On May 22, 2008, the EPA published a final rule in the Federal Register that made technical corrections to five test methods. Inadvertent printing errors were made in the publication. Text insertions were misplaced, duplicate insertions were made, and the definition for system bias was inadvertently revised. On Friday, the agency re-released the test method changes, with corrections.

The revised version of the pertinent section (Method 3A, Section 7.1) is below:

PART 60--STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES

Method 3A--Determination of Oxygen and Carbon Dioxide Concentrations in Emissions From Stationary Sources (Instrumental Analyzer Procedure)

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7.1 Calibration Gas. What calibration gasses do I need? Refer to Section 7.1 of Method 7E for the calibration gas requirements. Example calibration gas mixtures are listed below. Precleaned or scrubbed air may be used for the O₂ high-calibration gas provided it does not contain other gases that interfere with the O₂ measurement. (a) CO₂ in nitrogen (N₂).
(b) CO₂ in air.
(c) CO₂/SO₂ gas mixture in N₂.
(d) O₂/SO₂ gas mixture in N₂.
(e) O₂/CO₂/SO₂ gas mixture in N₂.
(f) CO₂/NO_X gas mixture in N₂.
(g) CO₂/SO₂/NO_X gas mixture in N₂.

The tests for analyzer calibration error and system bias require high-, mid-, and low-level gases.

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Appendix A-4-- [Amended]

3. Method 7E is amended as follows:
a. By revising section 3.12.
b. By revising section 3.16.
c. By revising section 7.1.
d. By revising section 8.1.2.
e. By revising section 8.2.1.
f. By revising section 8.2.4.
g. By revising the Summary Table of QA/QC in Section 9.0.
h. By revising section 12.11.
i. By revising section 16.2.2.

Method 7E--Determination of Nitrogen Oxides Emissions From Stationary Sources (Instrumental Analyzer Procedure)

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3.12 Low-Concentration Analyzer means any analyzer that operates with a calibration span of 20 ppm NO_X or lower. Each analyzer model used routinely to measure low NO_X concentrations must pass a manufacturer's stability test (MST). An MST subjects the analyzer to a range of line voltages and temperatures that reflect potential field conditions to demonstrate its stability following procedures similar to those provided in 40 CFR 53.23. Ambient-level analyzers are exempt from the MST requirements of Section 16.3. A copy of this information must be included in each test report. Table 7E-5 lists the criteria to be met.

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3.16 System Bias means the difference between a calibration gas measured in direct calibration mode and in system calibration mode. System bias is determined before and after each run at the low- and mid- or high-concentration levels. For dilution-type systems, pre- and post-run system calibration error is measured rather than system bias.

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7.1 Calibration Gas. What calibration gases do I need? Your calibration gas must be NO in N₂ and certified (or recertified) within an uncertainty of 2.0 percent in accordance with "EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards" September 1997, as amended August 25, 1999, EPA-600/R-97/121. Blended gases meeting the Traceability Protocol are allowed if the additional gas components are shown not to interfere with the analysis. If a zero gas is used for the low-level gas, it must meet the requirements under the definition for "zero air material" in 40 CFR 72.2. The calibration gas must not be used after its expiration date. Except for applications under part 75 of this chapter, it is acceptable to prepare calibration gas mixtures from EPA Traceability Protocol gases in accordance with Method 205 in appendix M to part 51 of this chapter. For part 75 applications, the use of Method 205 is subject to the approval of the Administrator. The goal and recommendation for selecting calibration gases is to bracket the sample concentrations. The following calibration gas concentrations are required:

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8.1.2 Determination of Stratification. Perform a stratification test at each test site to determine the appropriate number of sample traverse points. If testing for multiple pollutants or diluents at the same site, a stratification test using only one pollutant or diluent satisfies this requirement. A stratification test is not required for small stacks that are less than 4 inches in diameter. To test for stratification, use a probe of appropriate length to measure the NO_X (or pollutant of interest) concentration at twelve traverse points located according to Table 1-1 or Table 1-2 of Method 1. Alternatively, you may measure at three points on a line passing through the centroidal area. Space the three points at 16.7, 50.0, and 83.3 percent of the measurement line. Sample for a minimum of twice the system response time (see Section 8.2.6) at each traverse point.

Calculate the individual point and mean NO_X concentrations. If the concentration at each traverse point differs from the mean concentration for all traverse points by no more than: (a) ±5.0 percent of the mean concentration; or (b) ±0.5 ppm (whichever is less restrictive), the gas stream is considered unstratified and you may collect samples from a single point that most closely matches the mean. If the 5.0 percent or 0.5 ppm criterion is not met, but the concentration at each traverse point differs from the mean concentration for all traverse points by no more than: (a) ±10.0 percent of the mean; or (b) ±1.0 ppm (whichever is less restrictive), the gas stream is considered to be minimally stratified, and you may take samples from three points. Space the three points at 16.7, 50.0, and 83.3 percent of the measurement line.

Alternatively, if a twelve-point stratification test was performed and the emissions were shown to be minimally stratified (all points within ±10.0 percent of their mean or within ±1.0 ppm), and if the stack diameter (or equivalent diameter, for a rectangular stack or duct) is greater than 2.4 meters (7.8 ft), then you may use 3-point sampling and locate the three points along the measurement line exhibiting the highest average concentration during the stratification test, at 0.4, 1.0 and 2.0 meters from the stack or duct wall. If the gas stream is found to be stratified because the 10.0 percent or 1.0 ppm criterion for a 3-point test is not met, locate twelve traverse points for the test in accordance with Table 1-1 or Table 1-2 of Method 1.

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8.2.1 Calibration Gas Verification. How must I verify the concentrations of my calibration gases? Obtain a certificate from the gas manufacturer documenting the quality of the gas. Confirm that the manufacturer certification is complete and current. Ensure that your calibration gas certifications have not expired. This documentation should be available on-site for inspection. To the extent practicable, select a high-level gas concentration that will result in the measured emissions being between 20 and 100 percent of the calibration span.

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8.2.4 NO₂ to NO Conversion Efficiency Test. Before or after each field test, you must conduct an NO₂ to NO conversion efficiency test if your system converts NO₂ to NO before analyzing for NO_X. You may risk testing multiple facilities before performing this test provided you pass this test at the conclusion of the final facility test. A failed final conversion efficiency test in this case will invalidate all tests performed subsequent to the test in which the converter efficiency test was passed. Follow the procedures in Section 8.2.4.1, or 8.2.4.2. If desired, the converter efficiency factor derived from this test may be used to correct the test results for converter efficiency if the NO₂ fraction in the measured test gas is known. Use Equation 7E-8 in Section 12.8 for this correction.

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9.0 Quality Control * * *