/F mass was reported, the TEQ value must be calculated 

from these factors.

3. Where a lab reports EMPC (Estimated Maximum Potential Concentration) values, use care 

to make certain that these are reported as dioxin/furan emissions. EMPC values below the 

corresponding congener specific EDL (estimated detection limit) value from the 

Westlin/Merrill memo are counted as BDL for the purposes of this evaluation.

4. Sum the TEQ values of all detected (ADL) values from the test run (include EMPC values 

above EDL values). If an individual congener is listed as non-detect or otherwise reported 

below the corresponding EDL of the Westlin/Merrill memo, use the value of zero to 

represent that congener in this summation.1

5. Next, compare that sum to the Sum TEQ value (sum of EDL’s as TEQ) in the table on the final 

page of the Westlin/Merrill memo (this value is currently listed as 4.11E-02 for Industrial 

Boilers/CISWI and 1.8E-02 for all other sectors, but be sure to use the most recent version of 

the memo as the December 2011 version is expected to change in the future). 

6. If the sum of the TEQ from the detected congeners is at or above the sum of congener TEQ 

values from the Westlin/Merrill memo, there is detection of dioxin/furans in that sample. If 

the sum of the TEQ from the detected congeners is below the sum of congener TEQ value in 

the Westlin/Merrill memo, the test run is considered to be non-detect for dioxin/furan.

7. The data may now be used in the decisions about whether to set a work practice standard 

versus an emission limit for dioxin/furans. (See examples later in this memo). 

NOTE: Of particular interest is the table on page 4 of the Westlin/Merrill memorandum that lists one 

Method 23 RDL for D/F congeners for industrial boilers and another RDL for utility boilers and all other 

sources. The memorandum states on page 3 why this is the case and prescribes that it is the RDL 

developed from utility boiler data that is most representative of achievable detection limits, so we point 

to that value as our benchmark for sources other than Industrial Boilers. As of this writing, AQAD/MTG 

is looking into development of a non-sector based RDL for dioxin/furan, and this procedure is expected 

 

1 While BDL congeners may be considered as zero for the purposes of this memo it is important to understand that 

some test methods and ICR’s will request that these same values be reported at the EDL value, even if they are 

BDL, and different TEQ values would be calculated in those instances.
to be revised to incorporate those non-sector based RDLs after they are published and will be updated, 

as necessary, at that later date.

Dioxin/furan detection, as we discuss it in this memo, should be determined as the TEQ sum (sum of EDL 

as TEQ) of detected congeners. EDL for each congener is defined by the equation in section 9.8 of 

Method 23.

3. Detection Limit Versus Work Practice Determination

The following procedures will be used when making a determination of “Detection” from multi analyte 

samples, specifically multi-metals tests and dioxin/furan tests:

Mercury and non-mercury metals from EPA Method 29:

1. Method 29 should be evaluated on an analyte by analyte basis.

2. Care must be taken to use the correct chart for RDL comparison (pages 5-6 of Westlin/Merrill 

memo), based on the analytical method used by the laboratory.

3. Where test results for any single analyte are detection level limited (DLL) or above detection 

level (ADL), we assume detection for that test run data, for that specific analyte. See example 1 

below.

4. If an analyte is below detection level (reported as BDL) (no fraction DLL or ADL) and the reported 

detection level is at or below the Westlin/Merrill noted RDL (not the 3x RDL value), the test run 

result is below detection for that analyte. See example 2 below.

5. If an analyte is reported as BDL and the reported MDL detection level is above the 

Westlin/Merrill noted RDL (not the 3x RDL value) the test result is said to be below detection.

6. If an analyte is reported using an RL, PQL, etc. (not an MDL) and is reported as being below that 

level (not detected), the data must be set aside and not used for this purpose. See example 3 

below. (Note: Method 23, section 9.8 requires the development and reporting of an MDL).

7. The percentage criteria for determining whether to write a work practice standard or to write an 

emission limit for specific combined metal HAPs or for selected individual metals would be 

based upon the percentage of individual test runs.

Example 1: Nickel results from a test where the metals analysis was done by ICP-MS show 7.1E+00 

ug/dscm of nickel from the front half fraction of a Method 29 test, and <2.1E+00 ug/dscm from the back 

half fraction. The sum of these is 9.2E+00 micrograms/dscm which is above the listed RDL of 5.4E+00 

ug/dscm in the third table in the Westlin/Merrill memorandum (see Reference Image 4-1). Because 

nickel was detected in the front half fraction, this test run shows detection of nickel.
Example 2: Chromium results from a test where the metals analysis was done by ICP-MS show <1.2E-01 

ug/dscm of chromium from the front half fraction of a Method 29 test, and <1.2E-01 ug/dscm from the 

back half fraction. The sum of these is 2.4E-01 ug/dscm which is below the listed RDL of 3.0E-01 

ug/dscm in the third table in the Westlin/Merrill memorandum (see Reference Image 4-1). This test run 

is a non-detect for chromium.

Example 3: Chromium results from a test where the metals analysis was done by ICP-MS are reported at 

<5.2E-01 ug/dscm from the front half fraction of a Method 29 test, and < 5.2E-01 ug/dscm from the back 

half fraction. Chromium is reported at a total of <10.4E-01 ug/dscm. This result displays the use of a 

“Reporting Limit” or “Practical Quantitation Limit” or other construct used by the lab, because the 

reported “detection” values are far greater than the listed RDL (in this case 3.46 times above the RDL of 

3.0E-01). In such a case, we are not informed enough to determine if values of the analyte were 

detected between the reported value and the RDL, and so this data must be set aside and not used for 

the purposes of determining the appropriateness of setting a work practice standard. Note: This case 

applies to BDL data only. Were any fraction ADL (meaning the test run is DLL for this metal), this data 

would be appropriate to use for this purpose.

Dioxins and furans from EPA Method 23:

1. Method 23 data must be evaluated as the TEQ sum of detected congeners for each test run (see 

Reference Image 4-2).

2. EMPC values must be considered to be dioxin/furan emissions unless they are below the

congener specific EDL listed in the Westlin/Merrill memo. If a reported EMPC is greater than the

EDL, that congener is considered to be detection level limited (DLL,), not BDL. If the EMPC is 

below the EDL, then the EMPC must be considered as BDL for the purposes of this exercise.

3. All congeners reported as, or determined to be BDL must be considered as “zero” and not

included in the sum used as the decision point for this exercise.

2

4. All congeners that are above the detection limit must be multiplied by the corresponding TEFs 

from the most recent WHO (mammals) table to determine the individual congener TEQ.

5. The sum of all detected TEQ is compared to the appropriate Westlin/Merrill TEQ value: 

a. For all industry sectors other than Industrial Boilers the Utilities TEQ must be used, 

and refer to the corresponding EDL based on the Westlin/Merrill memorandum, page 4

(see Reference Image 4-3). The sum of the TEQ must fall at or below 1.8E-02 to be 

considered non-detect. 

b. For Industrial Boilers, the sum of the TEQ must fall at or below 4.11E-02 to be 

considered non-detect.

 

2 While BDL congeners may be considered as zero for the purposes of this memo it is important to understand that 

some test methods and ICR’s will request that these same values be reported at the RDL value, even if they are 

BDL, and different TEQ values would be calculated in those instances.
6. Complete this exercise for all collected data, and compare the results on a run-by-run basis. 

Decisions about whether to set a work practice standard versus an emission limit for 

dioxin/furans may now be evaluated. (See examples later in this memo). 

Example 1:

The testing of a coal fired facility yields the following Method 23 data. The results are then adjusted to 

substitute zero values for congeners with BDL values.

Congener Reported TEQ Adjusted TEQ (BDL = 0)

OCDD 2.90E-05 2.90E-05

OCDF 7.99E-06 7.99E-06

1,2,3,4,6,7,8 HpCDD <1.08E-04 0.00E+00

1,2,3,4,6,7,8 HpCDF 3.41E-04 3.41E-04

1,2,3,4,7,8 HxCDD 4.46E-04 4.46E-04

1,2,3,4,7,8 HxCDF 3.92E-03 3.92E-03

1,2,3,4,7,8,9 HpCDF <1.20E-04 0.00E+00

1,2,3,6,7,8 HxCDD <4.93E-04 0.00E+00

1,2,3,6,7,8 HxCDF 3.93E-04 3.93E-04

1,2,3,7,8 PeCDD <1.73E-02 0.00E+00

1,2,3,7,8 PeCDF 2.50E-04 2.50E-04

1,2,3,7,8,9 HxCDD <1.30E-03 0.00E+00

1,2,3,7,8,9 HxCDF 3.19E-04 3.19E-04

2,3,4,6,7,8 HxCDF 9.66E-04 9.66E-04

2,3,4,7,8 PeCDF <1.85E-03 0.00E+00

2,3,7,8-TCDD <1.34E-02 0.00E+00

2,3,7,8-TCDF 9.55E-04 9.55E-04

Sum TEQ 4.22E-02 7.63E-03

Since this data was generated from the Industrial Boiler / CISWI categories, the value we use for comparison is a 

Sum TEQ of 4.11E-02 or the current value displayed on page 4 of the most recent Westlin/Merrill memorandum 

(see Reference Image 4-3). Since 7.63E-03 is less than 4.11E-02, this test would be considered a non-detect for 

dioxin/furan.
Example 2:

A test of a brick manufacturing facility returns the following reported data. Again, the reported values are then 

adjusted to substitute zero values where BDL values were reported.

Congener Reported TEQ Adjusted TEQ (BDL = 0)

OCDD 1.29E-04 1.29E-04

OCDF 1.85E-05 1.85E-05

1,2,3,4,6,7,8 HpCDD 1.48E-04 1.48E-04

1,2,3,4,6,7,8 HpCDF 4.41E-04 4.41E-04

1,2,3,4,7,8 HxCDD <2.21E-04 0.00E+00

1,2,3,4,7,8 HxCDF <1.74E-03 0.00E+00

1,2,3,4,7,8,9 HpCDF 1.12E-03 1.12E-03

1,2,3,6,7,8 HxCDD 9.93E-04 9.93E-04

1,2,3,6,7,8 HxCDF <1.55E-04 0.00E+00

1,2,3,7,8 PeCDD 1.31E-02 1.31E-02

1,2,3,7,8 PeCDF <1.20E-04 0.00E+00

1,2,3,7,8,9 HxCDD <8.00E-04 0.00E+00

1,2,3,7,8,9 HxCDF 3.62E-04 3.62E-04

2,3,4,6,7,8 HxCDF 1.15E-03 1.15E-03

2,3,4,7,8 PeCDF 1.65E-03 1.65E-03

2,3,7,8-TCDD 1.11E-02 1.11E-02

2,3,7,8-TCDF <3.04E-04 0.00E+00

Sum TEQ 3.36E-02 3.02E-02

This test run demonstrates detection for dioxin/furan because the sum is greater than the 1.8E-02. Recall 1.8E-02 

is the Sum TEQ to be compared against for utility boilers and all other industry sectors (See Reference Image 4-3).
4. Reference Images

The following are screenshot images taken from specific pages in the Westlin/Merrill Memo and are 

included here to add clarity to the discussion and findings above. Please refer to the most recent copy of 

the Westlin/Merrill memo for actual values used in your determinations, as these values are subject to 

change with time; the screenshots below may be outdated.

Reference Image 4-1:

Reference Image 4-1 (above): RDL values for Method 29 Multi-Metals sampling taken from page 6 of the 

December 2013 Westlin/Merrill memo. Note that RDL decreases for each compound proportional to increased 

sample volume. The circled values above illustrate the ‘standard RDL’ for chromium from a 1 dscm sample volume 

(left) and the reduced RDL that could be obtained by collecting a 3 dscm sample volume (right) that is generally 

achieved by extending the test duration. It is worth noting that the lab reported MDL should be close to the 1 dscm 

value shown, no matter what sample volume was collected. Also note that this image is for ICP/MS and GFAAS 

analysis. Page 5 of the Westlin/Merrill memo outlines a different set of RDL values for ICP/AES and AA analytical 

techniques; be sure to refer to the correct table appropriate to your data set.
Reference Image 4-2:

Reference Image 4-2 (above): TEQ and EDL values taken from Page 8 of the December 2013 Westlin/Merrill 

memo and represent dioxin/furan detection limit values from Industrial Boiler testing. Note that the line labeled 

“sum” (third from the bottom) is synonymous with the term EDL and the value in the red oval is the sum TEQ value 

we use for evaluation with a dioxin/furan data set from an Industrial Boiler emission test. The RDL value (green 

rectangle) is appropriate for use when setting a MACT floor with this data set (see Reference Image 4-3), should 

your test data indicate sufficient detection. 
Reference Image 4-3:

Reference Image 4-3 (above): TEQ and Total Mass values representing data collected either from Industrial 

Boilers, or from Utilities and all other sources. This image is from Page 4 of the Westlin/Merrill memo and 

provides MACT floor setting guidance where detection is shown for a given data set; that detection decided by 

following the process described in Section 3 of this memo). Note that both the sum mass (ng) and sum TEQ are 

represented for each category; be sure to refer to the correct table appropriate to your data set. The value in the 

green rectangle correlates to the sum TEQ value indicated in Reference Image 4-2 on the previous page. The value 

in the blue diamond represents the same sum TEQ value were the data set derived from Utility boiler or other 

industrial source category test data. 

Steffan Johnson

Measurement Policy Group

Sector Policy and Programs Division

Addressees:

SPPD management

SPPD technical staff

Cc:

Group Leader, MTG, AQAD

Ray Merrill, MTG, AQAD

Kristen Benedict, MTG, AQAD

Robin Segall, MTG, AQAD

Jason DeWees, MTG, AQAD