TECHNICAL REPORT

Summary of Formaldehyde Emissions Measurement and Data 

Collection for Four-Stroke Rich Burn Spark Ignited 

Reciprocating Internal Combustion Engines 

National Emission Standard for Hazardous Air Pollutants 

40 CFR, Part 63, Subpart ZZZZ

PREPARED FOR: 

1220 L Street NW 

Washington DC 20005

PREPARED BY:

Innovative Environmental Solutions, Inc. 

P.O. Box 177 

Cary, IL 60013-0177 

April 9, 2010 Rev 1 

16666 Northchase Drive 

Houston, TX 77060 15508 Wright Brothers Drive 

Addison, TX 75001 3809 South FM 1788 

Midland, TX 79706
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TABLE OF CONTENTS 

 Executive Summary....................................................................................................................ii 

1. Project Objectives and Data Sources........................................................................................... 1 

1.1. Formaldehyde Emissions Measurement Program ................................................................ 2 

1.2. Collection of Existing Formaldehyde Emissions Data......................................................... 4 

1.3. Summary of MACT Floor Database Engines and Tests ...................................................... 4 

1.4. Report Content...................................................................................................................... 4 

2. MACT Floor Determination: Basis and Analysis Approach....................................................... 6 

2.1. Identifying Best Performing Units ....................................................................................... 7 

2.2. MACT Floor Variability....................................................................................................... 9 

3. Data Summary and Discussion: Four-Stroke Cycle Rich Burn Engines.....................................12 

3.1. Selection of Best Performing Units......................................................................................12 

3.2. MACT Floor Variability for 4SRB Engines ........................................................................13 

4. Sized Based Subcategories ..........................................................................................................14 

5. Conclusions and Recommendations............................................................................................16 

6. Sources.........................................................................................................................................17 

Table 3-1: 4SRB “Best Performing” Engine Test Data Summary...................................................12 

Table 3-2: Summary of MACT Floor Engines.................................................................................13 

Appendix A: 4SRB Engine Test Data 

Appendix B: Data Review Process and Short Term Test Validation 

Appendix C: Formaldehyde Emissions Measurement Test Protocol 
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Executive Summary 

This report discusses and presents the data, analysis, and conclusions from a program to compile 

formaldehyde emissions testing data for four-stroke rich burn (4SRB) gas-fired engines. To address 

the need for additional formaldehyde emissions data and in response to a request by EPA to provide 

additional test data, Exterran, J-W Power Company, and Compressor Systems, Inc. (collectively 

referred to as "EJC") conducted an intensive field testing program directed at 4SRB engines less than 

500 hp. The American Petroleum Institute (API) supplemented and augmented the EJC field test data 

with existing test data. 

These data were developed to support comments previously submitted on the Reciprocating Internal 

Combustion Engines (RICE) National Emission Standards for Hazardous Air Pollutants (NESHAP) 

that EPA proposed on March 5, 2009. The data analysis and conclusions in this report are based on the

Clean Air Act, relevant court findings, and a test plan specifically designed to inform the MACT floor

analysis. 

The following two-step methodology was used to determine the 4SRB MACT floor: 

• The MACT floor 4SRB engines were first identified by sorting the engines based on the lowest 

(i.e., best performing) formaldehyde (CH2O) test for each engine, which compares the engines

on a common operating basis, and the best performing 12% were selected as MACT floor 

engines. 

• The MACT floor 4SRB emission limit was then determined by considering emissions 

variability from the population of the best performing 12% of all engines tested (i.e. the floor 

engines). All floor engine tests were reviewed to determine emission levels at all operating 

conditions that can be “reasonably expected to recur” and the highest level (i.e., 13 ppmvd @ 

15% O2) is the floor such that each MACT floor engine can “meet the standard every day and 

under all operating conditions.” 

Our method for identifying MACT floor engines, which is based on the lowest CH2O emissions, 

provides the best assurance that tests completed at similar operating conditions are compared on an 

equitable basis. Other methodologies contemplated by EPA have compared engines operating at 

vastly different loads or operating conditions. This would not be an accurate or equitable comparison

for selecting the “best performing” engines. Moreover, the approach for evaluating emission 

variability from the MACT floor engines is consistent with methodologies previously employed by 

EPA in other MACT rules and complies with the relevant D.C. Circuit Court rulings which provide 

that the best performing MACT floor engines should be able to achieve the resulting MACT floor 

emission standard at all times. 

The EJC and API member companies’ data collection effort produced the following results: 

• A total of 51 engines and 120 individual engine tests were analyzed for this technical report. 

• Seven (7) engines, 12% of the total, comprise the best performing MACT floor engines. 

• A total of 38 floor engine tests at a variety of operating conditions were used to assess 

variability. 

• The floor engine tests showed formaldehyde emissions ranging from 3.18 parts per million 

volumetric dry (ppmvd) to 12.05 ppmvd (corrected to 15% oxygen). 

EJC-API supports “work practice” standards for major sources, as an alternative to emission standards,

for engines with a rated capacity less than 300 hp. EJC-API supports “management practice” standards 
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for area source engines less than 500 hp. However, if EPA were to proceed with establishing an 

emission limit for 4SRB engines, EJC-API advocates establishing a MACT floor emission limit of no 

lower than 13 ppmvd @ 15% O2 that is supported by the test data and analyses. In reviewing this 

MACT floor emission limit, it should also be noted that the test program that provided all of the floor 

engines focused on engines located in southwestern states, where fuel quality and ambient temperature 

could have resulted in a low formaldehyde emission bias. For this reason, EJC-API requests that the 

EPA take into account variability issues that are pertinent to other regions of the United States (e.g., 

colder climate areas) and consider that best-performing engines in those areas may not be able to 

achieve an emission limit based on engine testing that did not implicate all potentially relevant 

emissions-affecting variables. 
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1.0 Project Objectives and Data Sources 

A rule to amend the Reciprocating Internal Combustion Engines (RICE) National Emission 

Standards for Hazardous Air Pollutants (NESHAP) was proposed on March 5, 2009. The 

proposal addresses reciprocating internal combustion (IC) engines that are located at area sources 

of hazardous air pollutants (HAPs), engines with a site rating of less than or equal to 500 

horsepower (hp) located at major sources of HAPs, and existing stationary compression ignition 

engines greater than 500 hp located at major sources. The Proposed Rule represents the third 

version of this NESHAP. In November 2009, EPA extended the Final Rule deadline for spark 

ignited (SI) RICE to August 10, 2010. 

As discussed during the comment period, stakeholders in the natural gas industry that own or 

operate natural gas-fired RICE are concerned about the paucity of test data that was relied on to 

support the MACT floor in the proposed rule. To address these concerns and in response to a 

request by EPA to provide additional test data, Exterran, J-W Power Company, and Compressor 

Systems, Inc. (collectively referred to as "EJC") conducted an intensive field testing program 

directed at 4-stroke rich burn engines less than 500 hp. EJC own and operate fleets of rental 

compressors that primarily service rural oil and gas exploration and production operations. 

These compressors are driven by natural gas-fired engines, and as proposed, this rule will 

significantly impact nearly every engine owned by EJC. 

The American Petroleum Institute (API) shared the same data concerns and has supplemented 

and augmented the EJC field test data with existing test data. API is a national trade association 

with more than 400 member companies involved in all aspects of the oil and gas industry. 

Natural gas-fired RICE represents the largest population of engines in the exploration and 

production, and transmission sectors for API member company operations. As the interests of 

both EJC and API are aligned in terms of the impacts associated with this rulemaking, EJC and 

API are submitting this technical report together and are referred to in this document as EJCAPI. 

The proposed rule impacts existing area source engines and establishes limits based on very 

limited emissions data associated with small natural gas fired reciprocating engines. In an effort 

to supplement the emissions data available for the rulemaking, EJC-API requested emissions 

data from its members. The objective of the data compilation was to: 

• Assess the availability of applicable emissions data for 4-stroke rich burn (4SRB) engines; 

• Collect available emissions data for 4SRB engines; 

• Compile and organize the data into a report for transmittal to EPA; and, 

• Review and analyze the data to assess implications for the emission standard, including the 

basis for the maximum achievable control technology (MACT) standard as required under 

the Clean Air Act. 

The Clean Air Act requires that the MACT standards for existing units at major sources be based 

on the average emission limitation achieved by the best performing 12% of engines in a 

subcategory (i.e., the “MACT floor”). In recent D. C. Circuit Court cases, discussed further in 

Section 2.2, the MACT floor emission limit can consider emission variability and must be 

achievable at all times and under the most adverse circumstances that are reasonably expected to 
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recur. This report discusses and presents the conclusions from the test program and 4SRB data 

analysis as it relates to the Clean Air Act, court findings, and test plan considerations. 

1.1 Formaldehyde Emissions Measurement Program

The proposed rule includes formaldehyde (CH2O) emission standards for rich burn engines. 

Since CH2O compliance testing is not required for many engines, it was expected that existing 

CH2O emissions data would be minimal. In anticipation of this lack of data, particularly as it 

relates to variable operating conditions, EJC implemented a robust testing program. 

The overall purpose of this testing program was to obtain emissions data to support revisions to 

the MACT floor limits in the upcoming Final Rule that will amend the NESHAP for 

reciprocating IC engines embodied in 40 CFR, Part 63, Subpart ZZZZ. Specifically, the MACT 

floor emissions test project objectives were to: 

1. Establish a test program to consistently obtain emission data for developing MACT floor 

emission limits that address the size, type, and operation of affected engines. The focus of 

the MACT floor testing program was directed toward smaller (less than 500 hp) natural gasfired engines. 

2. Obtain emissions data over the range of engine operating conditions that are expected to be in 

the MACT floor data set (i.e., engines in the best performing 12% of engines in the 4SRB 

subcategory) to allow determination of emission limits that include normal operational 

variability. Engine parameters that could impact emissions variability include: 

• Excess O2; 

• Percent load; 

• Multiple engines of identical make / model; 

• Fuel quality; and, 

• Ambient affects including temperature, relative humidity, & elevation. 

 

These specific MACT floor data objectives were established because EJC-API understands that, 

based on recent Circuit Court case decisions, EPA has the latitude to set the floor at a level that is

a reasonable estimate of the emissions from the best performing units under the worst reasonably 

foreseeable circumstances. The importance of this concept is addressed in more detail in Section 

2.2, which outlines the EJC-API approach to variability. 

A test plan was prepared that outlined the technical approach for data collection and the plan was 

provided to EPA in advance of field testing activities. In addition, test procedures and changes 

to data collection methodologies were discussed with EPA during several teleconferences and 

subsequent meetings. EPA provided concurrence on the data collection approach during an 

October 5, 2009 meeting with API. 

Several oil and gas producing areas that had a variety of engine make and models and ages of 

smaller (less than 500 hp) gas fired engines were identified for MACT floor testing activities. 

The primary goal was to identify sets of engines in close proximity to minimize time to mobilize 

to the next test location. For this reason, the testing program may have conservatively biased the 
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results lower as the average ambient temperatures from this region are higher than temperatures 

in northern tier States. 

Emission measurements were conducted in accordance with EPA and ASTM test methods. 

However, the data were not collected consistent with performance or compliance testing 

requirements (e.g. three one-hour tests at 100 + 10% engine load); rather the testing approach 

was to efficiently identify potential MACT floor engines and then test these engines over a range 

of operating conditions to assess emission variability. This approach was employed to maximize 

data collection in consideration of the time and testing resource constraints. To identify potential 

MACT floor units (i.e. best performing 12 %), the testing effort focused on comparing all 

engines on a common operating basis. In order to accomplish this goal, initial tests on engines 

were conducted by adjusting carburetor settings and fuel pressure to “manually adjust” the 

engine operation to an “expected” lower formaldehyde emissions operating point corresponding 

to an exhaust oxygen concentration of one half percent or less. 

Units with the potential for becoming MACT floor engines were then tested over a range of 

loads and air-to-fuel ratios using single one hour and shorter period tests. The shorter, single test

approach was employed to optimize emissions variability characterization (i.e. conduct as many 

tests as practical on an engine, given testing on an engine was typically limited to one day or 

less). This approach was discussed with Gary McAlister of EPA’s Emissions Measurement 

Center during the August 5, 2009 meeting at RTP and was tentatively approved based on a 

favorable comparison of the standard deviations among the short-term FTIR measurements and 

the 1-hour data sets. Additional detail regarding the testing procedures is provided in Section 

2.1and Appendix B. 

The project quality assurance/quality control (QA/QC) activities associated with the collected 

test data included review of emission measurement method performance requirements, engine 

operation monitoring equipment calibrations, and mass balance engineering calculations. 

QA/QC requirements for the instrumental emission measurement methods include interference 

checks, calibration error checks, system bias tests, drift checks, and linearity requirements. 

Emission test reports were reviewed for adherence to reference test methods and QA/QC results 

were compared to method performance requirements. 

Engine operating parameters were monitored during the testing to estimate engine operating load 

and fuel consumption. These parameters included compressor suction and discharge gas 

pressures and temperatures, and fuel gas flow rate. Compressor suction and discharge pressures 

were typically measured by control panel pressure gauges. These panel gauges were then 

calibrated against a reference pressure gauge and test data adjusted accordingly. Compressor 

temperatures were typically measured with a panel meter and a second temperature by an IR 

meter or thermocouple was conducted to verify the measurement. Fuel gas flow rate was 

measured using rotary gas meters. These meters measure actual gas volume and thus require gas 

pressure and temperature measurements to determine fuel flow at standard pressure and 

temperature. Post test calibrations of the rotary flow meters and pressure gauges were conducted 

and measurement data adjusted accordingly. 
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QA/QC activities also included calculation of engine brake-specific fuel consumption (BSFC) 

based on fuel use and engine load measurements. BSFC is calculated as Btu/hp-hr and is a 

measure of engine efficiency. BSFC is impacted by numerous parameters - including engine 

design, load, age, maintenance schedule, and fuel properties and ambient conditions - and can 

range considerably, especially at lower loads for older engines. BSFC values calculated from 

engine fuel use and load measurements were compared to the expected BSFC range to assess the 

measurements. For engines with calculated BSFC outside the expected range, measurement 

data were further examined and the data noted. Uncharacteristic BSFC values for some MACT 

Floor engines were caused by a damaged fuel gas pressure gauge and the resulting erroneous fuel 

consumption. Appendix B includes additional discussion of QA/QC measures taken to ensure 

data objectives are met. 

1.2 Collection of Existing Formaldehyde Emissions Data

Because formaldehyde emissions testing has typically not been required for smaller engines, 

very little emissions data exist for engines less than 500 hp, which are primarily located at rural 

sources. API members compiled and provided a minimal amount of data summaries for review 

and inclusion in the MACT floor analysis. 

1.3 Summary of MACT Floor Database Engines and Tests

Fifty one (51) 4SRB engines with rated capacities of between 100 hp and 500 hp were included 

in the MACT Floor analysis. The majority of the 4SRB engines tested were Caterpillar (37) and 

Waukesha (13), with one engine from Cummins (1). Thirty one (31) of the fifty one (51) 

engines had multiple tests conducted. Within the population of the best performing twelve 

percent engines, thirty eight (38) individual tests were completed. These data are further 

discussed in Sections 2 and 3. 

1.4 Report Content

The data collection effort compiled a significant amount of CH2O data for rich burn engines. 

These data are useful for demonstrating engine operation, emissions variability, and informing 

MACT floor emission limits that can be achieved at all times and under the most adverse 

circumstances which can reasonably be expected to recur. This report presents and summarizes 

the results of the 4SRB engines CH2O emissions data collection effort. 

While this is primarily a “data report”, the document includes analysis and discussion that 

provides a technical summary of the CH2O emissions data. Section 2 provides a discussion of 

“MACT floor” analysis based on the EJC-API understanding of Clean Air Act requirements and 

recent court cases, including assessment of the best performing 12% of engines and variability 

within the MACT floor engine population. Section 3 presents summary data and tables for the 

4SRB engine subcategory. Section 4 discusses the resulting size based subcategories for the 

4SRB engines. Section 5 summarizes the results and provides concluding remarks. 

The detailed data and quality assurance / quality control (QA/QC) information are provided in 

the appendices. Appendix A provides data tables for the 4SRB engines that include a unique 

engine identifier, unique test identifier, engine information (e.g., make, model, type), test 

information (e.g., test date, test method, engine load), and emissions data. Appendix B discusses 
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QA/QC review of data and the standard methods used for testing. Appendix B also includes a 

discussion of the representativeness of short-term (i.e., less than 1-hour) test runs conducted for 

the purpose of assessing emissions variability. In addition to these appendices, an Air Hygiene 

source test report for engines that populate the MACT floor will be provided to EPA separately. 

This third party test report contains a summary of the engine make, model, OEM horsepower, 

test condition, altitude, ambient conditions, fuel analysis, sampling and analytical procedures, 

test results and calculations, and QA/QC for the test program. 
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2.0 MACT Floor Determination: Basis and Analysis Approach 

Section 112(d)(3)(A) of the Clean Air Act requires that the emission standards for existing 

engines at Major Sources be based on “the average emission limitation achieved by the best 

performing 12% of the existing sources...”. This emission level is typically referred to as the 

“MACT floor”. The MACT floor determination is a two step process. The MACT floor engines 

are first identified and then the entire emissions database for these MACT floor engines is then 

considered to determine the level of the standard. The consideration of the entire emissions 

database stems from recent decisions from the D.C. Circuit Court (Court) that supported the 

consideration of variability in establishing emission standards. 

For this analysis, EJC-API considered the Clean Air Act, Court decisions regarding the basis for 

determining Section 112(d) emission standards, the EPA analysis for existing compression 

ignition engines in the March 3, 2010 RICE NESHAP amendments, and recent EPA MACT 

floor analyses from other NESHAP rules. In addition, this analysis is supplemented by our 

understanding of reciprocating engine emissions, the inherent variability in emissions from 

natural gas-fired reciprocating engines, and operating conditions such as load that can affect rich 

burn engine CH2O emissions. 

For rich burn gas-fired engines, the proposed rule establishes CH2O as the regulated HAP. Since 

CH2O measurement is not common in compliance tests, available tests results for affected 

engines did not offer sufficient data to determine the MACT floor or to address variability. 

Consequently, EJC implemented the testing program described above in Section 1.1. 

In advance of EPA’s MACT floor analysis, EJC-API is providing this document to illustrate our 

MACT floor analysis and consideration of variability. Our methodology is based on Clean Air 

Act requirements and recent Court directives for establishing a MACT floor emission limit that 

must be met every day under all operating conditions. Because there are many existing SI RICE 

and it is not practical or feasible to expect stakeholders to develop a detailed understanding of 

emissions from all engines during this rulemaking, any available dataset will have inherent 

limitations or deficiencies, and those limitations need to be carefully assessed in the analysis. 

For example, although this report provides data from more than 50 engines, there are practical 

limitations that could lead to an unreasonable conclusion depending upon the technical analysis 

of the data. For illustration, a best performing engine located at approximately sea level and 

tested at warm ambient temperatures may result in lower formaldehyde emissions; that same 

engine located at higher altitudes and colder ambient temperatures would likely have higher 

formaldehyde emissions. These and other factors that may affect emission variation are 

discussed in Section 2.2. 

 

Sections 2.1 and 2.2 provide the EJC-API analysis and discussion on the technical perspective of 

the data collected by EJC-API, including identification of the “MACT floor” engines and 

consideration of variability. These sections also discuss the field test program design 

considerations as they relates to the MACT floor analysis. 
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2.1 Identifying Best Performing Units 

This section addresses two issues related to identifying the MACT floor units: averaging of 

numerous test runs from a single engine operating or test condition (i.e. emission test averages) 

and engine-to-engine comparisons when emission measurements were conducted at multiple 

engine operating/test conditions. These issues are discussed with consideration of the EJC 

testing program that collected the majority of the emission data. 

As described in Section 1.1, a test plan was developed, adjusted, and communicated to EPA to 

focus limited resources toward completing data collection and inform MACT floor decisions. 

The overall goal of this test program was to maximize the number of MACT floor test engines 

and complete testing over a range of expected operating conditions to inform emissions 

variability from potential MACT floor engines. A deliberate approach (i.e. reduce the number of 

variables potentially impacting the emissions) designed to identify the best performing 12 

percent of 4SRB engines was adopted following initial field tests by conducting subsequent tests 

on all units at a consistent, lower excess air/O2 setting. 

Consequently, all rich burn engines were tested at a common operating condition, the highest 

available load and a common excess air/O2 setting of 0.5% or lower. This approach was adopted 

to maximize the opportunity for identifying MACT floor engines, and minimize resources 

required to test the engine population within the lower 88 percentile engine population. Once a 

candidate MACT floor engine was identified, the engine would be tested at several excess air 

settings/air-to-fuel ratios (up to 2% O2) and/or loads (i.e. depending on ability to adjust or alter 

work) to determine expected emission variability (i.e. variability based on operating envelope). 

The MACT floor engines are based on the test data at the common operating condition. 

However, the MACT floor emission limit would be based on the emissions over the range of 

loads and/or air-to-fuel ratios (i.e., emission limit considers variability) as discussed further in 

Section 2.2. 

EJC-API understands that for the March 2010 compression ignition NESHAP amendments, 

when multiple “test runs” are available for a single “test” condition, such as three high load test 

runs for a compliance test, EPA used the average of the three runs when comparing emissions 

data between engines to identify the best performing 12%. If only a single test run is available 

for a particular engine operating condition (e.g., most EJC tests), then that test result is used for 

the comparison between engines to identify the best performing 12%. EJC-API supports this 

approach as is further discussed in Section 3. 

The next step is to consider how to evaluate engines and compare data between engines when 

some engines have multiple tests. In the EJC-API data set, most engines were tested at multiple 

operating conditions and only one engine has multiple test runs at the same operating condition. 

As described below, EJC-API strongly recommends that for engines with multiple CH2O 

emission tests, the lowest or best performing CH2O emissions from each engine should be used 

for engine-to-engine comparisons to identify the best performing 12%. This approach provides 

the best assurance that tests completed at similar operating conditions are equitably compared

when defining the engines in the top 12%. 
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EPA has previously considered potential approaches to determining the MACT floor that 

included using either the highest CH2O test result or averages from multiple test points at 

disparate operating or test conditions. EJC-API believes that it is inappropriate to select the 

MACT floor engine using either of these approaches and that the selection methodology 

described in this report is more technically defensible, particularly when there are multiple 

engines in the MACT floor. To further clarify the rationale for selecting the lowest or best 

performing CH2O emissions units, consider the limitations introduced by selecting the highest 

CH2O emissions to identify the MACT Floor unit. If the top 12% is selected based on comparing 

the highest CH2O from multi-test engines (i.e., the engines are sorted from lowest to highest 

based on the highest emission test condition), it is likely that an operating condition with higher 

characteristic emissions (e.g., lower load and/or higher AFR) from the multi-test engines would 

be compared to a high load/low AFR test (lower characteristic emissions) for the single-test 

engines. This is an inequitable comparison: 

• which precludes the comparison of CH2O data at common operating conditions (e.g., high 

load and nominal AFR) for the multi-test versus single test engines; 

• would likely result in single test engines in the MACT floor although they have higher 

emissions than the multi-test engine at a common operating condition; 

• prevents consideration of operating conditions that reflect “best performance” for multi-test 

engines; and 

• could result in multi-test engines being precluded from or limited in the population of 

engines in the best performing 12%. 

This approach would also result in limited data for assessing variability and is in direct conflict 

with the test plan that was developed with the express purpose of gathering formaldehyde 

emissions data over a range of achievable engine operating conditions. Under this very plausible 

scenario the single test engine could be in the MACT floor although it may have higher 

emissions than the multi-test engine at a common operating point. Using the average of multiple 

test conditions across divergent operating conditions is similarly inappropriate for assessing the 

MACT Floor technologies (i.e., engine make and model). 

EJC-API believes that the most logical and technically defensible approach is to compare 

engine-to-engine data under similar operating conditions where feasible, and that such a 

comparison has a higher probability of identifying the better performing engines. For example, 

comparing CH2O emissions from two engines at a common operating condition (e.g., highest 

available load and a common excess air/O2 setting of 0.5% or lower) provides an indication of 

the better performer. However, comparing high load/low excess air emissions (with lower 

characteristic CH2O) from one engine with low load/high excess air emissions (with higher 

characteristic CH2O) from another engine is not equitable. The floor engine selection process 

must provide a reasonable basis for assessing which engine is the better performer and 

significant discrepancies in key operating parameters (e.g., AFR, load) that are known to impact 

CH2O emissions precludes a rational comparison. 

Engine emission characteristics also support the common operating condition comparison that is 

best achieved by comparing lowest emissions from multi-test engines. For example, for rich 

burn reciprocating engines, it is generally expected that CH2O emissions are more variable 
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across the range of typical engine conditions (e.g., load and AFR) on an individual engine than 

the variability that would be reflected by comparing multiple similar engines at a common high 

load operating condition. If all engines in the dataset were tested under a similar range of 

operating conditions and had a similar number of test points, this issue would be less compelling. 

However, for the data provided in this report, where the number of tests per engine varies from 

one or two tests on many engines to as many as seven tests on other engines, this analytical 

approach is important not only for defining best performers, but also for providing the ability to 

consider data from multiple tests to better understand emissions variability. 

While not detailed in this report, review of the EJC-API dataset confirms the concerns expressed 

here. When the data are sorted based on the best performing or lowest CH2O emissions for 

multi-test engines, the result is many engines with multiple tests in the MACT floor (i.e., a total 

of 38 individual tests from 7 MACT floor engines further detailed in Section 3). In contrast, 

sorting the engines based on maximum emissions results in 16 tests to assess variability, with 

five of the seven engines having either one or two test runs. The latter approach limits and 

significantly hinders the ability to assess emissions variability for the best performing 12% of 

engines. 

Thus, it is imperative that the “best performing” engines within a subcategory be based on 

selecting the lowest CH2O test from multi-test engines for comparison with other engines. EJCAPI believes that this approach is consistent with the Clean Air Act and has the most technical 

merit for identifying best performing engines. In addition, this approach is consistent with the 

EJC testing that is the source of the majority of the test data; engines that were initially identified 

as best performers were subsequently tested at lower loads and higher AFRs that resulted in 

higher CH2O emissions. Conversely, engines that were not initially identified as best performers 

were not subsequently tested at operating conditions expected to produce higher CH2O 

emissions. Thus, the only equitable engine-to-engine comparison for EJC tested engines is at the 

common, best performance operating condition. Finally, because this approach will limit the 

likelihood that multi-test engines will be inappropriately excluded from the “MACT floor” 

engine population, this approach also facilitates consideration of the range of emissions for best 

performing engines and CH2O emissions variability. Section 3 of this report uses this approach 

for identifying the engines in the “MACT floor”. 

2.2 MACT Floor Variability 

EPA has indicated that review of emissions variability should be limited to the “MACT floor” 

units (i.e., the engine population in the best performing 12%). This report does not discuss 

possible alternatives to this interpretation for the variability assessment, but this approach does 

introduce limitations when considering the vast array of engine types and applications. The 

limited resources and regulatory timeframe did not allow for an extensive test program to 

provide a wide range of engine make/models, altitudes, ambient conditions, fuel quality, and 

applications to be comprehensively evaluated. Establishing an emission limit based on limited 

test data from a very large population of affected sources emphasizes the need to properly 

characterize variability from the test data set. Therefore, it is imperative that EPA consider the 

limited dataset over the entire population of MACT floor engines to assess variability. 
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For example, it is commonly understood that fuel quality, ambient conditions (e.g., temperature, 

humidity or precipitation), and elevation can impact emissions. Both higher elevation and cooler 

ambient temperature are likely to result in an increase in CH2O emissions. Additionally, reduced 

fuel quality, not uncommon for field gas-fired engines, impacts combustion and could increase 

products of incomplete combustion (i.e. formaldehyde). If data from the MACT floor engine 

population are limited to engines at lower elevation and/or from warmer weather tests, as is the 

case for many of the EJC-API tests, then variability associated with these factors will not be 

captured. Furthermore, the field gas fuel for the EJC-API tests was generally of high quality (i.e. 

high methane and low diluent content) and promoted stable combustion. It should be noted that 

some engines with multiple tests over a broad range of operating conditions may provide 

informative emissions variability data, but if the lowest CH2O emissions are not within the best 

performing 12%, then that data set is not included in the analysis (e.g., key emissions 

information related to variability is lost). 

This report is an “emissions data report” with complementary technical discussion. Thus, 

detailed citations and legal justification are not provided, but recent Court decisions provide 

insight into assessing variability when establishing the MACT floor for existing engines. The 

2007 Brick MACT encapsulates many of these decisions by referring to the recent record from 

similar challenges. Examples supporting EPA’s ability to incorporate variability in the MACT 

floor include: 

• The Brick MACT decision reiterates a finding from the 2001 Cement Kiln MACT (“Cement 

Kiln”) decision and a related 1999 decision where the D.C. Circuit Court explained, “EPA 

would be justified in setting the floors at a level that is a reasonable estimate of the 

performance of the ‘best controlled similar unit’ under the worst reasonably foreseeable 

circumstances.” 

• “Cement Kiln” also acknowledges that it is acceptable for EPA to consider the range of 

emissions from the best performing sources and that results at more adverse conditions “are 

more helpful than normal operating data would be in estimating performance under a variety 

of conditions and thus in helping to assure that properly designed and operated sources can 

achieve the standard.” 

• The Brick MACT decision also references the 2003 Mossville Environmental Action versus 

EPA decision in which the D.C. Circuit Court “...held that floors may legitimately account 

for variability because “each [source] must meet the [specified] standard every day and under 

all operating conditions.” 

• A similar premise is evident in a 1999 Sierra Club versus EPA decision noting that the 

MACT floor standard must be achieved at all times and, “under the most adverse 

circumstances which can reasonably be expected to recur.” 

Thus, it is acceptable and expected for EPA to consider emission levels associated with normally 

anticipated and recurring operating conditions, and Court decisions acknowledge that data from 

more adverse operating conditions can inform the basis of the standard. For the context of the 

rich burn engine emission standard considered in this report, higher CH2O emissions associated 

with reasonable operating conditions likely to recur are of special interest. These operating 

conditions and associated emissions are of interest due to the nature of the dataset, where low 

elevation, warm ambient temperature tests are prevalent due to location and timing of the engine 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

11 

testing. Thus, the data distribution is not indicative of the entire population of engines operations

and more adverse conditions (for CH2O emissions) such as higher elevation operation, cold 

ambient temperatures, and poor fuel (field gas) quality are under-represented in the MACT floor 

units. 

In addition to the items listed above, Court cases buttress EPA’s position that the floor should 

not be based on “worst performer” units with the MACT floor technology (i.e., rich burn engines 

without HAP control for this standard) that are not within the best performing 12%. For 

example, the Brick MACT decision references a Cement Kiln MACT finding, “...that EPA may 

not use emission levels of the worst performers to estimate variability of the best performers 

without a demonstrated relationship between the two...” While demonstrating a relationship 

could provide an avenue to consider variability from units outside the top 12% (e.g., a unit not 

within the floor that is the same make and model as a MACT floor unit, but located at a different 

elevation), this is not pursued in the analysis discussed in Section 3. 

Furthermore, case law supports establishing a MACT floor to reflect the impact that external 

sources, such as ambient conditions and fuel, may have on the best performers' emissions. In 

Mossville Environmental Action versus EPA, the court supported EPA's decision to evaluate 

emissions from all plants in a sector, and not the just the plants in the top 12%, because emission 

variability was driven by "the type of resin being produced, not the technology or processes 

applied to control emissions." As referenced above, the Brick MACT court recognized that the 

MACT emission standard may account for variability because the standard must be "met all day 

every day" and that the final emission standard in Mossville reasonably estimated that variability 

for the best performing source. 

In summary, in considering variability, EJC-API is recommending that EPA: 

• incorporate the range of emissions from best performing engines into the standard setting 

process; 

• consider that the operating conditions associated with higher CH2O test results points are 

within the envelope of reasonable operations and likely to recur; 

• consider that the CH2O emission data distribution here is not indicative of the entire 

population of engines operations and more adverse conditions (for CH2O emissions) such as 

fuel quality, altitude effects, ambient temperature, and humidity effects are underrepresented. 

• consider that the resulting 4SRB MACT floor is considered conservative and would be 

expected to increase if these adverse conditions discussed above would have been included 

within the test program; 

• consider that the units must meet the standard every day and under all operating conditions; 

and 

• establish a standard that MACT floor units can meet if operating “under the most adverse 

circumstances which can reasonably be expected to recur.” 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

12 

In Section 3, data are summarized for the engines that comprise the best performing 12%. The 

analysis and discussion follow the principles discussed above, and the following sections 

illustrate these principles based on the CH2O emissions data collected by EJC-API. 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

13 

3.0 Data Summary and Discussion: Four-Stroke Cycle Rich Burn Engines 

To determine the number of 4SRB engines in the best-performing 12 percent, the number of 

engines was multiplied by 12 percent and rounded up. For the data discussed in this section, 51 

engines were tested and 12% equates to 6.12, which places 7 engines into the MACT floor. A 

total of 120 engine tests are associated with the fifty one 4SRB engines that have rated capacities 

between 100 and 400 horsepower (hp). The majority of the 4SRB engines tested were 

Caterpillar (37) and Waukesha (13), with one engine manufactured by Cummins. The majority 

of the engine tests were supplied via the engine testing program managed by EJC. As discussed 

above, numerous parameters are expected to impact formaldehyde emissions from 4SRB engines 

including load, fuel quality, excess air, engine age and maintenance practices/schedule, 

elevation, and ambient conditions. While the project attempted to test engines over their asfound operating envelop, the testing was not designed to be a parametric investigation and a 

quantified evaluation of the individual parameters impacting CH2O emissions was well beyond 

the scope of this testing project; however, the data generally show CH2O emissions increasing 

with lower load and higher excess air. 

3.1 Selection of Best Performing Units

Table 3-1 summarizes the primary formaldehyde emission test data set for the ten best 

performing 4SRB engines with rated capacities of between 100 hp and 500 hp. The full set of 

engine test data is provided in Appendix A. As discussed above, the 51-engine dataset results in 

a MACT floor (top 12%) comprising the seven engines having the lowest formaldehyde 

concentration in any single test. 

Table 3-1. 4SRB “Best Performing” Engines Test Data Summary 

Engine 

No.

Test 

No. Make Model Test Date Test Method

Rated 

HP CH2O1

17 T36 Waukesha F1197GU 9/23/2009 RM 320 192 3.18

43 T105 Caterpillar 3306 TA 10/8/2009 RM 320 203 3.31

21 T47 Caterpillar 3406 TA 9/24/2009 RM 320 325 3.53

5 T9 Caterpillar G-342TA 9/11/2009 RM 320 265 4.71

14 T26 Waukesha F1197GU 10/1/2009 RM 320 192 4.72 MACT FLOOR ENGINES

34 T75 Waukesha F1197G 9/30/2009 RM 320 192 4.94 (Top 12%)

38 T88 Waukesha F1197G 10/2/2009 RM 320 192 4.96

41 T100 Caterpillar G3406TA 10/6/2009 RM 320 325 5.52

15 T30 Caterpillar 3306 NA 9/21/2009 RM 320 145 5.52 NON-FLOOR ENGINES

42 T102 Caterpillar 3406 TA 10/7/2009 RM 320 325 5.97 (Portion of Bottom 88%)

NOTE1: ppmvd @ 15% O2 during best performing test for the engine

RM: EPA Reference Method
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

14 

3.2 MACT Floor Variability for 4SRB Engines

To assess emissions variability for the best performing 12% of 4SRB engines, emission levels 

associated with the tested range of operating conditions for the MACT floor engines were 

considered. Table 3-2 summarizes the MACT floor engines CH2O emission test data. A review 

of the operating conditions for the 38 MACT floor engine tests determined that all tests were 

conducted during routine operating conditions that will recur. In addition to presenting the range 

of test data points, Table 3-2 also presents the number of tests associated with each engine. The 

number of tests provides an indication of the ability to assess variability from the MACT floor 

engine population (i.e., emissions information from a single engine at multiple operating 

scenarios). Without multiple test points at different engine operating conditions, variability 

cannot be assessed. 

It should be noted that this data set is still relatively limited and the tests were conducted at a 

single point in the engine’s operation; thus, the available emission data surely do not reflect 

inherent variability that will occur over time (e.g. caused by different load, ambient conditions, 

fuel quality, time lapse since maintenance/overhaul, etc.) nor capture more adverse conditions 

that are likely to occur and could increase emissions of formaldehyde as well as other products of 

incomplete combustion. Thus, it is reasonable to conclude that the upper bound of these MACT 

Floor engines test results reflects some, but not all, of the variability for best performing units. A 

complete summary of the entire test data set is contained in Appendix A. Note that one engine 

(i.e., No. 51 listed in Appendix A within the lower 88 percentile) contains multiple test runs at 

the same engine operating/test condition and therefore an average of these four test runs were 

used in the MACT floor engine selection for this source. 

 

Table 3-2. Summary of MACT Floor Engines. 

Engine 

No. Make Model Rated HP

MIN 

CH2O

1

MAX 

CH2O

1

# 

Tests

17 Waukesha F1197GU 192 3.18 7.59 3

43 Caterpillar 3306 TA 203 3.31 8.64 4

21 Caterpillar 3406 TA 325 3.53 10.94 5

5 Caterpillar G-342TA 265 4.71 12.05 6

14 Waukesha F1197GU 192 4.72 9.42 7

34 Waukesha F1197G 192 4.94 7.71 6

38 Waukesha F1197G 192 4.96 7.92 7

NOTE1: ppmvd @ 15% O2 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

15 

4.0 Sized Based Subcategories 

Section 112(c)(1) of the Clean Air Act (CAA) grants EPA broad discretion to establish 

“categories and subcategories” of sources to be regulated under §112. Additionally, CAA 

§112(d)(1) provides that the Administrator “may distinguish among classes, types and sizes of 

sources within a category or subcategory” when establishing MACT standards. 

In the final compression ignition rule (FR 9648 Vol. 75, No. 41) EPA promulgated work practice 

standards instead of numerical emissions limits for engines less than 100 hp at major sources. 

For SI engines, which have a very different emissions profile than CI engines, EJC-API believes 

that work practice standards should apply to engines less than 300 hp at major sources. EJC-API 

believes that it is appropriate to establish a higher size threshold for gas fired engines based on 

health effects issues surrounding diesel particulate that do not pertain to gas fired engines. 

Because of the difference in emissions between CI and SI engines, it is hard to justify the cost of 

emissions testing for engines less than 300 hp even at major sources. 

For major sources, CAA §112(h) indicates that “if it is not feasible in the judgment of the 

Administrator to prescribe or enforce an emission standard for control of a hazardous air 

pollutant or pollutants, the Administrator may, in lieu thereof, promulgate a design, equipment, 

work practice, or operational standard, or combination thereof”. EJC-API strongly encourages 

the use of work practice standards of CAA §112(h) for major sources in lieu numerical standards 

for 4SRB engines with rated capacities of less than 300 hp. 

The Clean Air Act gives EPA even more discretion for engines located at area sources, rather 

than major sources. For area sources, section 112(d)(5) allows “Generally Achievable Control 

Technology” (GACT) to be less stringent than major source MACT and also allows management 

practices in lieu of emission standards. EJC-API strongly encourages the use of management 

practice standards of CAA §112(d)(5) for area sources in lieu numerical standards for 4SRB 

engines with rated capacities less than 500 hp. The majority of the natural gas SI RICE 

population is understood to be predominately rural area source engines whereas HAP emission 

limits from stationary RICE are principally an urban risk-driven requirement. 

If EPA were to require a numerical emission limit for 4SRB engines, EJC-API advocates 

establishing a MACT floor of no lower than 13 ppmvd @ 15% O2 (i.e., maximum emission 

value for MACT Floor engines in Table 3-2, 12.05 ppmvd @ 15% O2, rounded to the next whole 

number) for all regulated 4SRB engines based on the analysis and results presented in Sections 2 

and 3. However, it should be further noted that the emissions data from the test program that 

supports this emission limit are conservatively biased low because limited test data was obtained 

during better than average conditions (warm climate, low elevation and good fuel quality). EJCAPI believes that if additional testing would have been conducted to quantify these operating 

(e.g., fuel quality, maintenance schedule) and ambient (e.g., temperature, altitude, humidity) 

parameters expected to impact formaldehyde emissions, the resulting MACT floor emission limit 

would have been higher. 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

16 

5.0 Conclusions and Recommendations 

EJC-API understand that the Clean Air Act requires that the emission standard for existing units 

located at major sources be based on the average emission limitation achieved by the best 

performing 12% of engines in a subcategory. The courts have also emphasized, however, that 

EPA must set floor limits that reflect emissions during operating conditions that can be 

“reasonably expected to recur”. We have established in previous comments to this rule and other 

rules that emissions from engines are extremely sensitive to operating conditions that can vary in 

terms of ambient conditions (temperature, humidity, and altitude), fuel quality, load, air/fuel 

ratio, and many other parameters. The concept of variability, which directly addresses this 

sensitivity, must be reflected properly in the final rule. With this concept in mind, EJC-API 

request that EPA implement the MACT floor analytical methodology presented in this 

document. 

The technical merits of our approach can be summarized as follows. 

• In terms of MACT Floor engines selection, the EJC-API methodology identified the “best 

performing” engines by comparing the emissions at common operating conditions that were 

found to be the best performing conditions for such engines. Other methodologies 

contemplated by EPA have compared engines operating at vastly different loads or operating 

conditions, which would not allow for a meaningful comparison when selecting the “best 

performing” engines. 

• In terms of variability assessment, the EJC-API methodology allows for emissions at 

operating conditions that can be “reasonably expected to recur”. Other methodologies used 

by EPA in other MACT rules mirror the EJC-API analysis, which reinforces the theoretical 

basis of this method (i.e., a floor engine should be able to meet the standard). 

Finally, we are recommending the following specific elements be included in the final rule. 

1. Management practice standards should be employed in lieu of an emission limit for area 

source engines with rated capacities less than 500 hp. 

2. Work practice standards should be employed in lieu of an emission limit for major source 

engines with rated capacities less than 300 hp. 

3. Based on the range of emission values presented in Table 3-2 and considering the 

technically sound methodology presented in this document, if a numerical MACT floor 

emission limit for the 4SRB engines is established by EPA, the limit should be set no 

lower than 13 ppmvd (at 15% O2). 

 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

17 

6.0 Sources 

The following sources of information were utilized in preparation of this report. 

1. National Emission Standards for Hazardous Air Pollutants for Reciprocating Internal 

Combustion Engines: Proposed Rule – Federal Register Volume 74, pages 9698 through 

9731 (dated March 5, 2009) 

2. “Comments On The Proposed Revisions To The National Emission Standards For 

Hazardous Air Pollutants For Reciprocating Internal Combustion Engines” – Docket 

Document Nos. EPA-HQ-OAR-2008-0708-0242.1 & 0242.2 submitted by API (dated 

June 3, 2009) 

3. “Exterran Technical Comments on the Proposed Revisions To The National Emission 

Standards For Hazardous Air Pollutants For Reciprocating Internal Combustion Engines–

submitted dated June 3, 2009 

4. Letter from Stephanie Meadows (API) to Melanie King (EPA) dated August 3, 2009 

providing a list of issues and meeting agenda 

5. August 5, 2009 meeting with EPA and API 

6. Letter from Jeff Holmstead to Robert Wayland dated August 17, 2009 outlining project to 

collect engine emissions data to support NESHAP development 

7. On 8-18-09 EJC meeting with EPA on August 18, 2009 to discuss testing protocol and 

other issues. 

8. “40 CFR 63 Subpart ZZZZ - Natural Gas Fired Engine MACT Floor Test Plan & 

Equipment / Operations Information Gathering” by IES (dated October 2, 2009) – also 

provided as Appendix C to this document 

9. Test Method 320: Measurement Of Vapor Phase Organic And Inorganic Emissions By 

Extractive Fourier Transform Infrared (FTIR) Spectroscopy added to Appendix A of 40 

CFR 63 

10. National Emission Standards for Hazardous Air Pollutants for Reciprocating Internal 

Combustion Engines; Final Rule - Federal Register Volume 75, pages 9648 through 9690 

(dated March 3, 2010) 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

APPENDIX A 

4SRB ENGINE TEST DATA 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-1 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

1 T1 Caterpillar 3306 NA As Found - 1 hr Test 9/9/2009 RM 320 145 73.4% 2 T2 Caterpillar G3406 TA As Found - 1 hr Test 9/10/2009 RM 320 325 57.6% 2 T3 Caterpillar G3406 TA O2-1% Period Test 9/10/2009 RM 320 325 -- 2 T4 Caterpillar G3406 TA O2-1.9% Period Test 9/10/2009 RM 320 325 -- 3 T5 Caterpillar G3306 NA As Found - 1 hr Test 9/10/2009 RM 320 145 66.0% 3 T6 Caterpillar G3306 NA O2-1.9% Period Test 9/10/2009 RM 320 145 -- 3 T7 Caterpillar G3306 NA O2-1% Period Test 9/10/2009 RM 320 145 -- 4 T8 Waukesha F11976 As Found - 1 hr Test 9/11/2009 RM 320 192 70.1% 5 T9 Caterpillar G-342TA As Found - 1 hr Test 9/11/2009 RM 320 265 70.9% 5 T10 Caterpillar G-342TA As Found, Low O2 9/11/2009 RM 320 265 63.4% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-2 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

5 T11 Caterpillar G-342TA High Load, Low O2 9/11/2009 RM 320 265 73.6% 5 T12 Caterpillar G-342TA High Load, High O2 9/11/2009 RM 320 265 73.6% 5 T13 Caterpillar G-342TA Low Load, High O2 9/11/2009 RM 320 265 37.7% 5 T14 Caterpillar G-342TA Low Load, Low O2 9/11/2009 RM 320 265 37.7% 6 T15 Caterpillar 3306 NA As Found - 1 hr Test 9/14/2009 RM 320 145 65.6% 7 T16 Waukesha F1197GU As Found - 1 hr Test 9/14/2009 RM 320 192 64.2% 8 T17 Caterpillar G3408TA As Found - 1 hr Test 9/15/2009 RM 320 400 59.5% 9 T18 Caterpillar 3306 NA As Found - 1 hr Test 9/15/2009 RM 320 129 57.7% 

10 T19 Caterpillar G3306 NA As Found - 1 hr Test 9/15/2009 RM 320 145 32.3% 11 T20 Caterpillar G3406 NA As Found - 1 hr Test 9/16/2009 RM 320 192 37.4% 12 T21 Caterpillar 3306 NA As Found - 1 hr Test 9/17/2009 RM 320 145 80.6% 13 T22 Caterpillar 3306 As Found - 1 hr Test 9/19/2009 RM 320 145 35.8% 14 T23 Waukesha F1197GU As Found - 1 hr Test 9/19/2009 RM 320 192 39.6% 14 T24 Waukesha F1197GU As Found - Retest 10/1/2009 RM 320 192 55.7% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-3 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

14 T25 Waukesha F1197GU As Found, Low O2 10/1/2009 RM 320 192 55.7% 14 T26 Waukesha F1197GU High Load, Low O2 10/1/2009 RM 320 192 63.5% 14 T27 Waukesha F1197GU High Load, High O2 10/1/2009 RM 320 192 63.5% 14 T28 Waukesha F1197GU Low Load, High O2 10/1/2009 RM 320 192 41.7% 14 T29 Waukesha F1197GU Low Load, Low O2 10/1/2009 RM 320 192 41.7% 15 T30 Caterpillar 3306 NA As Found - 1 hr Test 9/21/2009 RM 320 145 69.7% 15 T31 Caterpillar 3306 NA As Found - Retest 10/2/2009 RM 320 145 85.5% 15 T32 Caterpillar 3306 NA As Found, Low O2 10/2/2009 RM 320 145 85.5% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-4 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

15 T33 Caterpillar 3306 NA Mid O2 10/2/2009 RM 320 145 85.5% 16 T34 Caterpillar G342TAW As Found - 1 hr Test 9/23/2009 RM 320 265 33.2% 16 T35 Caterpillar G342TAW As Found, High O2 9/23/2009 RM 320 265 33.2% 17 T36 Waukesha F1197GU As Found - 1 hr Test 9/23/2009 RM 320 192 35.9% 17 T37 Waukesha F1197GU As Found, High O2 9/23/2009 RM 320 192 35.9% 17 T38 Waukesha F1197GU Mid Load 9/23/2009 RM 320 192 53.6% 18 T39 Caterpillar G3306NA Low O2 - 1 hr Test 9/23/2009 RM 320 145 59.5% 18 T40 Caterpillar G3306NA As Found 9/23/2009 RM 320 145 -- 19 T41 Caterpillar 3306NA Low O2 - 1 hr Test 9/23/2009 RM 320 145 57.5% 19 T42 Caterpillar 3306NA As Found 9/23/2009 RM 320 145 -- 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-5 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

20 T43 Caterpillar G3306NA Low O2 - 1 hr Test 9/23/2009 RM 320 145 70.4% 20 T44 Caterpillar G3306NA As Found 9/23/2009 RM 320 145 -- 21 T45 Caterpillar 3406 TA Low Load, Low O2, 1 

hr

9/24/2009 RM 320 325 52.6% 

21 T46 Caterpillar 3406 TA As Found 9/24/2009 RM 320 325 52.6% 21 T47 Caterpillar 3406 TA Mid Load, Low O2 9/24/2009 RM 320 325 68.3% 21 T48 Caterpillar 3406 TA Mid load, High O2 9/24/2009 RM 320 325 68.3% 21 T49 Caterpillar 3406 TA Low Load, High O2 9/24/2009 RM 320 325 52.6% 22 T50 Caterpillar G3406TA As Found - 1 hr Test 9/24/2009 RM 320 325 68.6% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-6 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

23 T51 Caterpillar G3406NA Low Load, Low O2 9/25/2009 RM 320 215 40.5% 23 T52 Caterpillar G3406NA Low Load, High O2 9/25/2009 RM 320 215 40.5% 23 T53 Caterpillar G3406NA High Load, High O2 9/25/2009 RM 320 215 66.5% 23 T54 Caterpillar G3406NA High Load, Low O2 9/25/2009 RM 320 215 66.5% 23 T55 Caterpillar G3406NA Mid Load, Low O2 9/25/2009 RM 320 215 60.5% 23 T56 Caterpillar G3406NA Mid Load, High O2 9/25/2009 RM 320 215 60.5% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-7 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

24 T57 Caterpillar 3406 NA Low O2 - 1 hr Test 9/25/2009 RM 320 215 96.8% 25 T58 Waukesha 1197 As Found - 1 hr Test 9/26/2009 RM 320 192 54.7% 25 T59 Waukesha 1197 High Load, Low O2 9/26/2009 RM 320 192 -- 26 T60 Caterpillar G3306NA Low O2 - 1 hr Test 9/26/2009 RM 320 145 45.2% 26 T61 Caterpillar G3306NA As Found 9/26/2009 RM 320 145 -- 27 T62 Caterpillar G3406TA Low O2 - 1 hr Test 9/28/2009 RM 320 325 95.2% 28 T63 Waukesha F1197 Low O2 - 1 hr Test 9/28/2009 RM 320 140 98.4% 29 T64 Caterpillar G3306NA As Found - 1 hr Test 9/28/2009 RM 320 145 52.8% 30 T65 Waukesha F1197G As Found - 1 hr Test 9/28/2009 RM 320 192 64.1% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-8 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

31 T66 Caterpillar G 3406TA As Found, Low O2 - 1 

hr Test

9/29/2009 RM 320 325 56.3% 

31 T67 Caterpillar G 3406TA High Load, Low O2 9/29/2009 RM 320 325 56.9% 31 T68 Caterpillar G 3406TA High Load, High O2 9/29/2009 RM 320 325 56.9% 31 T69 Caterpillar G 3406TA Low Load, High O2 9/29/2009 RM 320 325 41.5% 31 T70 Caterpillar G 3406TA Low Load, Low O2 9/29/2009 RM 320 325 41.5% 32 T71 Caterpillar 3406TA As Found 9/29/2009 RM 320 325 -- 32 T72 Caterpillar 3406TA As Found, High O2 - 1 

hr Test

9/29/2009 RM 320 325 53.3% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-9 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

33 T73 Caterpillar G3306NA Low O2 - 1 hr Test 9/29/2009 RM 320 145 61.3% 33 T74 Caterpillar G3306NA As Found 9/29/2009 RM 320 145 -- 34 T75 Waukesha F1197G As Found - 1 hr Test 9/30/2009 RM 320 192 67.2% 34 T76 Waukesha F1197G As Found, High O2 9/30/2009 RM 320 192 65.1% 34 T77 Waukesha F1197G Mid Load, Low O2 9/30/2009 RM 320 192 54.7% 34 T78 Waukesha F1197G Mid Load, High O2 9/30/2009 RM 320 192 54.2% 34 T79 Waukesha F1197G Low Load, Low O2 9/30/2009 RM 320 192 47.9% 34 T80 Waukesha F1197G Low Load, High O2 9/30/2009 RM 320 192 47.4% 35 T81 Caterpillar 3306 NA As Found 9/30/2009 RM 320 145 -- 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-10 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

35 T82 Caterpillar 3306 NA Low O2 - 1 hr Test 9/30/2009 RM 320 145 86.3% 36 T83 Caterpillar G3406NA Low O2, 1 hr Test 9/30/2009 RM 320 215 66.3% 36 T84 Caterpillar G3406NA As Found 9/30/2009 RM 320 215 -- 37 T85 Waukesha F1197G As Found 10/1/2009 RM 320 186 -- 37 T86 Waukesha F1197G Low O2, 1 hr Test 10/1/2009 RM 320 186 82.1% 38 T87 Waukesha F1197G As Found 10/1/2009 RM 320 192 54.2% 38 T88 Waukesha F1197G

As Found - Mid Load, 

Low O2 10/2/2009 RM 320 192 62.0% 

38 T89 Waukesha F1197G Mid Load, High O2 10/2/2009 RM 320 192 58.9% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-11 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

38 T90 Waukesha F1197G High Load, High O2 10/2/2009 RM 320 192 47.9% 38 T91 Waukesha F1197G High Load, Low O2 10/2/2009 RM 320 192 50.0% 38 T92 Waukesha F1197G Low Load, Low O2 10/2/2009 RM 320 192 42.7% 38 T93 Waukesha F1197G Low Load, High O2 10/2/2009 RM 320 192 44.8% 39 T94 Caterpillar G3406 NA As Found 10/5/2009 RM 320 215 94.2% 39 T95 Caterpillar G3406 NA Low O2 10/5/2009 RM 320 215 94.2% 40 T96 Caterpillar G3306TA As Found 10/5/2009 RM 320 203 57.9% 40 T97 Caterpillar G3306TA Low O2 10/5/2009 RM 320 203 57.9% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-12 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

41 T98 Caterpillar G3406TA Low Load, High O2 10/6/2009 RM 320 325 81.2% 41 T99 Caterpillar G3406TA Low Load, Low O2 10/6/2009 RM 320 325 81.2% 41 T100 Caterpillar G3406TA As Found, Low O2 10/6/2009 RM 320 325 93.5% 41 T101 Caterpillar G3406TA As Found, High O2 10/6/2009 RM 320 325 82.2% 42 T102 Caterpillar 3406 TA As Found 10/7/2009 RM 320 325 61.5% 43 T103 Caterpillar 3306 TA As Found, High O2 10/8/2009 RM 320 203 50.7% 43 T104 Caterpillar 3306 TA As Found, Low O2 10/8/2009 RM 320 203 51.7% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-13 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

43 T105 Caterpillar 3306 TA Mid Load, Low O2 10/8/2009 RM 320 203 45.8% 43 T106 Caterpillar 3306 TA Mid Load, High O2 10/8/2009 RM 320 203 45.8% 44 T107 Waukesha F1197GU As Found 10/9/2009 RM 320 192 68.8% 44 T108 Waukesha F1197GU As Found, High O2 10/9/2009 RM 320 192 68.8% 45 T109 Waukesha F-1197 G As Found 10/9/2009 RM 320 192 51.8% 45 T110 Waukesha F-1197 G As Found, Low O2 10/9/2009 RM 320 192 51.8% 46 T111 Waukesha F-817G As Found 10/9/2009 RM 320 132 24.6% 47 T112 Caterpillar 3306 NA As Found 10/10/2009 RM 320 145 91.1% 47 T113 Caterpillar 3306 NA As Found, Low O2 10/10/2009 RM 320 145 91.1% 48 T114 Caterpillar G3406 NA 10-Minute Pre-Run 10/7/2009 RM 320 215 100.0% 48 T115 Caterpillar G3406 NA One-Hour Pre-Catalyst 10/7/2009 RM 320 215 100.0% 49 T116 Caterpillar 3306 10-Minute Pre-Run 10/8/2009 RM 320 195 100.0% 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 A-14 

Engine No. Test No. Make Model Test Condition Test Date Test Method Rated HP LOAD

49 T117 Caterpillar 3306 One-Hour Pre-Catalyst 10/8/2009 RM 320 195 100.0% 50 T118 Cummins KTA 19GC 10-Minute Pre-Run 10/8/2009 RM 320 380 100.0% 50 T119 Cummins KTA 19GC One-Hour Pre-Catalyst 10/8/2009 RM 320 380 100.0% 

51 3 T120 Caterpillar G342-TA Pre-catalyst, 60 min March- April 2009 RM 323 250 68% 

NOTE1: Compressor suction discharge and suction pressures were not available for some engine tests (i.e., load not be calculated) NOTE2: ppmvd @ 15% O2 during best performing test for the engine NOTE3: Value in "CH2O" column is an average of 4 runs (i.e., 10 ppmvd, 8.5, 8.9, and 9.5) RM: EPA Reference Method 

Shaded cells indicate load data is based on post-test calibration of pressure gauges and fuel flow meters 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

APPENDIX B 

QA/QC PROCESS AND DATA REVIEW
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-1 Appendix B 

Appendix B: Data Review Process and Short Term Test Validation 

This appendix outlines the procedures used to ensure that reliable and accurate data were used in 

the MACT floor analysis. A test protocol (see Appendix C) was established prior to the 

emission measurement campaign to facilitate the collection of quality engine emissions data. In 

accordance with the test protocol, engine emission data collected for this project included 

formaldehyde, oxygen, and moisture. Engine design and operating data were also collected to 

document the engine operating conditions. All of this information was used to help determine 

the quality of information associated with engine tests and inform the decision to include the 

engine in the MACT floor analysis. 

Because emission data were provided by a variety of sources including EJC and numerous API 

member companies, a standard process to screen and access data quality was developed. This 

process included: 

• Preliminary screening – all test data were initially screened to determine if the tests complied 

with the basic project objectives. Section B.1 describes the engine test data screening 

process; 

• Emission test method QA checks – emission tests that passed the initial screening were then 

reviewed for compliance and consistency with the standard measurement methods. Sections 

B.2 and B.3 list the quality assurance activities and requirements for the measurement 

methods and summarize results for the MACT floor engines; 

• Engine operating data review - Section B.4 discusses the engine operating data collection, 

calibration of equipment for key process measurements, and calculation of engine efficiency 

parameters to evaluate engine load determinations. 

• Short test run data evaluation – to accommodate tests at additional operating conditions, 

some emission measurements were conducted for a period less than the standard one-hour 

performance test. Section B.5 discusses the validity of these shorter duration tests and 

statistically compares them to the standard (60-minute) tests. 

Engines with emission test data measured in compliance with the standard test methods and that 

had reliable engine operating data (i.e., engine load) were included in the MACT floor analysis. 

Conversely, engine data that was not determined of suitable quality, test duration, or under a 

reasonable engine operating condition were eliminated from the analysis and are not included in 

this report. 

B.1 Preliminary Engine Test Data Screening 

All test data were initially screened to determine if the tests complied with the primary project 

objectives. More specifically, the objective of the preliminary engine tests screening (i.e. prior to

more detailed data review and MACT floor analysis) was to eliminate engines and tests that did 

not meet the project data quality objectives and include only emission tests with sufficient data 

for QA checks and a representative measurement. The following discusses the parameters used 

to screen engine tests. 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-2 Appendix B 

• Insufficient QA Data and Test Documentation: Engines tests were not included in the MACT 

floor analyses because the quality assurance data associated with the tests was incomplete. 

• Insufficient Data Collection (non-representative measurement): Engine tests were rejected 

when they reported emissions after less than three (3) minutes of engine operation, an 

insufficient time to conduct a representative emission measurement. 

• Stable Engine Operation: Engine test data were collected or were invalidated during 

transient or unstable engine operations. As an example, an engine test would be eliminated if 

oxygen was above 2%. 

The data remaining after this screening process was considered appropriate for further evaluation 

and analysis. Test reports have been provided for all MACT floor engines and following a 

screening assessment were reviewed against the detailed Reference Method test requirements 

discussed below. 

B.2 CH2O Emissions by FTIR (EPA Method 320) 

EPA Method 320 quality assurance/quality control (QA/QC) requirements include pre- and post 

test Calibration Transfer Standard (CTS) calibrations and QA Spike Recoveries. The CTS 

calibrations are direct injection of the CTS calibration gas to the FTIR cell. The peak absorbance 

for the pre- and post-test CTS gas analyses must be within ±5 percent of the mean value. For 

these tests, the ASTM D 6348 requirement that the CTS gas analyses be within 5% of the 

certified value was also followed. The QA Spike Recovery requires that the calibration gas be 

spiked into the sample gas flow. Three independent spikes are conducted and the average 

recovery of the spiked gas should be within 0.7 to 1.3 times the expected concentration. Table 

B-1 summarizes the reported Method 320 QA/QC data for the MACT floor engines. 

Table B-1. EPA Method 320 Method Performance for MACT Floor Engines 

MACT Floor 

Engine ID

Engine 

Make/Model

Pre-Test 

CTS

Post-Test 

CTS

QA Spike 

Recovery

Test 

Status

Acceptance Criteria = +/- 5% of CTS Cal Gas 70 – 130%

17 Waukesha F1197GU 1.8% 1.3% 103% Pass

43 Caterpillar 3306 TA 1.2% 2.2% 84% Pass

21 Caterpillar 3406 TA - 0.1 1.7% 112% Pass

5 Caterpillar G-342TA 1.4% -1.2% 93% Pass

14 Waukesha F1197GU 0.5% 1.7% 123% Pass

34 Waukesha F1197G 2.9% 4.9% 98% Pass

38 Waukesha F1197G 1.6% 3.3% 95% Pass

B.3 Oxygen Emissions by EPA Method 3A and ASTM Method 6522 

Oxygen emissions were measured using EPA Method 3A and ASTM Method 6522 for portable 

analyzers. The daily QA/QC activities and method performance requirements for Method 3A 

include: 

• Pre-Test Measurement System Performance Tests 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-3 Appendix B 

- Calibration Error Test. The low-, mid-, and high-level calibration gases are sequentially 

introduced directly to the analyzer. The analyzer calibration error is calculated for the 

three levels as the difference between the analyzer reading and the calibrated gas value 

divided by the calibration span. Method Performance specification is + 2% of calibration 

span. An alternative specification, difference between the analyzer reading and the 

calibrated gas value < 0.5 %, can be used for low concentration measurements. 

- System Bias Check. An upscale gas (mid- or high-level) and then a low/zero gas are 

introduced at the probe upstream of all sample conditioning components. The system 

bias is calculated as the difference between the analyzer reading during the direct 

calibration and during the system bias divided by the calibration span. Method 

Performance specification is + 5% of calibration span. An alternative specification, 

difference between the analyzer reading during the direct calibration and during the 

system bias < 0.5 %, can be used for low concentration measurements. 

• Interference Check. Potentially interfering gases (e.g. CO2) are introduced to the 

analyzer. The total interference response must not be greater than 2.50 percent of the 

calibration span for the analyzer tested. 

• Post-Run System Bias Check & Drift Assessment, 

- System Bias Check. As discussed above. 

- Drift Check. Low-level and upscale drift is calculated as the difference between the pretest and post-test System Bias Check values. Method Performance specification is + 3%. 

An alternative specification, difference between the pre-test and post-test System Bias 

Check values < 0.5 %, can be used for low concentration measurements. 

The QA/QC activities and method performance requirements for ASTM 6522 include: 

• Equipment Preparation Measurement System Performance Tests 

- Linearity Check. A linearity check is performed for each electrochemical cell by injecting 

the zero and mid- and high-level calibration gases to the analyzer. Method Performance 

specification is < 2.5% of calibration gas concentration. These checks are repeated 

whenever a cell is replaced. 

- Interference Check. An interference check is required for the CO electrochemical cell. 

Method Performance specification is that interference responses must be < 5% of the 

average stack gas concentration for each test run. 

- Stability Check. The stability check is performed for each electrochemical cell by 

injecting calibration gas for a 30 minute period. Method Performance specification is 

that the difference between the lowest and highest one-minute averages must be < 2.0% 

of the calibration gas concentration. These checks are repeated whenever a cell is 

replaced or exposed to greater than 125% of the highest calibration gas concentration. 

• Pre-test Measurement System Performance Tests 

- Calibration Error Check. The zero and span calibration gases are sequentially introduced 

to the analyzer at the probe tip. The Method Performance specification for the zero gas is 

< 3% of the calibration gas concentration for CO and < 0.3% O2 for the O2 cell. The 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-4 Appendix B 

Method Performance specification for the span gas is < 5% of the calibration gas 

concentration for CO and < 0.5% O2 for the O2 cell. 

• Post-test Measurement System Performance Tests 

- Calibration Error Check. The zero and span calibration gases are sequentially introduced 

to the analyzer at the probe tip. The Method Performance specification for the zero gas is 

< 3% of the calibration gas concentration for CO and < 0.3% O2 for the O2 cell. The 

Method Performance specification for the span gas is < 5% of the calibration gas 

concentration for CO and < 0.5% O2 for the O2 cell. 

- Interference Verification. Calculate the CO interference response based on the post-test 

calibration data and average emission concentration for the test. Method Performance 

specification is that interference responses must be < 5% of the average stack gas 

concentration for each test run. 

For all the MACT floor engines, method performance requirements were achieved for the 

emission measurements. 

B.4 Engine Design and Operating Data 

For the EJC testing, engine design information were provided by the operators prior to test 

mobilization and then verified on-site. These data included engine make and model, site-rated 

horsepower, and compressor make, model, number of stages, and stage characteristics. Engine 

operating parameters were monitored during the testing to estimate engine operating load. These 

parameters included compressor suction and discharge gas pressures and temperatures, fuel gas 

flow rate, and engine speed. Compressor manufacturer software was used to estimate the 

compressor load and parasitic power requirements (e.g., pumps, alternator, and fans) were 

estimated from the engine speed and engine manufacturer specifications. 

Process monitoring equipment was calibrated. Compressor suction and discharge pressures were 

typically measured by engine control panel pressure gauges. These panel gauges were then 

calibrated against a reference pressure gauge and test data were adjusted accordingly. 

Compressor temperatures were typically measured with a panel meter and a second temperature 

measurement by an IR meter or thermocouple was conducted to verify the measurement. Fuel 

gas flow rate was measured using rotary gas meters. These meters measure actual gas volume 

and thus require gas pressure and temperature measurements to determine fuel flow at standard 

pressure and temperature. Post test calibrations of the rotary flow meters and pressure gauges 

were conducted and measurement data adjusted accordingly. 

QA/QC activities also included calculation of engine brake-specific fuel consumption (BSFC) 

based on measurements of fuel use and engine load. BSFC is calculated as British thermal units 

per horsepower hour (Btu/hp-hr) and is a measure of engine efficiency. BSFC is impacted by 

numerous parameters - including engine design, load, age, maintenance practices and schedule, 

fuel properties and ambient conditions - and can range considerably, especially at lower loads for 

older engines. For 4SRB engines less than 500 hp, BSFC typically ranges from 7,500 to greater 

than 12,000 Btu/hp-hr. Table B-2 summarizes key operational data for the MACT Floor engines 

including BSFC. With the exception of two engines, BSFC values were generally within the 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-5 Appendix B 

expected range and provided confidence in the engine load determinations. For engines with 

calculated BSFC values outside the typical range, the fuel flow and engine load measurement 

data were further examined. Two 4SRB MACT Floor engines, engine nos. 34 and 38, had 

BSFCs below the expected range for numerous operating conditions. These were both 

Waukesha F1197G engines. Post-test calibration of the fuel gas pressure gauge used during the 

testing of these two engines determined that the gauge was damaged, and the fuel pressure and 

fuel flow measurements were likely erroneous. A comparison of the fuel pressures measured 

during these MACT Floor engine tests with fuel pressures measured for other Waukesha F1197G 

engines in the area indicated that the MACT Floor engines fuel pressures and fuel flows were 

likely biased low. In addition, recalculation of the MACT Floor engines BSFC using fuel 

pressures measured on other Waukesha F1197G engines produced BSFC values in the expected 

range; thus, it was concluded the measured fuel flows were biased low and the engine load 

measurements were reliable. As discussed in the body of the report, numerous parameters are 

expected to impact formaldehyde emissions from 4SRB engines including load, fuel quality, 

excess air, engine age and maintenance practices/schedule, elevation, and ambient 

conditions. While the project attempted to test engines over their as-found operating envelope, 

the testing was not designed to be a parametric investigation and a quantified evaluation of the 

individual parameters impacting CH2O emissions was well beyond the scope of this testing 

project; thus, it would not be appropriate to attempt to quantitatively correlate the CH2O 

emissions data to the operating data in Table B-2. However, an inspection of the data generally 

shows CH2O emissions increasing with lower load and higher excess air. 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 B-6 

Table B-2. MACT Floor Engines Operating Data. 

Unit ID 

Number 

 Engine 

Manufacturer 

 Engine 

Model Operating Condition Fuel LHV (Btu/SCF) BSFC (Btu/hp*hr) OEM Max Horsepower (hp) Engine Speed (RPM) Brake Horsepowe

(hp) 

Caterpillar 3306 TA As Found, High O2 926 7,534 203 1,646 103 Caterpillar 3306 TA As Found, Low O2 926 8,188 203 1,649 105 Caterpillar 3306 TA Mid Load, High O2 926 9,636 203 1,632 93 

43 

Caterpillar 3306 TA Mid Load, Low O2 926 8,933 203 1,126 93 

Waukesha F1197GU As Found - 1 hr Test 927 12,851 192 1,156 76 Waukesha F1197GU As Found - Retest 927 8,520 192 1,215 107 Waukesha F1197GU As Found, Low O2 927 11,019 192 1,215 107 Waukesha F1197GU High Load, High O2 927 9,452 192 1,245 122 Waukesha F1197GU High Load, Low O2 927 9,682 192 1,245 122 Waukesha F1197GU Low Load, High O2 927 9,069 192 1,200 80 

14 

Waukesha F1197GU Low Load, Low O2 927 9,529 192 1,200 80 

Waukesha F1197G As Found 1,006 6,597 192 1,310 104 Waukesha F1197G As Found - Mid Load, Low O2 1,006 6,385 192 1,311 119 Waukesha F1197G High Load, High O2 1,006 5,700 192 1,017 92 Waukesha F1197G High Load, Low O2 1,006 6,488 192 1,075 96 Waukesha F1197G Low Load, High O2 1,006 5,816 192 1,097 86 Waukesha F1197G Low Load, Low O2 1,006 7,458 192 1,046 82 

38 

Waukesha F1197G Mid Load, High O2 1,006 5,644 192 1,294 113 

Waukesha F1197GU As Found - 1 hr Test 1,023 12,851 192 975 69 

17 Waukesha F1197GU As Found, High O2 1,023 10,899 192 -- 69 

Waukesha F1197GU Mid Load 1,023 11,918 192 1,125 103 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 B-7 

Table B-2 MACT Floor Engines Operating Data (Cont).

 Unit ID 

Number 

 Engine 

Manufacturer 

 Engine 

Model Operating Condition Fuel LHV (Btu/SCF) BSFC (Btu/hp*hr) OEM Max Horsepower (hp) Engine Speed (RPM) Brak

Horsep

(hp

Waukesha F1197G As Found - 1 hr Test 967 4,229 192 1,320 129 Waukesha F1197G As Found, High O2 967 4,775 192 1,313 125 Waukesha F1197G Low Load, High O2 967 4,722 192 1,355 91 Waukesha F1197G Low Load, Low O2 967 4,931 192 1,372 92 Waukesha F1197G Mid Load, High O2 967 4,744 192 1,340 104 

34 

Waukesha F1197G Mid Load, Low O2 967 4,640 192 1,352 105 

Caterpillar G-342TA As Found - 1 hr Test 1,084 7,473 265 1,000 188 Caterpillar G-342TA As Found, Low O2 1,084 8,377 265 1,100 168 Caterpillar G-342TA High Load, High O2 1,084 8,192 265 1,100 195 Caterpillar G-342TA High Load, Low O2 1,084 8,834 265 1,100 195 Caterpillar G-342TA Low Load, High O2 1,084 8,935 265 1,025 100 

5 

Caterpillar G-342TA Low Load, Low O2 1,084 10,867 265 1,025 100 

Caterpillar 3406 TA As Found 1,004 9,460 325 -- 171 Caterpillar 3406 TA Low Load, High O2 1,004 8,003 325 -- 171 Caterpillar 3406 TA Low Load, Low O2, 1 hr 1,004 9,217 325 1,788 171 Caterpillar 3406 TA Mid load, High O2 1,004 6,644 325 1,775 222 

21 

Caterpillar 3406 TA Mid Load, Low O2 1,004 7,422 325 1,775 222 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

March 2010 

B-8 Appendix B 

B.5 Validity of Shorter Test Runs Data 

Sixty minute test runs are typically conducted for compliance test measurements. This time 

period is partially a remnant of compliance tests conducted using integrated grab samples with 

subsequent, off-site analysis; for these tests, sixty minute (or longer) testing is required to ensure

source operating and emission variability was captured and a representative sample was 

collected. Emission variability can be caused by normal process cycling (e.g. caused by the 

process control system or inherent to a continuous batch process such as an incinerator where 

waste is periodically charged) or instability (e.g. caused by changing process inputs or inherent 

equipment operating characteristics). FTIR provides real-time measurements; thus, it is possible 

to observe if the source emissions are varying or if the source is operating at a stable, steady-state

condition. If emissions are stable, then a representative measurement can be conducted in a 

relatively short time; that is, a sixty minute sample period is not needed for a representative 

measurement. Conversely, if emissions are observed to vary, then a longer measurement would 

be required to encompass the emission variability and provide a representative average 

measurement. 

The engines tested for this program generally operated at steady state conditions during the 

emission testing. Engine operators were present during the testing to minimize testing delays 

and the engine settings and the process (i.e., gas well production) were monitored for stable 

operation. The minute-to-minute FTIR formaldehyde measurements confirmed the stable engine 

operation. Because engine operations and emissions were essentially invariant, it was possible to 

conduct shorter test runs for some engine operating conditions. The shorter test runs were used 

because project time and resources were constrained. An emphasis was placed on quickly 

identifying candidate MACT floor engines and collecting variability test data over a range of 

expected operating conditions as opposed to spending limited resources gathering data from the 

lower 88 percentile units. FTIR testing on each engine was typically limited to one day or less; 

thus, shorter test runs optimized the project resources (FTIR test day) and produced a larger and 

more variable (i.e., more representative) data set for MACT floor analysis. 

Based on the observed FTIR minute-to-minute formaldehyde measurements, a ten-minute test 

period was selected for some operating conditions. As noted above, the CH2O emissions were 

essentially invariant over the ten-minute period and FTIR data logger observations indicated a 

representative sample was measured. FTIR spectrometer interferograms consisting of 28 coadded scans were recorded continuously during the test periods, and provided approximately 30-

second average concentrations. These values are then averaged in 2 blocks and reported once 

per minute to the data logger; thus, for a 10-minute test, a total of 20 samples were effectively 

collected. 

As discussed above, collecting a representative sample requires that any emissions cycling or 

variability be encompassed by the sample period. In addition to the ten-minute tests, at least 

two sixty-minute tests were conducted on each MACT Floor engine. Table B-3 compares the 

relative standard deviations for the 10- and 60-minute tests for the MACT floor engines. Test run 

standard deviations were calculated using each one-minute average as a single data point within 

a test (i.e., 10 data points within a 10-minute test). The relative standard deviation (RSD) is 

expressed as percentage: 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-9 Appendix B 

RSD = 100 x Standard Deviation of Sample Points / Mean of Sample Points 

Smaller RSDs indicate that the data are closer to the mean (i.e., data have lower variance) than 

larger RSDs. If the 10-minute sample period was not sufficient to encompass engine emission 

variability or cycling, then the RSDs would be expected to be much larger for the 10-minute tests 

than the 60-minute tests. Inspection of the RSD data in Table B-3 shows that this did not occur. 

Ten-minute test RSDs are generally comparable or lower than the sixty-minute test RSDs When 

viewed as an overall group of tests, the average RSD for the 10-minute tests is 5.9% and is lower 

than the RSD for the 60-minute tests (6.9%). In addition, no 10-minute test had an RSD value 

greater than 10%, while four (4) separate 60-minute tests had RSDs greater than 10%, and the 

range of RSDs for 10-minute tests is smaller (1.2% to 9.9%) than the range for 60-minute tests 

(2.8% to 14.4%). 

In summary, the observed steady emissions (i.e., no cycling or upward or downward trends) 

during the ten-minute tests and the comparable RSDs for the 10- and 60-minute tests CH2O 

measurements indicate that the 10-minute measurements were representative of the engine 

operating condition during the test. Therefore, the short-term test data have been retained for the 

purpose of assessing emissions variability from the MACT floor engines. 
Technical Report: 4SRB Natural Gas-Fired Engine Emissions Data for MACT Floor 

April 2010 

B-10 Appendix B 

Table B-3. Comparison of Standard Deviations for Short-Term and Long-Term Tests.

Test 

No. CH2O

1 Standard 

Deviation RSD RSD Standard Deviation CH2O

1 Test 

No. Engine 

ID 

60-Minute Tests 10-Minute Tests

43 T15 3.53 0.51 14.4% 5.6% 0.48 8.64 T13 

43 T16 7.37 0.57 7.7% 5.4% 0.18 3.31 T14 

14 T23 5.32 0.52 9.8% 3.5% 0.27 7.73 T24 

14 T25 5.02 0.53 10.6% 2.8% 0.13 4.72 T26 

14 T27 9.42 0.41 4.4% 4.6% 0.25 5.49 T29 

14 T28 8.29 0.42 5.1% 

38 T88 4.96 0.43 8.7% 5.2% 0.35 6.68 T87 

38 T90 7.92 0.34 4.3% 3.7% 0.23 6.29 T89 

38 T93 7.24 0.37 5.1% 9.9% 0.53 5.36 T91 

38 9.5% 0.49 5.15 T92 

17 T36 3.31 0.27 8.2% 8.7% 0.66 7.59 T37 

17 T38 3.18 0.37 11.6% 

34 T75 4.94 0.54 10.9% 1.2% 0.09 7.57 T76 

34 T77 6.84 0.29 4.2% 2.3% 0.12 5.31 T79 

34 T78 7.6 0.21 2.8% 

34 T80 7.71 0.22 2.9% 

5 T9 4.71 0.17 3.6% 4.2% 0.22 5.21 T11 

5 T10 6.12 0.43 7.0% 9.7% 0.92 9.52 T14 

5 T12 9.24 0.37 4.0% 

5 T13 12.1 0.74 6.1% 

21 T45 3.74 0.30 8.0% 5.6% 0.61 10.94 T46 

21 T47 3.53 0.16 4.5% 9.8% 0.83 8.43 T48 

21 9.4% 0.91 9.65 T49 

NOTE1: ppmvd @ 15%O2 
Technical Report: Natural Gas-Fired Engine Emissions Data for MACT Floor 

March 2010 

APPENDIX C 

FORMALDEHYDE EMISSIONS MEASUREMENT 

TEST PROTOCOL 
40 CFR 63 Subpart ZZZZ 

Natural Gas Fired Engine MACT Floor Test Plan 

& 

Equipment / Operations Information Gathering 

PREPARED FOR: 

Stephanie Meadows 

Upstream Senior Policy Analyst 

American Petroleum Institute 

1220 L Street, NW 

Washington, D.C. 20005 

PREPARED BY: 

innovative environmental solutions, inc. 

P.O. Box 177 

Cary, IL 60013-0177 

September 30, 2009 Version 1 
October 2, 2009 

Final Draft Test Plan 

1 

MACT Floor Test Program Background and Objectives

The March 2009 proposed revisions to the Federal National Emission Standards for Hazardous Air 

Pollutants (NESHAP) for reciprocating internal combustion (IC) engines (74 FR 9698) include 

emission standards based on insufficient and technically flawed emissions data. The resulting paucity

of data are not sufficient to complete a MACT floor analysis or representative of the affected engine 

populations. Flaws in the existing data include emission test methods with known negative biases and 

inappropriate engine operation during the testing. Based on industry comments, EPA has 

acknowledged that additional emissions data and analysis is needed to define emission limits for the 

Final Rule. To address the data deficiency and inform the MACT floor analysis, API and a consortium 

of engine rental companies are coordinating an emission test project on existing reciprocating internal 

combustion engines at oil and gas (O&G) facilities. This document identifies the Test Plan for that 

project to ensure accepted and consistent methods are used for the testing. The test results will be 

integrated into a single emissions test report at the completion of the test program. 

For major source engines and most area source engines, the Proposed Rule includes emission limits. 

The emission limits are based on the “MACT floor”, and the technology basis is an “uncontrolled” 

engine. In some cases, the emission limit is the MACT floor emission level, while in other cases EPA 

assumed that “above the floor” catalytic control is warranted and based the emission limit on the floor 

level less a 90% reduction from catalytic control. These emission limits will not be achievable by the 

vast majority of uncontrolled existing engines; that is, for an uncontrolled unit to meet the emission

level associated with the “best performing” MACT floor limit, catalytic control will be required for 

nearly all units. Refer to API Comments 5.1 and 6.2 for additional detail. 

This test program is designed to obtain uncontrolled “as found” emission data to support revisions to 

the MACT floor limits in the upcoming Final Rule that will amend the NESHAP for reciprocating IC 

engines 40 CFR, Part 63, Subpart ZZZZ. Data collected as part of this intensive effort are needed to 

develop technically defensible emission standards. 

The MACT floor emissions test project objectives include: 

3. Establish a test program to consistently obtain emission data for developing MACT floor 

emission limits that address the size, type, and operation of affected engines. The focus of the 

MACT floor testing program is primarily directed toward smaller natural gas fired engines 

(< 500hp). 

4. Obtain operational variability data from engines that are expected to be in the MACT floor data 

set (i.e. engines in the best performing 12 percent of engines in each category/subcategory) to 

allow determination of emission limits that include normal operational variability. Variability 

parameters may include: 

• Excess O2 from 4SRB; 

• Percent load; 

• Multiple engines of identical make / model; 

• Fuel quality; and, 

• Ambient affects including temperature, relative humidity, & elevation. 
October 2, 2009 

Final Draft Test Plan 

2 

 

Variability is an important consideration because it allows consideration of operating factors 

when establishing the MACT floor emission limit. Thus, these data are a key component of the 

test program. For example, when establishing the standard, our understanding is that EPA is 

not required to use an average of the best performing twelve percent of units as the MACT 

floor emission limit. Rather, EPA has the latitude to select the limits at the worst reasonable 

condition for the best controlled similar unit. [“EPA would be justified in setting the floors at

a level that is a reasonable estimate of the performance of the ‘best controlled similar unit’ 

under the worst reasonably foreseeable circumstances.” Sierra Club v. EPA, 167 F.3d 658 

(D.C. Cir. 1999)]. 

In addition, in Mossville Environmental Action Now v. EPA, 370 F.3d 1232 (D.C. Cir. 2004), 

the Court held that floors may legitimately account for variability because “each [source] must 

meet the [specified] standard every day and under all operating conditions.” Thus, emission 

variability can be considered in setting emission limits, and MACT floor emission limit can be 

based on the highest emissions for MACT floor engines considering operational variation. 

Table 1 presents a draft test matrix template for the primary engine categories. The engine category 

priorities discussed in this plan are based upon the RICE fleet used by natural gas production and 

gathering facilities and test data reviewed in the RICE NESHAP proposal. As testing commitments, 

locations, schedules, and engine types are finalized, Table 1 will be completed as a stand alone 

supplementary document that identifies engine makes/models and counts. At present, industry and 

trade associations anticipate on the order of 100 tests will be completed over a range of engine types, 

sizes, and operating conditions. 

Additional subcategories or further refinement of the horsepower ranges can be completed based on 

participant direction and engine types available for testing. Since the MACT floor is based on an 

uncontrolled engine, NSCR and oxidation catalyst equipped engines are not preferred for the purpose 

of establishing the MACT floor. Should controlled engines be included in the measurement program, 

pre-catalyst testing is recommended. In addition, proper consideration of air fuel ratio (AFR) system 

test impacts should be made. Potential test considerations includes disconnecting the AFR and 

reverting to manual adjustments or AFR system bypass (see 4SRB O2 considerations below). 

Similar to the proposed draft test matrix, Table 2 presents a table to summarize emissions data that is 

compiled from previously completed tests (i.e., available test results from O&G companies). These 

data may be used to establish or confirm MACT floor emission limits or further the understanding of 

emissions variability. These data are expected to be very limited for smaller burn engines (i.e., where 

formaldehyde is needed) and primarily encompass larger lean burn units. 
October 2, 2009 

Final Draft Test Plan 

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Table 1. Test Matrix and Test Engine Count (MACT floor basis is 12% of the engines test

Size Category 

 (HP) 

Number of 

4SRB 

Engines 

Number of 

2SLB 

Engines 

Number of 

4SLB 

Engines 

Su

50-100 hp 

MACT Floor Engine Count X X X 

100-250 hp 

MACT Floor Engine Count X X X 

250-500 hp e.g. ...5 (Ajax DPC 280) 

MACT Floor Engine Count X X X 

>500 hp 

Total X Y Z 
October 2, 2009 

Final Draft Test Plan 

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Table 2. Existing Test Data to Support MACT Floor Determination 

Size Category 

 (HP) 

Number of 

4SRB 

Engines 

Number of 

2SLB 

Engines 

Number of 

4SLB 

Engines 

Su

50-100 hp 

MACT Floor Engine Count X X X 

100-250 hp 

MACT Floor Engine Count X X X 

250-500 hp 

MACT Floor Engine Count X X X 

>500 hp e.g. ...1 - (Clark TLA-6) 

Total X Y Z 
October 2, 2009 

Final Draft Test Plan 

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Reference Test Methods and Procedures

Testing should be conducted in accordance with EPA/ASTM reference test methods and 

procedures; however, due to time constraints and limited resources, data will typically not be 

specifically conform to performance or compliance test criteria (e.g., three one-hour tests are not

recommended for the purpose of gathering MACT floor engine performance data on multiple units 

when continuous test method (e.g., FTIR) is used). Because these data will be submitted to EPA for 

regulatory development, adherence to the test methods is necessary. Any exceptions or deviations 

to the reference method procedures must be documented to assess the appropriateness, quality, 

adequacy, and representativeness of the emission data. 

The testing will include a single one hour test on an “as-found” engine (i.e. no adjustment to the 

engine will be made – excluding 4SRB O2 exhaust levels as discussed below). For units identified 

as MACT Floor engines, subsequent tests at varied load conditions, possible varied ambient 

condition (e.g. early morning vs. mid-day operation), and, for 4SRB units, varied exhaust O2 levels 

should be conducted to gather data that characterizes emissions variability. 

Preferred Test Methods and Notes

• Although Fourier Transform Infrared spectroscopy (FTIR) – [EPA Method 320 or ASTM 

D6348] is more costly and resource intensive than the alternative Method 323 acetylacetone 

method, it provides near real time measurements and flexibility for assessing formaldehyde 

emissions from rich burn MACT floor candidate units. Alternatives to FTIR are discussed 

below. FTIR species include: 

- CO 

- CO2

- NO and NO2 

- Formaldehyde 

- C1 – C6 speciated hydrocarbons (e.g., to determine VOCs) 

- Ammonia 

- Moisture 

FTIR provides near real time instrument response and the ability to judge test results (e.g., 

whether the unit is a MACT floor engine). One-minute average data should be logged and 

archived for all FTIR measured compounds. If Method 323 formaldehyde data are obtained, 

care must be taken to ensure that sample flow rates are within the prescribed range (0.2 to 0.4 

liters per minute) and three one hour test runs are required. A potential list of FTIR testing 

companies is provided as Attachment 2. 

• O2 and CO2 by instrumentation – [EPA Method 3A] - Determination of Oxygen and Carbon 

Dioxide Concentrations in Emissions from Stationary Sources (Instrumental Analyzer 

Procedure)] or portable analyzer [ASTM D6522-00]; 

• Moisture by FTIR or impingers [EPA Method 4]; 
October 2, 2009 

Final Draft Test Plan 

6 

• Exhaust gas flowrate by F-factor [EPA Method 19]; 

• Sample Ports and Location [EPA Method 1 or 1A]. Two sample ports should be located at 90 

degrees apart and at least two, and ideally eight, stack or duct diameters downstream from and 

at least one half, and ideally two, diameters upstream of any process change or exhaust to 

atmosphere. One port will be used for a thermocouple measurement and the second for the 

heated FTIR sample probe. 

• For 2SLB and 4SLB engines, the NESHAP emission limits are based on the surrogate 

compound CO and a simplified gas measurement approach can be used. CO, NOx and O2 can 

be measured using [ASTM D6522] - Determination of Nitrogen Oxides, Carbon Monoxide, and 

Oxygen Concentrations in Emissions from Natural Gas-Fired Reciprocating Engines, 

Combustion Turbines, Boilers, and Process Heaters Using Portable Analyzers

Quality Assurance / Quality Control

All testing should be conducted in adherence with the reference test methods. Method deviations 

should be documented and explained (e.g. sample port location). Because formaldehyde is highly 

water soluble, sample line temperature maintenance is required to avoid moisture condensation. 

Recommended additional procedures to ensure data quality include: 

• Low concentration O2 calibration gases for measuring oxygen in rich burn engines exhaust. 

From EPA Method 7E/3A “to the extent possible, the measured emissions should be between 20 

to 100 percent of the selected calibration span.” Thus, to measure 0.5% O2, the calibrated range 

should be about 0 – 2%. 

• Similarly, a range of CO2 calibration gases will be required to measure CO2 from both rich burn 

and lean burn engines. 

• QA Spikes for the FTIR systems are recommended for each engine using formaldehyde and the 

spiking compound. Stack gas formaldehyde concentrations should be measured immediately 

before and after the QA spike. 

• CO2 measurements by both continuous analyzer (EPA Method 3A) and by FTIR can be used to 

gauge the uncertainty in the FTIR emission measurements. 

• The operator must identify the test load and report the basis for determining the operating load 

for the test. 

Reporting

Emissions should be reported in units of ppmvd, ppmvd @ 15% O2, lb/hr, and g/hp-hr. Test reports 

should be provided to IES to facilitate review and validation of MACT floor units. Multiple test 

reports are not required for test campaigns on multiple engines. A single summary report is 

preferred. 
October 2, 2009 

Final Draft Test Plan 

7 

Additional Test Considerations

Engines should be tested “as found”, and engine operation should not be altered or adjusted prior to 

initial testing other than to adjust the “baseline O2” for 4SRB engines as discussed below. 

Operating conditions should be logged (see Attachment 1). Engine exhaust temperature should be 

monitored for the duration of all tests. For 4SRB engines, emissions are dependent on the amount 

of excess oxygen (i.e., related to the air-to-fuel ratio). Thus, 

Four-stroke rich burn engine considerations: 

• If the “as-found” excess O2 is higher than 0.5%, then a short term test will be completed 

before adjusting to a “baseline O2 level”. In this case, test the 4SRB for approximately 10 

minutes at the "as found" oxygen measured value and record the data. Stable operation of 

the engine over this timeframe can be documented based on 1-minute test data. 

• Baseline O2 level: If the as found excess O2 is greater than 0.5%, after the step above is 

completed adjust the fuel regulator or carburetor setting to obtain an exhaust O2

concentration of approximately 0.5% or lower (baseline test condition for 4SRB engines). 

The manual adjustment is necessary because these engines are unsophisticated and do not 

include active control of excess air. Complete a one hour test at this condition. This test 

point is likely to be the “best performing level” for that particular test condition (i.e., load, 

ambient conditions, etc.). If exhaust oxygen is at 0.5% or lower "as found", the one hour 

test will be completed at the as found condition. As found units greater than 0.5% O2 are 

unlikely to be MACT floor engines – thus the excess air adjust will provide more valuable 

data for the analysis and the range of “as found” O2 levels is also pertinent information. 

• Subsequent fuel pressure adjustments or carburetor settings (e.g. for variability testing) 

should result in exhaust O2 concentrations less than 2 percent for consistency with the EPA 

definition of a rich burn engine. The “as found” conditions should be documented as 

indicated above. 

 

Two- and four-stroke lean burn engine considerations: 

• CO as surrogate for lean burn engines; 

• O2 calibrations should be within the expected range of operation (e.g. approximately 10 to 

18 % O2). 

Variability Testing

If a particular engine appears to be a candidate “MACT floor” engine (i.e., within the best 

performing 12% based on the number of engines in the test program), then additional testing will be 

completed on that engine. These tests will vary the excess O2 level (via carburetor or fuel pressure 

adjustment) over multiple test points and also vary load, as feasible. If the “as found” test was at 

reduced load, load adjustment to a higher load will be attempted. Lower load tests will also be 

attempted. Multiple excess O2 levels will be tested at each load. The number of data points to 

conduct this testing introduces test timing issues, because there is not time or resources available to 

spend multiple days testing a single engines. Thus, abbreviated run times will be used for most test 
October 2, 2009 

Final Draft Test Plan 

8 

conditions – i.e., ten minutes of FTIR data with stable operation and emissions stability ensured for 

that period. 

1. Excess O2 from 4SRB – Measure emissions for MACT floor units to establish emission 

range. Simplest matrix could be lowest excess O2 (nominally 0.5% or lower) and ~2% 

excess O2. Additional excess air and load conditions could be tested as time permits. 

2. Percent Load – Engine load can be changed by adjusting the suction, restricting the 

discharge, and/or changing the bypass valves. Target test loads are 50%, 75%, and 100% of 

maximum achievable load. These load levels are pertinent because the “maximum 

achievable” load in practice for production engines will often be less than the rated load. 

When load is changed to a different test condition, obtain a ten minute test run for most 

excess O2 tests, with the 0.5% excess O2 test and interim excess O2 test runs lasting 10 

minutes. For each load, the higher excess O2 test run at 2% O2 will acquire one hour of data. 

The higher O2 test condition may bound the upper end of the emissions variability range, so 

a one hour test run is proposed for these tests. These data should provide insight on 

formaldehyde variability for “MACT floor” 4SRB engines. Test data should be continuously 

recorded during load transitions. 

3. Identical Make / Model – Document information on identical or “similar” MACT floor 

units. “Location-based” issues that may affect emissions such as altitude and ambient 

temperature may need to consider data from an engine that is the same make and model as 

MACT floor engines. (For example, MACT floor data in Texas; altitude and temperature 

data may be available for an identical engine in New Mexico or Colorado.) 

4. Fuel Variability – Obtain and document fuel analyses for evaluating effect on emissions. 

5. Ambient parameters temperature, barometric pressure, relative humidity, and altitude – 

should be documented during testing for evaluating the effect on emissions 

6. Other 

The dataset will be reviewed to evaluate whether ambient effects can be discerned. Depending 

upon that review, it may be necessary to consider data from engines that are not MACT floor units, 

but identical make and model to MACT floor units, to assess variability from external 

environmental factors. Fuel analysis records will be collected and the data analyzed to assess 

potential impacts of varied fuel quality on emissions. 

Schedule 

Pending a potential extension request, EPA has requested all supporting MACT floor data by the 

end of October. Industry responses on test engines completing Table 1 and available test reports for 

Table 2 should be accompanied with tentative schedule(s) for completing the test or providing the 

data.
October 2, 2009 

Final Draft Test Plan 

9 

Attachment 1 

Supplemental Engine Data 

In addition to the source test report, the following information will assist in the determination of 

whether an engine is a “best performing 12 percent MACT floor engine” [Clean Air Act mandated 

target from §112(d)(2)]. All emissions data should be reported as ppmvd @ 15% O2. 
October 2, 2009 

Final Draft Test Plan 

10 

Required Supplemental Information 

Company

Contact Name __________ email address __________ Phone number __________ 

Engine and Driven Equipment

Engine Make __________ Engine Model ___________ Installation Date __________ 

Engine serial number or unique identifier __________________________________________ 

Engine Age ________________________ 

Nameplate hp _________________ Site Rated hp __________ 

Circle One 4SRB 2SLB 4SLB 

Location _________________________________ Elevation __________(feet above sea level) 

Pollution Controls Y / N Description (including make and model): _____________ 

______________________________________________________________________________ 

Ignition system _______________ (e.g. Altronic) 

Engine condition upon arrival: __________________________________________________ 

Date and description of last preventative maintenance: _______________________________ 

Maintenance interval and description: _____________________________________________ 

Engine life cycle (overhaul interval (yr) remaining life of overhaul (yr)) _________________ 

Aftermarket AFR __________ As Found Setting __________ 

Driven Equipment

Make __________ Model ___________ 

Compressor Cylinder Bore __________ Stroke __________ 

Generator Rating __________ 

Test Conditions & Murphy Panel Data

Percent Load __________ including parasitic hp __________ 

Description of how load was determined: ____________________________________________ 

________________________________________________________________________________

________________________________________________________________________________ 

RPM __________ Suction Pressure __________ Suction Temperature __________ 
October 2, 2009 

Final Draft Test Plan 

11 

Discharge Pressure __________ Discharge Temperature __________ 

Manifold Temperature __________ Pressure __________

Water Jacket Temperature __________ Compressor VVCP position: _____________ 

Fuel Gas Analysis: include representative fuel gas analysis 

Fuel Meter: make __________ model # __________ accuracy __________ ± %

Fuel Line: pressure _____________ (psig) temperature ____________ °F 

EPA Test Method deviations

Describe all deviations: 

________________________________________________________________________________ 

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________ 

Test Company ___________ email address ______________ Phone number __________ 

Contact 

Ambient Test Conditions

Temperature __________ Atmospheric Pressure __________ Relative Humidity _________ 

Optional Information 

Exhaust Temperature __________ 

Measured Fuel __________ 

Sample Port Location Description __________________________________________________ 

________________________________________________________________________________ 

________________________________________________________________________________ 
October 2, 2009 

Final Draft Test Plan 

12 

Attachment 2 

Selected FTIR Test Companies: Note that this list is for informational purposes only and does 

not represent an endorsement of any source test firm 

ACCT a Division of CECO

5440 Alder, Houston, TX 77081-1798

(800) 836-7333 

Fax (713) 664-6444 

actt@ceconet.com

Spectral Insights LLC

214 Argonne Drive

Durham, NC 27704

(919) 620-6549

www.spectralinsights.com

Air Compliance Testing, Inc.

5525 Canal Road 

Cleveland, Ohio 44125

216-525-0900

www.aircomp.com

TRC Environmental Corporation 

Ross A. Thompson

Lead Project Manager - Operations Manager - 

Lubbock Air Measurements

7902 Oakridge Avenue Suite One

Lubbock, Texas 79424

806/ 744-8422 Office

806/ 744-8423 Fax

806/ 773-8851 Cell

rthompson@trcsolutions.com

Air Hygiene, Inc.

Paul Little

Director of Customer Service

5634 South 122nd East Avenue, Suite F

Tulsa OK 74146

(918) 289-6378

www.airhygiene.com

Clean Air Engineering, Inc. 

500 W. Wood Street 

Palatine, IL 60067, USA 

800-627-0033

www.cleanair.com

Enthalpy Analytical, Inc.

Bryan Tyler 

2202 Ellis Road

Durham, NC 27703

919.850.4392 

bryan.tyler@enthalpy.com

Pace Analytical

1700 Elm Street SE 

Minneapolis, MN 55414

(612) 607-6398

www.pacelabs.com
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