# Technical Support for the Stack Testing Option for Estimating Fluorinated Greenhouse F - GHG Emissions from Electronics Manufacturing Facilities under Subpart I Office of Air and Radiation, U.S. Environmental Protection Agency August 2012August 2012 Subpart I Stack Testing Technical Support

Page 2 of 25 **1. Introduction**  This document presents technical information supporting the proposed stack test ing option for estimating fluorinated greenhouse gas (F - GHG) emissions from electronics manufacturing facilities required to be reported under subpart I, Electronics Manufacturing, of the Greenhouse Gas Reporting Program (GHGRP) . The EPA is proposing the stack test ing option as an alternative to using defau lt emission factor ( EF ) - based methods for estimating F - GHG emissions (see Technical Support for Modifications to the Fluorinated Greenhouse Gas Emission Estimation Method Option for Semiconductor Facilities under Subpart I) . The EPA propos ed stack test ing method would not apply to estimating N 2 O emissions (see Technical Support for Other Technical Issues Addressed in Revisions to Subpart I for more information on estimating N 2 O emissions) . This document was developed using information from materials submitted to the EPA by the Semiconductor Industry Association (SIA). Specific stack testing reports with results from test s performed by Intel Corporation , IBM, and Texas Instruments, which are referenced throughout this document, are available in the docket EP A– HQ –OAR–2011 -0028. 1 **2. General**  **Description of and Support for Inclusion of the Stack Test Option**  Under other EPA programs and some other subparts under the GHGRP, facilities have the option to estimate emissions using EF s developed by measuring emissions from their stacks over a certain period of time and dividing them by an activity metric (e.g., production) measured over the same period. This approach, hereinafter referred to as “stack testing” was not previously considered to be a viable option for measuring and estimating greenhouse gas emissions from t he electronics manufacturing sector, mainly because of technical issues found with quantifying low concentrations of F- GHG s in stack exhaust stream s ( Intel, 20 10 ) . However, new testing work conducted by SIA members using enhanced Fourier transform infrared spectroscopy ( FTIR ) techniques showed that gas and fab - specific EFs based on stack testing could be developed and used to estimate F - GHG emissions. Therefore the EPA is propos ing to include periodic stack testing as an option for electronics manufacturing fabs to estimate and report F GHG emissions under subpart I. This method is expected to provide a range of benefits, such as: i) a llow ing for estimation of emissions based on periodic, direct measurements of stack emissions from fabs ; ii) reduc ing industry concerns about exposure of confidential business information (intellectual property ) that would be reported to the EPA under other methods; and iii) possibly reducing compliance costs compared to the use of default EF - based method s for certain fabs having a limited number of stacks . The EPA is not proposing to address N 2 O emissions through a stack testing method, and is instead proposing that fabs continue to rely on default N 2 O EFs provided in subpart I . This is because a review of

1 Seethe following test reports: IBM 300mm Fab Stack Test Report and appendices, dated March 15, 2012; Test Report for the Enhanced FTIR Stack Sampling of Greenhouse Gases (GHG): Alternative Study for 40CFR98 Subpart I Reporting Requirements, dated September 2011 and appendices;, and FAB 32 GENERAL SCRUBBER END OF PIPE (EOP) GHG EMISSIONS ASSESSMENT STUDY , dated September 2011.August 2012 Subpart I Stack Testing Technical Support

Page 3 of 25 SIA stack test data provided to the EPA revealed inconsistent results for stack measurements of N 2 O emissions for which the cause could not be determined ( for N 2 O stack test data , refer to SIA, 2012g). Due to the inconsistent N 2 O test results, the EPA concluded that there was not sufficient data to show that stack testing is an appropriate and viable option for estimating N 2 O emissions. The remainder of this document discuss es the elements of the stack t est method , including:  Determining which stack systems to test;  Determining which F - GHGs to test for;  Developing EF s based on stack testing;  Estimating Fab F - GHG emissions;  Stack testing frequency; and  Changes at a fab t hat would t rigger re -testing of stack systems . **3. Determining the Stack Systems to Be Tested**  Many fabs have multiple stack system s 2 that emit F - GHGs. In order to provide accurate fab emission estimates while avoiding excessive burden from measuring emission s from multiple stack system s, the EPA is proposing that a fab would not be required to test certain “low emitting” stack systems for the purpose of develop ing gas and fab - specific EFs. (Emissions from low- emitting stack systems would be estimated using default EFs provided in subpart I , see Section 6 of this document .) The EPA is proposing to define a low- emitting stack system that is not tested as one that meets all of the following three criteria : 3 1. The sum of the F - GHG emissions from all combined stack systems in the fab that are not tested is less than 10,000 metric ton CO 2 e (mtCO 2 e) per year; 2. Each of the stack systems that are not tested are within the fab’s lowest F - GHG emitting stack systems that together emit 15 percent or less of total fab F - GHG CO 2 e emissions; and 3. The F - GHG emissions from each of the stack systems that are not tested can be attributed to only one particular collection of process tools during the test (i.e., the stack cannot be used as a bypass from other tools that are normally vented through a stack system that does not meet these criteria). Each of the elements of this definition and the supporting rationale are described in the following paragraphs. The EPA is proposing a 10,000 mtCO 2 e per year absolute threshold for the combined emissions from the low- emitting stack system s that are not tested at a fab . This threshold was selected so that testing would be focused on the largest emitting stack systems . The EPA is proposing that t he 10,000 mtCO 2 e threshold not be applied to individual stack systems be cause some fa b s have large numbers of stack

2 The EPA is proposing that a stack system would be defined as one or more stacks that are connected by a common header or manifold, through which a fluorinated GHG - containing g as stream originating from one or more fab processes is, or has the potential to be, released to the atmosphere. For purposes of subpart I , a stack system would not include emergency vents or bypass stacks through which emissions are not usually vented und er typical operating conditions. 3 The definition of a low - emitting stack system is modified from criteria suggested by the SIA. See SIA, 2012d.August 2012 Subpart I Stack Testing Technical Support

Page 4 of 25 systems with relatively low F - GHG emissions from each system . Therefore , setting a threshold on total fab emissions as opposed to individual stack system emissions ensures that a relatively large portion of the F - GHG emissions are estimated using EFs based on direct fab measurements. The EPA considered similar issues in establishing a threshold (10,000 mtCO 2 e) in subpart L, Production of Fluorinated Gases, for lower- emitting process vents. For such vents, subpart L allows facilities to calculate emissions based on EFs developed through a facility- specific engineering assessment instead of through direct meas urements. Please refer to the subpart L Technical Support Document (Technical Support Document for Emissions from Production of Fluorinated Gases: Final Rule for Mandatory Reporting of Greenhouse Gases, November 2010) available in docket EPA- HQ- OAR - 2009 -09 27, for more information on the similar issues considered in selecting the threshold adopted in subpart L . Because emissions from different fabs may vary widely depending on the processes used, the types of products manufactured, and the extent to which F - GHG abatement systems are installed , the EPA is proposing to also limit the total emissions from the low- emitting stack system s that are not tested to no more than 15 percent of total CO 2 e F - GHG emissions from the fab. This relative threshold ensures that a fab’s highest emitting stack systems are being tested while reducing the burden of testing stacks that account for a small share of total facility emissions. In addition, because F - GHG emissions from lowemitting stack systems may be more dilute than those from higher- emitting systems, the provision avoids technical concerns that may be associated with detecting and measuring these emissions. The third criteri on presented above , that the stack system cannot be used as a bypass for emission from other tools at the fab, is an essential part of defining low- emitting stack systems because it ensures that emissions that are measured during a stack test are representative of a consistent configuration of the fab’s exhaust system. Und er this definition, emissions from stack systems that are tested could not be diverted, during testing, to stacks that are exempt from testing. This provision ensures that together, the stack test and the default EF approach for low- emitting stack systems capture emissions from all of the F - GHG emitting tools in the fa b . Once testing was completed, exhaust systems could be reconfigured without reducing the accuracy of emission estimates as long as one of the following conditions was met : (1) tools and t heir emissions were tracked according to the configuration of the exhaust system at the time of the stack test (that is, the gas consumption of the tools that were associated with the tested stacks would be multiplied by the measured stack EFs even if thos e tools were later exhausted to the low- emitting stack system or vice versa), or (2) reconfigurations in exhaust systems were limited to a small percentage of the tools served by each system. Either of these conditions would ensure that the stack EFs rema ined representative of the emissions from the tools to which they were applied. In order to estimate emissions for purposes of determining whether a stack system is low- emitting, the EPA is proposing that fa bs use a method based on the 2006 Intergovernmental Panel on Climate Change ( IPCC ) Tier 2a method for the electronics manufacturing industry . 4 A Tier 2a method in electronics manufacturing relies on default gas - specific EFs ( i.e., kg gas emitted per kg of gas used ) and estimates of 4 For discussion about the Tier 2a method refer to the 2006 IPCC Guidelines and Technical Support Document for Process Emissions from Electronics Manufacture (e.g., Micro - electro-mechanical systems, liquid crystal displays, photovoltaics, and semiconductors): Proposed Rule for Mandatory Reporting of Greenhouse Gases, Revised – November 2010.August 2012 Subpart I Stack Testing Technical Support

Page 5 of 25 gas con sumption . The method also allow s the option to take into account the use of abatement systems. This approach minimiz es reporting burden to industry because it does not require allocation of gas consumption between process types or sub -types (e.g., etch and chamber clean ), as is required for other default - EF based methods in subpart I . In using the Tier 2a method t he EPA is proposing that electronics manufacture rs rely on 1) Tier 2a EFs specific to each type of electronics product manufactured, (see S ecti on 6 for more details) , 2 ) historical estimates of abatements system destruction or removal efficiency ( DRE ) , fab uptime , and gas consumption , 3 ) gas apportioning factors for stack systems that are based on the number of tools associated with each stack system (i.e., the fraction of an F - GHG apportioned to a stack system is equal to the fraction of all tools using that F - GHG that are vented to that stack system) , and 4 ) global warming potentials of gases used 5 as inputs to the equations to calculate emissions. See Section 6 of this memo for a discussion o f how the EPA is proposing that facilities would estimate emissions from low- emitting stack systems for reporting purposes. **4. Determini**  **ng Which**  **F -** **GHGs to Test**  **4.1. Input Gases**  In developing the proposed stack test ing method , there was a need for a mechanism to address F - GHG s that are used infrequently. This is because it may be difficult (and perhaps impossible) to schedule stack testing for a time when the fab is using every gas that it uses at some poin t during the reporting year. The EPA is therefore proposing that fabs have the option to exclude from stack measurements any F GHG that meets the definition of an intermittent low- use F - GHG as presented below . 6 The EPA is proposing to define a n intermittent low- use F - GHG as one that meets all of the following three criteria: 1. The F - GHG is used by the fab but was not used during the period of actual stack testing; 2. The emissions of that F - GHG do not constitute more than 5 percent of the total annua l F - GHG emissions from the fab on a CO 2 e basis; and 3. The sum of all F - GHG s that are considered intermittent low- use F - GHGs does not exceed 10,000 metric tons CO 2 e for that year. During stack tests, fabs would not be required to measure the F - GHGs that meet all three of these criteria .

5 Where no GWP is published in Table A- 1 of subpart A, the EPA is proposing that a global warming potential of 2,000 be used for the purposes of subpart I . The 2,000 value was selected based on an evaluation of all the known GWPs for fluorocarbon F– GHGs as listed in Table A– 1 to subpart A. The average for all of the fluorocarbons in this list was 2,300. The EPA believes that most perfluorocarbons (PFCs) whose vapor pressures qualify them as fluorinated GHGs already have their GWPs listed in Table A– 1. The average GWP of the fluorocarbons other than the PFCs is approximately 1,600. (Hydrofluorocarbons (HFCs) have an average GWP of about 2,000, while hydrofluoroethers (HFEs) have an average GWP of about 1,200 to 1,400 ). 6 This definition is modified from criteria suggested by the SIA. See SIA, 2012h.August 2012 Subpart I Stack Testing Technical Support

Page 6 of 25 Within criterion 3 above, the EPA is proposing a maximum allowance of 10,000 mtCO 2 per year for all intermittent low- use F - GHG combined. This is consistent with the proposed maximum allowance for low- emitting stacks (see S ecti on 3, above). T he EPA is proposing that fabs use the Tier 2a method as described Section 3 of this memorandum to estimate emissions for the purpose of determining whether an F - GHG is considered to be an intermittent low- use F - GHG by meeting criterion number 2, above . As part of defining intermittent low- use F - GHG s, the EPA set the relative threshold in criterion number 2 to ensure that the majority of F - GHG emissions are estimated based on actual fab measurements under the stack test method. The EPA evaluated various options for setting the relative threshold, including 15 percent, 10 percent, 5 percent, and 3 percent in combination with the 10,000 mtCO 2 e absolute threshold (criterion number 3, above) . To select the proposed threshold , the EPA estimated fab emissions using gas consumption data submitted by SIA (SIA, 2012a) , the IPCC Tier 2a EFs (IPCC, 2006) , and assum ing no abatement. Th e results of this analysis are presented in Table 1 below. **Table 1. Analysis of Intermittent -**  **Low Use F** **- GHG**  **Relative Thresholds (Source: SIA, 2012a ;**  **and IPCC, 2006)** 

In reviewing the results, it is apparent that a 15 percent threshold c ould result in testing of only two F GHG s in all but one of the analyzed facilities; in one case, the facility would test for thre e F - GHG s . Each **15% Threshold 10% Threshold**  **5% Threshold 3% Threshold**  **Fab, Year,**  **Wafer Size Number** 

**of Gases Used**  Number

of F - GHG Require d to Be Tested Percent of

Emissions from Low Use F GHGs Number

of F - GHG Required to Be Tested Percent of

Emissions from Low Use F GHGs Number of

F - GHG Required to Be Tested Percent of

Emissions from Low Use F GHGs Number of

F - GHG Required to Be Tested Percent of

Emissions from Low Use F GHGs Fab A, 2009, 300 mm 7 2 9% 2 9% 2 9% 4 1% Fab A, 2010, 300 mm 8 2 6% 2 6% 2 6% 2 6% Fab B, 2009, 200 mm 9 2 13% 2 13% 3 5% 3 5% Fab B, 2010, 200 mm 9 2 17% 2 17% 3 8% 4 5% Fab C, 2009, 200 mm 8 2 17% 2 17% 4 2% 4 2% Fab C, 2010, 200 mm 8 3 21% 4 9% 5 3% 5 3% Fab E, 2009, 300 mm 10 2 12% 2 12% 3 6% 3 6% Fab E, 2010, 300 mm 9 2 12% 2 12% 3 5% 4 2% Note: The analysis in Table 1 is theoretical. The percentage of emissions comprised of intermittent low - use F - GHGs is uncertain because fabs would be required to measure for all F - GHG that are being used as input gases during the test, and whether or not a particular input gas is used during the test depends on actual fab manufacturing. Therefore, the percentages in Table 1 repr esent the maximum percentage that could be comprised of F - GHG meeting the definition of intermittent low - use F - GHGs.August 2012 Subpart I Stack Testing Technical Support

Page 7 of 25 facility analyzed typically used a total of seven to 10 F- GHG s, as shown in Table 1. The 15 percent threshold would also result in a significant portion of the potential emissions ( six percent to 21 percent, based on SIA- provided F - GHG consumption distributions) be ing represented by F - GHG potentially meeting the definition of intermittent low- use F - GHG and not subject to mandatory test ing during the fab - specific stack measurements. Reducing the threshold from 15 percent to 10 percent wo uld not significantly increase the number of F - GHG s that would be tested or reduce the percentage of potential emissions from intermittent low- use F - GHG s. Changing to a five percent threshold for individual F - GHG s would reduce the potential percentage of total emissions from intermittent low- use F - GHG s to less than 10 percent for all fabs covered in Table 1 , while only moderately increasing the burden associated with the minimum number of F -GHG s to be measured . Decreasing the threshold from 1 0 percent to five percent would increase the minimum number of F - GHG s to be tested from two F- GHG to three F - GHG at five of the facilities analyzed . Using a three percent threshold for individual F - GHG s would drop the percentage of potential emissions from intermittent low use F - GHG s to no more than six percent while increasing the minimum number of F - GHG s to be tested from two to four F - GHG s at one facility, and from three to four F - GHG s at two facilities . However, under a three percent threshold, a fa b would be required to measure gases that may be used only rarely, presenting significant scheduling hurdles. The proposed relative threshold of less than five percent of the total estimated emissions for the definition of intermittent low - use F - GHGs w ould result in actual testing of greater than 90 percent of overall emissions from tested stack systems . In terms of the minimum number of F - GHG s tested, this w ould represent (on average) about one -third of the total number of F - GHG s used, but would increase technical feasibility compared to testing all F - GHGs . As noted above, t he actual number of F - GHG s tested would depend on which F - GHG s are actually being used when the stack testing is conducted. If a F - GHG does not meet the proposed definition of an inter mittent low- use F - GHG , and was not used during the emissions test, an additional stack test would need to be conducted in the reporting year during a period when that gas is being used . However, i f a F - GHG that was not an intermittent low- use F - GHG is no l onger used, re -testing would not be required, and F - GHG emissions would be calculated according to the process for intermittent low use F - GHG s . See S ection 6 for a discussion on how the EPA is proposing to estimate emissions of the intermittent low- use F - G HGs for reporting purposes. **4.2. By** **- Products**  In addition to identifying input gases to test for in stack systems it is important to identify known byproducts of process es used at the fab that will also have to be tested for. By- product emissions are estimated to make up from 14 to 19 percent of emissions at 200 mm fab s and from 14 to 24 percent of emissions at 300 mm fab s . 7 Table 2 below shows a survey of known by- product s from electronics manufacturing .

7 The EPA analyzed two gas distributions for 200mm and 300 mm fabs provided by SIA along with the revised default emission factors in subpart I to determine this percentage (see SIA, 2012a and Tables I - 3 an d I -4 of the proposed subpart I). The lower and upper bounds were based on by- product formation factors that included and excluded zeros, respectively. (For more discussion of the treatment of zeros, see the proposed rule and “Technical Support for Modifications to the FluorinatedAugust 2012 Subpart I Stack Testing Technical Support

Page 8 of 25 **Table 2. Common Electronics Manufacturing By -**  **Product Gases Source**  **Identified By -**  **Products** 2006 IPCC Guidelines for National Greenhouse Gas, Volume 3, Chapter 6 CF 4, C 2 F 6, C 3 F 8, CHF 3 International SEMATECH Manufacturing Initiative Environmental Safety and Health Technology Center Etch Process Equipment Emissions Characterization Data (SIA, 2012b) CF 4, C 2 F 6, C4 F 8, C4 F 6, CHF 3 Response to EPA’s Stack Test Question 1 (SIA, 2012g) CF 4, C 2 F 6, C 3 F 8 In reviewing Table 2 , it can be seen that CF 4 and C 2 F 6 are common by- products identified across all sources surveyed. Therefore , the EPA is proposing that all fabs using the stack testing method specifically test for CF 4 and C 2 F 6, even in situations when they are not used as input gases (i.e., are emitted only as by- products). In addition to proposing that these testing always include CF 4 and C 2 F 6, the EPA is also proposing that fabs analyze and document any expected by- products (other than CF 4 and C 2 F 6 ) for the upcoming repo rting year. The EPA is proposing that any identified by- products be tested for as well during the reporting year . Expected by- products would be identified by an analysis of any possible F - GHG by- products formed from the input gases (F - GHGs) used in the previous reporting year and expected to be consumed in the current reporting year. When developing this analysis the EPA is also proposing that fabs consider at a minimum the by- products identified in Tables I - 3 through I - 7 of subpart I (or those identifie d in the second row of Table 2, found in SIA, 2012b). Another option that the EPA is considering is to require testing for all F - GHGs that have been identified as by- products of any input gas in previous testing throughout the electronics industry. This s et would include C 3 F 8, C4 F 6, C4 F 8, and CHF 3 in addition to CF 4 and C 2 F 6 . The EPA is considering this option because the identities and quantities of by- products generated at a particular fa cility at a particular time can be difficult to predict, and the costs of testing for additional by- products are expected to be modest. In the one set of semiconductor faci l ity stack tests that tested for the full range of potential by- products listed above, a F - GHG by- product was found for which there are no by- product formation factors listed in Tables I - 3 and I -4 (the default EFs tables applicable to semiconductor facilities). This was C 3 F 8, which accounted for 40% of the GWP -weighted by- product emissions of the fab (2% of the total GWP weighted emissions) in one of the two tests at the fab. (In the other test, the C 3 F 8 emissions accounted for a much smaller, but still measurable, share of emissions.) If unexpected by- products occur in similar proportions a t other facilities, failing to measure for them could lead to routine underestimates of emissions at those facilities. Once a method has been validated for all potential by- product gases, the costs of testing for six, as opposed to two, of these gases are expected to be low. All gases would be tested for at the same time by the same equipment and personnel. The only additional costs would be those associated with the analysis of the resulting data, which is performed automatically. It appears very unli kely that these Greenhouse Gas Emission Estimation Method Option for Semiconductor Facilities under Subpart I,” Docket ID. No EPA- HQ- OAR 2011 - 0028 . )August 2012 Subpart I Stack Testing Technical Support

Page 9 of 25 additional costs would exceed 10% of the overall costs of stack testing, and they would probably be considerably less. **5. Developing**  **Gas -** **Specific and Fab** **- Specific**  **E mission**  **F actors**  The proposed subpart I stack test ing option would require fa bs to develop EFs based on a correlation between measured gas consumption and stack emission s for all stack systems tested and for all F - GHGs tested . The EFs for input F -GHG s would be in the units of kilograms of the F - GHG emitted per kilogram of the F - GHG consumed. The EFs for a by- product F - GHG that is not used as an input F - GHG would be in units of kilograms of the by- product F - GHG emitted per kilogram of all F - GHG consumed as input gases combined. If an input F - GHG’s emissions exceeded its consumption, then the emissions in excess of consumption would be treated as if they were by- product F - GHG emissions, except that the denominator in the EF would not include the consumption of that F - GHG (See Section 5.3) . **5.1. Measuring Stack**  **F**

**- GHG Emissions**  This section address es the provisions related to stack measurements of F - GHGs, including measurement methods, durations of testing, field detection limits, and treatment of emission concentration s below the field detect ion limit s. The proposed stack testing option woul d require fa bs to measure F - GHG emissions for all F - GHG used as inputs to processes and for any expected by- product F- GHG s, except for F - GHG emitted from lowemitting stack systems and for F - GHG that meet the definition of intermittent low- use gases . **5.1.1. Measurement Methods**  The calculation of fab EFs are based on (1) the measurements of the concentrations of F - GHGs in the stack system s and (2) on the measurement of the stack flows. The EPA is proposing that EPA Method 320 be used to measure the concentration of F - GHGs in the stack system s using FTIR . Ple ase refer to Method 320 for detailed information about the measurement method and procedures. 8 Please note that in utilizing the work performed by SIA member companies (Intel, IBM, and Texas Instruments) in consultation with the EPA, the use of this method for stack testing to measure F - GHG emissions at electronics manufacturing facilities has been validated using Section 13 of Meth od 320 . SIA member companies provided EPA with timely stack testing plans and reports at the beginning of the process that were invaluable to evaluating Method 320 at these facilities. For the measurement of the stack gas volumetric flow rate s, the EPA is proposing to use Methods 1 9 or 1A 10, and Methods 2 11, 2 A 12, 2C 13, 2D 14, 2F 15 or 2G 16 . These methods are based on the measurement of

8 Measurement of Vapor Phase Organic and Inorganic Emissions by Extractive Fourier Transform Infrared Spectroscopy . Method 320 can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 320.pdf 9 Sample and Velocity Traverses for Stationary Sources. Method 1 can be accessed at http://www.epa .gov/ttn/emc/promgate/m - 01.pdf 10 Sample and Velocity Traverses for Stationary Sources With Small Stacks or Ducts . Method 1A can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 01a.pdf 11 Determination of Stack Gas Velocity and Volumetric Flow Rate (Type S Pitot Tube). Method 2 can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 02.pdf 12 Direct Measurement of Gas Volume Through Pipes and Small Ducts. Method 2A can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 02a.pdf 13 Determination of Gas Velocity and Volumetric Flow Rate in Small Stacks or Ducts (Standard Pitot Tube). Method 2C can beAugust 2012 Subpart I Stack Testing Technical Support

Page 10 of 25 the gas velocity and also require the measurement of the gas molecular weight using Methods 3 17, 3A 18, or 3B 19, and measurement of the stack’s moisture content using FTIR or Method 4 . 20 Please refer to Table I - 9 in subpart I for more information and to the links in the footnotes within this paragraph for more details on the proposed methods for determination of the stacks’ flow rate s. For supporting data and information on the proposed use of the methods described above in stack testing, please refer to Intel Corporation, IBM, and Texas Instruments test reports available in the EPA docket EPA– HQ

–OAR–2011 - 0028. Throu gh testing, it has been shown that the identified methods are viable options for measuring F - GHG emissions from semiconductor ( and other electronics ) manufacturing. The EPA is also proposing to allow fabs to use alternative measurement methods for stack system testing to provide flexibility in the rule . This is consistent with the flexib i l ity provisions provided to reporters in other subparts, such as subpart L (see Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs, published December 2010, ( 75 FR 74774) ) . An alternative method is any method of sampling and analyz ing for a n F - GHG that is not a method specified in s ubpart I. The EPA is propos ing that a lternative test methods would have to be validated according to EPA Method 301 ( Field Validation of Pollutant Measurement Methods From Various Waste Media ). 21 Prior to using an alternate test method , the facility would be required to submit the method along with a proposed test plan to the EPA for review and approv al by the EPA . This process would ensure that any method outside of those specified in subpart I is viable and appropriate. Once the EPA approves an alternate method , the method could be used by other fab s that meet the same conditions under which the alternative method was approved. The EPA would specify those conditions in the approval of the alternati ve method. **5.1.2. Maximum**  **Field Detection Limits** In using Method 320, maximum field detection limits (FDLs) need to be specified because the FDLs achieved by a method and analytical instruments can have a significant impact on the quality of the measurements. 22 Th e maximum FDLs are the limits at which an F - GHG should be detectable when the accessed at http://www.epa.gov/ttn/emc/promgate/m - 02c.pdf 14 Measurement of Gas Volume Flow Rates in Small Pipes and Ducts . Method 2D can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 02d.pdf 15 Determination of Stack Gas Velocity And Volumetric Flow Rate With Three - Dimensional Probes. Method 2F can be accessed at http://www.epa.gov/ttn/emc/promgate/Methd2F.pdf 16 Determination of Stack Gas Velocity and Volumetric Flow Rate With Two - Dimensional Probes. Method 2G can be accessed at http://www.epa.gov/ttn/emc/promgate/Methd2G.pdf 17 Gas Analysis for the Determination of Dry Molecular Weight . Method 3 can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 03.pdf 18 Determination of Oxygen and Carbon Dioxide Concentrations in Emissions From Stationary Sources (Instrumental Analyzer Procedure). Method 3A can be accessed at http://www.epa.gov/ttn/emc/promga te/method3A.pdf 19 Gas Analysis for the Determination of Emission Rate Correction Factor or Excess Air. Method 3B can be accessed at http://www.epa.gov/ttn/emc/promgate/m - 03b.pdf 20 Determination of moisture content in stack gases . Method 4 can be accessed at http://www.epa.gov/ttn/emc/promgate/m 04.pdf 21 Method 301 can be access at: http://www.epa.gov/ttn/emc/methods/method301.html 22 Method 320 defines a required detection limit = for the i th analyte, the lowest concentration of the analyte for which its overall fractional uncertainty (OFUi) is required to be less than the an alytical uncertainty limit (AUi).August 2012 Subpart I Stack Testing Technical Support

Page 11 of 25 method is conducted properly and the analytical instruments are used correctly and of reasonable quality . If the FDL for an F -GHG were so high that it represented a relatively large fraction of th e fab’s emissions of that F - GHG, the uncertainty of the resulting emission estimate would be correspondingly high. Therefore, the EPA is proposing maximum FDLs for stack tests for electronics manufacturing facilities. Fabs using the sta ck testing option would need to achieve FDLs at or below the maximum FDLs in order for the stack testing results to be acceptable for estimating F - GHG emissions. The FDL would be determined for each stack test for each analyte by the person conducting the stack test. The proposed maximum FDLs, in parts per billion by volume are presented in Table 3 below.

**Table 3**  **. Proposed Maximum Field Detection Limits (Table I -**  **10 in Subpart I) Analyte**  CF 4 C 2 F 6 C 3 F 8 C4 F 6 C 5 F 8 C4 F 8 CH 2 F 2 CH 3 F CHF 3 NF 3 SF 6 Other fully fluorinated GHGs Other

fluorinated GHGs **Maximum FDLs (ppbv)**  5 5 5 5 5 5 10 10 5 5 1 5 10 T he proposed maximum FDLs are based on (1) the EPA’s review of the FDLs that have been achieved at three different semiconductor facilities ( please refer to Intel Corporation, IBM, and Texas Instruments test reports available in docket EPA – HQ –OAR–2011 -0028 ) , and (2) an analysis of the magnitude of the emissions that would occur (in CO 2 e) at various possible maximum FDLs. (The latter provides an indication of the uncertainty of emission measurements using methods and analytical instruments with those FDLs.) The results of this review and analysis are presented in Table 4, below. Table 4 presents the EPA’s analysis of how the proposed maximum FDLs translate into corresponding F GHG emissions at the proposed maximum FDLs . To determine th ese emissions, the EPA used the known molecular weights for each gas, an assumed fab -wide stack flow rate, and simple unit conversions.August 2012 Subpart I Stack Testing Technical Support

Page 12 of 25 **Table 4**  **. Emissions at**  **Proposed Maximum**  **Field Detection Limits**  **Analyte Maximum** 

**FDL (pp**  **b v)**  **M olecular** 

**W eight**  **(g/mole) Assumed Fab**  ****

**Wide Flow rate (scfm)**  **kg/min kg/yr**  **mt/yr GWP**  **mtCO2e/yr** CF 4 5 88 150,000 7.77E -05 41 0.04 6500 266 C 2 F 6 5 138 150,000 0.000122 64 0.06 9200 590 C 3 F 8 5 188 150,000 0.000166 87 0.09 7000 611 C4 F 8 5 200 150,000 0.000177 93 0.09 8700 808 CH 2 F 2 1 0 52 150,000 9.19E -05 48 0.05 675 33 CHF 3 5 70 150,000 6.18E -05 33 0.03 11700 380 NF 3 5 71 150,000 6.27E -05 33 0.03 17200 567 SF 6 1 146 150,000 2.58E -05 14 0.01 23900 324 **Total 3,578**  In reviewing how the proposed FDLs for specific gases translate into emissions it can be seen that t he proposed maximum FDLs are lower for F - GHGs that have higher GWPs and are easier to detect (e.g., SF 6, for which a maximum FDL of 1 ppbv is proposed) and higher for F - GHGs that have lower GWPs and are more difficult to detect (e.g., CH 3 F, for which a maximum FDL of 10 ppbv is proposed). For perfluorocarbons and CHF 3, the EPA is proposing maximum FDLs of 5 ppbv. The proposed maximum FDLs are generally, though not always, close to the average FDLs achieved across all three facilities that submitted FDL information to the EPA (see IBM, Intel, and Texas Instruments test reports in docket EPA– HQ –OAR–2011 - 0028 ) . All of the maximum FDLs are higher than the FDLs achieved at the two facilities that used enhanced FTIR during their stack testing. Emissions of F - GHGs at the maximum FDLs generally range between 200 and 800 mtCO 2 e per gas, based on a total flow rate at the fab of 150,000 standard cubic feet per minute ( s cfm), totaling approximately 3,600 mtCO 2 e for commonly used F - GHGs with GWPs in Table A- 1. Thus, the maximum FDLs are readily achievable using proven detection technology but are low enough to ensure qual ity data are used to develop stack EFs . (It is important to note that at an actual facility comparable to the example represented by Table 4, the most commonly used F - GHG s would be measured in concentrations that are well above the proposed maximum FDL, a nd the total emissions of the F - GHG that are at or below the proposed maximum FDL would be substantially lower .) As seen in Table 3 , the EPA is also proposing maximum FDLs for two broad categories of F - GHGs, “ Other fully fluorinated GHGs 23” and “ Other fluo rinated GHGs”. The EPA is including these categories because not all known F - GHGs used in electronics manufacturing (e.g., C4 F 8 O) were tested as part of the stack

23 Fully fluorinated GHGs is being proposed as fluorinated GHGs that contain only single bonds and in which all available valence locations are filled by fluorine atoms. This includes but is not limited to saturated perfluorocarbons, SF6, NF3, SF5CF3, C4F 8O, fully fluorinated linear, branched and cycl ic alkanes, fully fluorinated ethers, fully fluorinated tertiary amines, fully fluorinated aminoethers, and perfluoropolyethers.August 2012 Subpart I Stack Testing Technical Support

Page 13 of 25 testing used to develop this proposed stack method still other F - GHGs may be used or emitted in the future. The maximum FDL proposed for “fully fluorinated GHGs” is 5 ppbv, the same as that proposed for all the PFCs that have been tested to date. Like PFCs, other fully-fluorinated GHGs are relatively pot ent GHGs and are likely to be detectable in small quantities using FTIR. The maximum FDL proposed for “other fluorinated GHGs” is 10 ppbv, the same as that proposed for CH 2 F 2 (HFC- 32). Like HFC- 32, other fluorinated GHGs are likely to be less potent tha n fully fluorinated GHGs and somewhat more difficult to detect. **5.1.3. Test Durations**  **and Conditions** The EPA is proposing that stack test s be performed for a minimum of 8 continuous hours. For four different fabs the difference between the upper and lower conc entrations over an 8 hour difference at the 95 - percent confidence interval was typically less than 15 percent (SIA, 2011) . Also, the difference in day-to - day flow rates over 4 to 5 days was shown to be typically around one percent . Finally, a continuous measurement of CF 4 emissions during a 24 h ou r period showed that the mean concentration was 167 ppbv, while the lower and upper concentrations were 162 and 172 ppbv respectively (95 - percent confidence interval). Over the same 24 h ou r period, the 8 - h ou r run ning average ranged between 144 and 186 ppbv, yielding similar results to a 24 - h ou r sample time. Based on these results (from SIA, 2011 ) , the EPA determined tha t the proposed 8 - h ou r test duration would appropriately capture short term variations in stack e missions . The EPA is also proposing that facilities adhere to two conditions while conducting stack testing in order to ensure that EFs developed from stack tests are representative of fab emissions . First, w hile the EPA does not require that emissions from all stack systems be tested simultaneously, the EPA is proposing that there be no changes between tests in the stack flow configuration (i.e., the configuration of the ducts between sets of process tools and any connected point - of- use ( POU ) abatement systems and their corresponding waste streams that are ultimately vented through the stack) during the entire testing period. The EPA is also proposing that there be no changes in the centralized abatement systems during testing; if any are present (the EPA’s current understanding is that centralized abatement systems are rarely used in electronics manufacturing, if at all). This would ensure that emission s from each tool are measured by one and only one test (i.e., no emissions are missed or double counted). Second, the EPA is proposing that stack tests be conducted for a period during which the fab is operating at a representative operating level , 24 and with the POU abatement systems connected to the stack being tested operating with at least 90 percent uptime during the 8 - hour (or longer) period or at no less than 90 percent of the average uptime measured during the previous reporting year. This requirement would ensure that the EFs developed from stack tests are representative of fab operati ons over the reporting year.

24 The representative operating level is be ing proposed as operating the fab, in terms of substrate starts for the period of testing, at no less than 50 percent of installed production capacity or no less than 70 percent of the average production rate for the reporting year, where production rate for the reporting year is represented in average monthly substrate starts.August 2012 Subpart I Stack Testing Technical Support

Page 14 of 25 **5.1.4. Treatment of**  **F**

**- GHG Concentrations That are Below the FDL**  In performing stack measurements, fabs may have cases in which certain input F - GHGs ( excluding those that are classified as intermittent low- use gases) or emitted as by- product F - GHG s cannot be detected or are not continuously detected. For these situations, the EPA is proposing that:  If a n F - GHG is consumed during testing, but emissions are not detected, the reporter would use one - half of the FDL for the concentration of that F - GHG in calculations.  If a n F - GHG is consumed during testing and detected intermittently during the test run, the reporter would use the detected concentration for the value of that F - GHG when available and use one - half of the FDL for the value w hen the F - GHG is not detected.  If a n F - GHG is not consumed during testing but is detected intermittently as a by- product gas, the reporter would use the measured concentration when available and use one - half of the FDL for the value when the F - GHG is not d etected.  If a n F - GHG is a n expected by- product gas (e.g., CF 4, C 2 F 6 ) of the stack system tested and is not detected during the test run, the reporter would use one - half of the FDL for the value of that F GHG.  If a n F - GHG is not used, is not a n expected by- product of the stack system , and is not detected, then the reporter would assume zero emissions for that F - GHG for the tested stack system. The EPA is proposing to use half the FDL (note: this is the FDL as defined in EPA Method 320 and determined for each stack test, not the proposed maximum FDL), for these cases because t he EPA expects that the proposed treatment of these non - detect values will avoid any potential under- counting of any F - GHG that are expected to be in the emissions from a given process and F -GHG input gas combination. At the same time, the proposed treatment will provide a reasonable estimate of emissions of F - GHG that occur in concentrations that are below the FDL. The EPA’s analysis of testing data provided by SIA has shown that emission measurements of gases known to be used and for which the concentration was below the FDL accounted for about 0.1 percent of F - GHG consumption and would account for about 0.1 percent of emissions on a CO 2 e basis if the concentration was assumed to be one half of the FDL as outlined above . The measurements were at done at Texas Instruments and Intel fabs . At Texas Instruments, emissions of c - C4 F 8 (an input gas) were below detection; at one - half the FDL, emissions would be 65 mtCO 2 e per yea r and would represent 0.1 percent of total estimated facility emissions. At Intel, emissions of C H 2 F 2 (also an input gas) were below detection; at one - half the FDL, emissions would be 132 mtCO 2 e per yea r and would also represent 0.1 percent of total estima ted facility emissions. **5.2. Measuring Fab Activity (**  **F -** **GHG Consumption)**  The EPA is proposing that gas consumption be used as the metric of fab activity to develop fab - specific EFs from stack testing . Other potential metrics of fab activity, such as wafer movements, were considered ; however, a strong correlation between gas consumption and emissions ha s been shown over time (SIA, 2011 and SIA, 2012c ).August 2012 Subpart I Stack Testing Technical Support

Page 15 of 25 Data supplied by SIA for multiple fabs have shown that gas consumption is consistently linear over time and that emissions are also a linear function of gas consumption ( SIA, 2011 and SIA, 201 2c ). SIA provided the EPA with F - GHG consumption from four fabs for several different F - GHG s . For CF 4 and CHF 3, consumption data were available from three fabs, and for SF 6 and NF 3, data were available from four fabs. For all four of these F -GHG s, consumption data were available for time periods measured in hours, days, and months. These data showed that consumption of these four F - GHG w as linear over all of the time perio ds measured, including 8 - hour stack testing periods, periods of several days to weeks, and, at one fab, annual 12 - month calendar periods. Consumption data over a period of several hours were also available for C 2 F 6 from one fab, and consumption data over a period of a few weeks were available for C4 F 6, C4 F 8, and CH 2 F 2 from another fab. These data also showed that consumption was linear for these gases at these two fabs over the time periods measured. (SIA, 2012c). Based on these results, the EPA concluded that gas consumption was a good measure of fab activity, and that stack EF s could be expressed as a function of F - GHG consumption . Furthermore, the EPA concluded that these EFs based on monitoring emissions and F - GHG consumption for short time p eriods would be representative of longer term emissions such that they could be applied annually . However, there were some cases in the SIA data where the short -term correlation between consumption and emissions for CF 4, SF 6, and NF 3 could not be replicat ed for other F - GHGs during testing at fabs with limited consumption of the other F - GHG because the scales used in production for such gases could not resolve the ir weight change across the 8 - h ou r test period (SIA, 2012c) . Thus, for gases for which it may be difficult to accurately measure short -term (i.e. 8 - hour) consumption , the EPA is proposing that reporters would use one or more of the following measures to increase the accuracy of their consumption estimates, if needed : 1) Draw from sing le gas containers (instead of from multiple containers attached to a common manifold). 2) Calculate consumption from prorated long-term (e.g., monthly) consumption data. 3) Increase the length of the test period above 8 hours . T he EPA is proposing various options for measuring gas consumption during the test period : 1) Fabs could use measurement equipment (e. g . , gas flow meters, weigh scales, or pressure gauges) to monitor F - GHG consumption . 2) Gas consumption calculated based on pressure measurements would be corrected for temperature and non - ideal gas behavior according to the following : a) If a reporter measured gas consumption using pressure the reporter would either measure the temperature of the F - GHG contai ner when the sampling periods begin, end, and when containers are changed out, or measure the temperature every hour. b) Reporters would convert the measured pressures to masses using an appropriate equation of state and the measured temperatures. It is crit ical that gas consumption measurements based on changes in cylinder pressure be corrected for non - ideal gas behavior because measurements of gas consumption may sometimes be affected by temperature fluctuations that change gas pressure , especially with gas cylinders with low drawdownAugust 2012 Subpart I Stack Testing Technical Support

Page 16 of 25 rates . These issues may have a significant impact on the short -term gas consumption measurements used to establ ish EFs (SIA, 2012e ). **5.3. Estimating Abatement System**  **Downtime** For fabs that have F - GHG abatement systems associated wit h stack systems that are tested , it is critical to consider appropriately the downtime of those abatement systems for two purposes: 1) when developing stack EFs, and 2) when estimating emissions using stack-testing based EFs. For example, if the uptime of abatement systems is 100 percent during the period of time in which stack emissions are measured for developing an EF, yet average uptime for the fab for the reporting year is 85 percent, using an EF b ased on conditions where uptime is 100 percent would underestimate F - GHG emissions because it would not account for excess emissions during the time that the abatement system is no t operating . Therefore , the EPA is proposing methods for estimating the down time of abatement systems at a fab that uses stack testing and accounting for the excess emissions . To determine downtime for the purpose of developing stack EFs, t he EPA is proposing that the amount of abatement system downtime be estimated using the num ber of t ools, the total duration of the stack test ing period , and the duration of the abatement system downtime during the testing . 25 For example, if five POU abatement systems are down for times of 10, 15, 25, 30, and 40 minutes during an 8 - hour test, the total POU system downtime would be 120 minutes, or 5.0 percent of the total possible abatement system and tool operating time for th e five tools (2,400 minutes). Using these data and the average DRE for the POU abatement systems, the EF measured during the testing would be adjusted to an EF representing POU abatement systems with 100 percent uptime (zero percent downtime). The EPA is proposing that t he downtime measured over the year would be used to determine an uptime factor that would be an aggregate for all abatement systems in the fab, and that would be calculated using proposed Equation I - 23 in subpart I. This value would be used for calculating annual fab emissions . Abatement system downtime would be considered any time during which the abatement system was not installed, operat ed or maintained according to the manufacturer’s specifications. The fab’s operator would determine the sum of the downtime for all abatement systems during the year, and divide this sum by the sum of the possible annual operati ng time for each of the tools connected to those abatement systems in the fab to determine the downtime fraction. The downtime fraction would be the decimal fraction of operating time that the abatement systems were not installed, operat ed, and maintained according to the manufacturer’s specifications. The uptime fraction used in the emissions calculations would be equal to 1 minus th e downtime fraction. The total possible annual tool operating time would be calculated by assuming that tools that were installed for the whole of the year were operated for the entire year. The total possible tool operating time would be prorated to acco unt for the days in which a tool was not installed; any partial day that a tool was installed would be treated as a full day of tool operation . For an abatement system with more than one connected tool, the tool operating time would be equivalent to a full year if at least one tool was installed at all times throughout the year. The fab would also be able to account for time that tools are idle and no gas is flowing through the tools to the abatement system.

25 This meth od is based on a proposal from SIA. See SIA, 2012e.August 2012 Subpart I Stack Testing Technical Support

Page 17 of 25 The method outlined above is different than the m ethod for estimating uptime of abatement systems for the default EF based method , which requires an uptime to be determined for each gas and process type combination as opposed to calculating downtime and uptime based on an aggregate for all tools in the fab . This is because the default EF method requires emissions to be estimated based on process types (etch and CVD chamber cleaning), whereas the stack testing method looks at emissions by stack systems as opposed to by process type. Allowing the proposed simplified approach for calculating downtime for stack testing would reduce the burden on fabs that elect to do stack testing because it does not require tracking downtime for each gas and process type. To ensure that the simplifying assumption (i.e., the operation of abatement systems is consistent across gases, tools, and processes ) would not drastically impact emission estimates, the EPA performed an analysis to compare fab emissions if downtime is assigned to each type of tool (etch or chemical vapor de position) and fab emissions if downtime is assumed to be evenly distributed among all tools. The difference in emissions as calculated both ways in this analysis varied depending on the fraction of tools abated and the downtime assumed , increasing with bot h. Where the fraction of tools abated was assumed to be 100 percent and the average downtime was assumed to be 35 percent (both likely to be maximum values), the difference was about 5 percent of total (abated) emissions and about 3 percent of total unaba ted emissions. ( The error as a fraction of unabated emissions was calculated to permit objective comparisons between the errors at highly abated facilities with low absolute emissions and less abated facilities with high absolute emissions.) Further, th e simplifying assumption is not expected to have a substantive impact on overall facility emission estimates because abatement system uptime is generally high as seen by a sampling of fabs that submitted uptime data to the EPA; for example around or above 90 percent (SIA, 2012f). **5.4. Calculating Emission Factors**  The EPA is proposing that an EF be calculated for each F - GHG based on the aggregated results from all the tested stack systems at a fab . (These EFs would not be calculated for F - GHG s that are intermittent low- use F - GHG s . ) The E F s would be based on stack emissions measurements (kg F - GHG emitted) and gas consumption (kg of F - GHG consumed) for all higher emitting stack systems during the period of testing (e.g., 8 hours) using the calculation meth ods described in the proposed regulatory text . The result is an EF for input gases in the units of kg of F - GHG emitted per kg of F - GHG consumed , tak ing into account abatement system use and performance . For by- product F - GHG emissions that are not also used as input F - GHG , the EPA is proposing that the fab - specific by- product EF be calculated as the mass of the by- product F - GHG emitted divided by the summed masses of all the F - GHGs consumed; the calculation methods for which are also p resented in the propos ed regulatory text . The EF that is determined from the stack testing results would be corrected to account for any abatement system downtime that occurs during the actual stack testing. As described in S ection 5. 3 of this memo, the fab would correct the measured emissions to account for the abatement system downtime, and would use either default or measured DREs for the abatement system to calculat e gas and fab - specific EFs that reflect 100 percent uptime of all relevant abatement systems . Annual u nabated emissions used in accounting for abatement system downtime would be calculated as the measured EF divided by (1 – DRE).August 2012 Subpart I Stack Testing Technical Support

Page 18 of 25 **5.4.1. Treatment of F** 

**- GHGs For Which Emissions Exceed Consumption**  In some cases, emissions of a particular F - GHG input gas may exceed consumption of that gas because the F - GHG is generated as a by- product of the other input gases. This is often the case for CF 4 . In these cases, the EPA is proposing that the reporter equate emissions of the input gas to the consumption of that gas for purposes of calculating the F - GHG input EF 26 using Equation I - 19. This would result in a calculated input EF of 1.0. The reporter would treat the remainder of th e input gas’s emissions as a byproduct of the other input gases using Equation I - 20. In this instance, the denominator in Equation I - 20 would include the consumption of all the F - GHGs other than the F - GHG with the “extra” emissions . This treatment of the denominator reflects the fact that the EPA is assuming that the F - GHG in the n umerator is formed as a by- product from all other F -GHGs, while the emissions from the actual consumption of that F - GHG as an input are being accounted by proposed Equation I - 19. For example, if the fab consumed 100 kg of an F - GHG during the testing, but t he stack testing measured 300 kg of that gas, the reporter would treat 100 kg of that F - GHG ’s emissions as an input gas in proposed Equation I - 19, and 200 kg of that F - GHG’s emissions as a by- product gas in proposed Equation I - 20. For calculating emission s from an F - GHG with “extra” emissions, the input portion of emissions would be assumed to equal consumption of that F - GHG, and the by- product portion of emissions would be determined by multiplying the by- product EF by the sum of the consumption of all F - GHGs other than the by- product F - GHG. The advantage of this approach is that it reflects the physical mechanism through which emissions of an input gas exceed consumption of that gas. Because mass is conserved, the emissions of an input gas that are in e xcess of consumption of that gas must be attributable to the other input gases. These “extra” emissions are expected to vary with the facility’s consumption of the other input gases rather than with the facility’s consumption of the emitted gas with the “ extra” emissions. Reflecting this in the by- product EF would lead to more accu rate emission estimates and would help to prevent large swings in EFs that could result when consumption of the gas with the “extra” emissions varies from test to test. For ex ample, this could help a facility to avoid a 20 percent or greater relative standard deviation in its CF 4 EF, which would otherwise prevent the facility from qualifying to skip testing for five years (discussed further below). Note that the proposed approach includes a simplification that would in some cases affect the “extra” emissions that are reassigned as by- products of other input gases. Specifically, Equation I - 19 accounts for the application of abatement devices in developing the EF for each inpu t gas. This means that if abatement is used at a facility, an EF of 1.0 for a gas with extra emissions at that facility actually equates to a pre - abated EF of greater than 1.0 for that gas. In other words, some “extra” emissions continue to be included i n the input EF for that gas.

26 Here the terms “input emission factor” and “input portion of emissions” represent the emission factor and emissions reflecting the share of the consumption of the input F - GHG that survives utilization, i.e., 1 minus the utilization rate .August 2012 Subpart I Stack Testing Technical Support

Page 19 of 25 The impact of this simplification on the by- product emissions calculated under Equation I - 20 depends on the extent to which a particular input gas is also generated as a byproduct and especially on the overall level of abatem ent for the stack system tested, i.e., the fraction of tools with abatement systems and the DREs of those systems. Table 5 shows the differences in the fractions of emissions counted as byproducts with and without the simplification, based on a range of by- product generation rates and abatement levels. (For simplicity, the consumption during the test of the F - GHG with the extra emissions is equated to 1 kg, although this is lower than consumption of most gases is likely to be.)

**Table 5 .**  **Emissions Counte d as By** **- Products with and without Simplification**  **Consumption of**  **F -** **GHG (kg) Emissions of** 

**F -** **GHG over and above**  **consumption (kg)**  **Overall**

**abatement** **level (a*d)** **Abated**

**Emissions Fraction** 

**"Extra" with Simplification**  **Unabated**

**Emissions Fraction** 

**"Extra" without**  **Simplification Difference in** 

**Fractions as Share of Extra**  **without Simplification**  1 0.5 0% 1.5 33% 1.5 33% 0% 1 0.5 10% 1.35 26% 1.5 33% 22% 1 0.5 50% 0.75 0% 1.5 33% 100% 1 0.5 90% 0.15 0% 1.5 33% 100% 1 0.5 99% 0.015 0% 1.5 33% 100% 1 1 0% 2 50% 2 50% 0% 1 1 10% 1.8 44% 2 50% 11% 1 1 50% 1 0% 2 50% 100% 1 1 90% 0.2 0% 2 50% 100% 1 1 99% 0.02 0% 2 50% 100% 1 4 0% 5 80% 5 80% 0% 1 4 10% 4.5 78% 5 80% 3% 1 4 50% 2.5 60% 5 80% 25% 1 4 90% 0.5 0% 5 80% 100% 1 4 99% 0.05 0% 5 80% 100% 1 9 0% 10 90% 10 90% 0% 1 9 10% 9 89% 10 90% 1% 1 9 50% 5 80% 10 90% 11% 1 9 90% 1 0% 10 90% 100% 1 9 99% 0.1 0% 10 90% 100% As shown by Table 5, where stack systems have low abatement levels, the simplification has little impact. However, where stack systems have very high abatement levels (e.g., 90% or more), the simplification would result in no “extra” emissions being count ed as a by- product even when a substantial share (e.g., 90%) of the unabated emissions of an F - GHG actually are formed as a by- product. To ensure that all “extra” emissions were reassigned as by- products of other gases, it would be necessary to (1) C alculate the unabated emissions of the gas with the extra emissions ; (2) Assign the share of these unabated emissions that equals consumption to Equation I - 19 ;August 2012 Subpart I Stack Testing Technical Support

Page 20 of 25 (3) R eapply the abatement level to these emissions in Equation I - 19 (reducing the EF from 1.0 to a lowe r level) ; (4) R eapply the abatement level to the “extra” emissions that will be treated as a by- product in Equation I - 20 ; and (5) U se Equation I - 20 to calculate the resulting by- product factor. **5.4.2. Emission Factor Variability**  **and Uncertainty** In establishing a stack test method , the EPA took into consideration the sources of potential variability and uncertainty in EFs established at a fab. These included:  Variability of F - GHG utilization and by- product generation factors across processes : o Factors can vary over wide ranges, e.g., an order of magnitude or more. o Processes vary as the mix of particular products and their recipes varies. This mix varies over time to different extents at different facilities.  Variability in abatement levels : o Either long-term , due to in stallation or removal of abatement systems, or short -term , due to changes in abatement system uptime.  Variability in flow patterns between tools and particular stacks .  Uncertainty in gas consumption measurements . The EPA reviewed EF data developed from stack testing for March and August of 2011 for a fab owned and operated by one company (Company D) that produces a range of semiconductor products and uses an array of F - GHGs. The EFs are presented in Table 6 below. Table 6 shows that the de veloped stack EFs are generally similar for the fab between the months by gas and for the stack, showing consistency in EFs at different times of the year.August 2012 Subpart I Stack Testing Technical Support

Page 21 of 25 **Table 6**  **. Stack Test Emission Factors for a**  **Company D fab in March 2011 and August 2011 (SIA, 2012g )**  **EF Units**  **F -** **GHGs Consumed Byproducts**  **Stack** Mar- 11 **NF 3**  **CF 4**  **CHF 3**  **SF 6**  **CH 2**  **F 2**  **C 4**  **F 8**  **C 5**  **F 8**  **C 2**  **F 6**  **C 3**  **F 8**  EF (kg emit / kg use) 0.0673 0.8669 0.0591 0.312 6 0.110 8 0.057

2 0.0247 bpEF (kg emit / kg total

gas consumed) 0.0069 0.0004 % of Total Emissions percent 58.01 26.59 8.64 2.08 0.00 0.10 0.00 4.36 0.22 Stack EF mtCO2e

Emitted/mtCO2e Consumed 0.0954 Aug- 11 **NF 3**  **CF 4**  **CHF 3**  **SF 6**  **CH 2**  **F 2**  **C 4**  **F 8**  **C 5**  **F 8**  **C 2**  **F 6**  **C 3**  **F 8**  EF (kg emit / kg use) 0.0576 0.8321 0.0569 0.376 8 0.112 9 0.067 6 0.0252 bpEF (kg emit / kg total

gas consumed) 0.005 0.0039 % of Total Emissions percent 48.73 32.83 9.72 3.34 0.00 0.13 0.00 3.29 1.95 Stack EF mtCO2e

Emitted/mtCO2e Consumed 0.0936 EF Agreement % Mar - Aug EF

Diff. 14 4 4 21 2 18 2 28 875 2 The EPA is proposing certain provisions to minimize variability and uncertainty in EFs determined through stack testing : 1. T he EPA is proposing provisions to ensure accurate measurements of gas consumption during the stack test ing period (see Section 5. 2 ) . 2. T he EPA is proposing that new stack EFs be developed from testing each reporting year, unless the variability in EFs meet certain variability criteria . Section 7 of this memo describes this in more detail . 3. As described in section 5. 1.3 of this memo, the EPA is proposing provisions to ensure the representativeness of EFs by requiring that there are no changes during the testing per iod in the centralized abatement systems (if present) or stack flow configuration. **6. Estimating**  **Fab Emissions**  The proposed stack testing method would require facilities to estimate emissions from three kinds of F GHG emissions : 1) emissions of intermittent low- use gases, 2) emissions from low- emitting stack systems, and 3) emissions from stack systems and gases tested. Methods the EPA i s proposing for estimating each of these types of emissions are described below. 1. Emissions o f intermittent low- use F - GHGs The EPA is proposing that emissions of intermittent low- use F - GHGs be estimated using a modification of the 2006 IPCC Tier 2a method. F abs would be required to use the same EFs as used to determin eAugust 2012 Subpart I Stack Testing Technical Support

Page 22 of 25 whether an F - GHG meets the i ntermittent low- use criteria (see Section 4 and discussion in the paragraph below on Tier 2a EFs ) , but would require the use of actual data for the current reporting year, including;  F ab abatement system uptime calculated as the complement of the downtime estimated per the methods described in Section 5 .3 ;  W eighted - average fab -wide DRE s, based on either default DRE values or actual measured DRE values; 27  A nnual consumption of the intermittent low- use F - GHG, calculated per the provisions in su bpart I based on a mass balance method , 28 and ;  The fraction of the intermittent low- use F - GHG used in tools with abatement systems as estimated by the fab . The EPA is proposing that semiconductor manufacturers rely on new (since the 2006 IPCC Guidelines) Ti er 2a EFs, which are based on emissions data supporting the default etch EF method (see Technical Support for Modifications to the Fluorinated Greenhouse Gas Emission Estimation Method Option for Semiconductor Facilities under Subpart I ). For micro - electro - mechanical systems (MEMS) manufacturers, the EPA is proposing using the Tier 2a EFs for semiconductor manufacturing provided in the 2006 IPCC Guidelines because the manufacturing processes are very similar. The EPA is not currently upd ating the MEMS EFs based on any additional semiconductor data beyond what is in the 2006 IPCC Guidelines, because these devices are generally manufactured on older semiconductor manufacturing tools (i.e., 150 mm and 200 mm wafer sizes) and are just startin g to move into manufacturing on newer tools (i.e., 300 mm). Without any additional data on emissions from MEMS processes, it was not feasible for the EPA to propose revised EFs for MEMS processes. The EPA is proposing that other electronics manufactures (l iquid crystal displays (LCDs) and photovoltaic (PV) cell manufacturers) use Tier 2a EFs that are the same as those provided in the 2006 IPCC Guidelines. 2. E missions from “low- emitting stack systems” The EPA is proposing that emissions from low - emitting stac k systems for reporting purposes be estimated using a Tier 2a method , again using the same EFs as used for determining whether a stack system is considered to be “low- emitting” and exempt from testing, and also using actual data from the current reporting year as described for intermittent low- use F - GHGs, above . However, when estimating emissions from low- emitting stack systems, a fab would also need to apportion the amount of F - GHG s consumed to low- emitting stack systems. The EPA is proposing that this be done using an apportioning model subject to the same apportioning model verification require ments as for apportioning gas

27 Default abatement system destruction or removal efficiencies are provided in subpart I by gas and process type (see Technical Support for Accounting for Destruction or Removal Efficiency for Electronics Manufacturing Fa cilities under Subpart I ). However the Tier 2a method does not distinguish by process type. Therefore the EPA is proposing that a fab estimate an average DRE for each gas using the provided default DREs (or fab - specific measured DREs) and weights based on the consumption of the gas at the fab by process type. 28 The methods for estimating annual gas consumption for stack testing are the same as the method required when using a default EF - based method.August 2012 Subpart I Stack Testing Technical Support

Page 23 of 25 consumption for other purposes in subpart I (e.g., apportioning gas usage to process types/sub -types and for the fraction used in tools with or without abatement systems). 3. Emissions based on a gas and fab - specific EF The third and final type of emissions that the EPA is proposing to require to be estimated for the stack test method are those that are based on the gas - and fab - speci fic EFs develop ed from stack tests using the methods being proposed by the EPA and described in this document. Using the calculation methods proposed by the EPA, estimating these types of emissions would require the same current reporting year data used fo r estimating emissions from low- emitting stack systems and intermittent low- use F GHGs, with the exception that F - GHG consumption would be apportioned to the stack systems that are tested (in aggregate) and the gas - and fab - specific developed stack EFs. **7. St** **ack Testing Frequency** Table 7 below presents the proposed stack testing frequency requirements and the rationale for the proposed frequencies. **Table 7**  **. Proposed Stack Testing Frequency Requirements and Supporting Rationale**  **Proposed Requirement Rationale**  **Initial Testing** Facilities would conduct three sets of test s of each stack system subject to testing, at a minimum of one test per year for three years . If they chose to do so, facilities can conduct more than one test per year, but each set of emissions testing would be separated by at least 2 months. The purpose of the initial testing is to determine the variability of stack EFs between tests . The variability in emissions based on the initial three tests would determine the frequency at which subsequent testing will need to be done. **Subsequent Testing** After 3 sets of emissions testing are completed, if the relative standard deviation (RSD) of the CO 2 e EFs calculated from each of the 3 tests is ≤15% and the RSD for all single F - GHG EFs that individually account for 5% or more of CO 2 e emissions is ≤ 20%, a reporter c ould use the arithmetic average of the three EF for calculating F - GHG emissions and defer testing for the next 4 years (unless a re -test is triggered). If the variability of the stack EFs is low, as indicated by the results of the RSD analysis , then testing would not need to be performed as frequently. However, if a particular facility has varying EFs due , for example , to changes in the type of products being manufactured, then testing would need to be more frequent. The reporter would conduct an annual test, at a minimum, in the 5th year following the last stack test and repeat the RSD evaluation using the data from the three most recent tests . If the RSD criteria are not met, the reporter would continue testing annually at a minimum (but at least 2 months apart) and repeat the RSD analysis using the previous three sets of data. This provision has been included in the proposal to ensure that the EFs determined from stack testing are representative of current operations and emissions . The reporter could do three t ests in one year and try to meet the RSD criteria, but if they do not qualify to skip testing, they would still need to do annual testing beginning in the next year. If multiple sets of testing are done in one year, the average of those sets would be used for the annual report. This provision is being proposed so that annual emission testing would still be required when the three initial tests are conducted in the first year and the results show that emissions are too variable to meet the criteria that woul d allow the facility to skip testing .August 2012 Subpart I Stack Testing Technical Support

Page 24 of 25 **8. Changes at a Fab That Would**  **Trigger Re** **- testing of Stack Systems**  Data provided by SIA for various changes at a fab betwe en 2009 and 2010 have demonstrated that c hanges in the mix of F - GHG and by- product precursors and in manufacturing processes can affect F GHG emissions at the stack (see SIA, 2011 ). Because such changes would require that EF s developed from stack measurements would need to be kept up to date , the EPA, with input from SIA, developed and is proposing va rious crit eria that would trigger re -testing of stack systems to revise EF s if the fab had previously qualified to skip annual testing . These criteria would not trigger a re -test if a facility is conducting annual testing. The proposed criteria for determining if a stack system would have to be re te sted are described below:  C onsumption of a specific F - GHG used during the stack test changes by more than 10 percent of total annual gas consumption in CO 2 e, relative to gas consumption in CO 2 e for that g as during the year in which the most recent emissions test s were conducted. For example, if the use of a single F - GHG goes from 25 percent of total fab F - GHG consumption in CO 2 e to more than 35 percent of total fab F - GHG consumption in CO 2 e, that would tri gger the need for a new test.  A change in the use of an intermittent low- use gas that was not used during the emissions test and not reflected in the fab - specific EF, such that it no longer meets the proposed definition of an intermittent low- use gas ( see Section 4) .  A decrease by more than 10 percent in the fraction of tools with abatement systems, compared to the fraction of tools with abatement systems during the most recent emissions test.  A change in the wafer size used by the fab since the most re cent emissions test . 29  A change in a stack system that formerly met the criteria for being a low- emitting stack not subject to testing, such that it no longer meets those criteria. If any of these criteria are met, a fab would be required to re -test the stack systems and develop new F GHG - specific and fab - specific EF s per the methods described in S ection 5 . **9. References**  Intel (20 10 ). Comments from Intel Corporation. Re: Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs: Propose d Rulemaking 75 Fed. Reg. 18652 (Apr. 12, 2010) . Available in EPA docket EPA- HQ- OAR - 2009 - 0927. IPCC (2006). 2006 IPCC Guidelines for National Greenhouse Gas Inventories . The National Greenhouse Gas Inventories Programme, The Intergovernmental Panel on Clim ate Change, H.S. Eggleston, L. Buendia, K. Miwa, T Ngara, and K. Tanabe (eds.). Hayama, Kanagawa, Japan. Available at: http://www.ipcc - nggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_6_Ch6_Electronics_Industry.pdf. SIA (2011). SIA/ ISMI Presentation on St ack Testing Alternative , November 30, 2011. Available in EPA docket EPA- HQ- OAR - 2011 -0028.

29 By looking at the difference in default EFs developed f rom measured emissions data for fabs of various wafer sizes (SIA, 2012b and EPA, 2010) it is apparent that the process changes associated with transitioning to a different wafer size will likely result in changes in fab emissions.August 2012 Subpart I Stack Testing Technical Support

Page 25 of 25 SIA (2012a). Report to EPA on Etch Factor Proposal for Fab GHG Emissions Reporting, February 28, 2012. Available in EPA docket EPA- HQ- OAR - 2011 - 0028. SIA (2012b). International SEMATECH Manufacturing Initiative Environmental Safety and Health Technology Center Etch Process Equipment Emissions Characterization Data (120228 etch report to EPA.xls), February 6, 2012. Available in EPA docket EPA- HQ- OAR - 2011 - 0028. SIA (2 012c). Measured Gas Usage Rates During Stack Testing, April 28, 2012. Available in EPA docket EPA- HQ- OAR - 2011 -0028. SIA (2012d). Proposal for Dealing with Low Emissions Stack Systems that Will be Excluded from Testing Under the Stack Test Option, March 27, 2012. Available in EPA docket EPA- HQ- OAR - 2011 -0028. SIA (2012e). Response to EPA’s Stack Test Questions, March 27, 2012. Available in EPA docket EPA- HQOAR - 2011 - 0028. SIA (2012f). SIA Briefing Paper on Abatement Issues: Destruction Removal Efficiency (DRE) (Appendix 7 - 120110 SIA abatement briefing paper.pdf), January 10, 2012. Available in EPA docket EPA- HQ- OAR 2011 -0028. SIA (2012g). Response to EPA’s Stack Test Question 1. March 7, 2012. Available in EPA docket EPA- HQOAR - 2011 - 0028. SIA (2012h). Intermittent Low/High Use Gas Criteria for Subpart I. April 27, 2012. Available in EPA docket EPA- HQ- OAR - 2011 -0028. U.S. EPA (2010). Draft EFs for Refined Semiconductor Manufacturing Process Categories. United States Environmental Protection Agency, EPA- HQ- OAR - 2009 - 0927 -0073. May, 2010.