however. the leak check is optional.

3.3 Place the probe in the stack, with the tip of the probe positioned at the sampling point: purge the sampling line long enough to allow at least five exchanges. Draw a sample into the analyzer, and immediately analyze it for percent CO2 and percent O2. Determine the percentage of the gas that is N 2 and CO by subtracting the sum of the percent CO₂ and percent 0₂ 0 from 100 percent. Calculate the dry molecular weight as indicated in Section 7.2. 3.4 Repeat the sampling. analysis. and calculation procedures until the dry molecular weights of any three grab samples differ from their mean by no more than 0.3 g/g- mole (0.3 1b/lb-mole). Average these three molecular weights, and report the results to the nearest 0.1 g/g-mole (0.1 lb/Ib-mole). 4. SINGLE-POINT, INTEGRATED SAMPLING AND ANALYTICAL PROCEDURE 4.1 The sampling point in the duct shall be located as specified in Section 3.1. 4.2 Leak check (optional) the flexible bag as in Section 2.2.6. Set up the equipment as shown in Figure 3-2. Just before sampling. leak check (optional) the train by placing a vacuum gauge at the condenser inlet. pulling a vacuum of at least 250 mm Hg (10 In. Hg). plugging the outlet at the quick disconnect, and then turning off the pump. The vacuum should remain stable for at least 0.5 minute. Evacuate the flexible bag. Connect the probe, and place it in the stack, with the tip of the probe positioned at the sampling point: purge the sampling line. Next. connect the bag. and make sure that all connections are tight. 4.3 Sample at a constant rate. The sampling run should be simultaneous with, and for the same total length of time as, the pollutant emission rate determination. Collection of at least 30 liters (1.00 ft 3) of sample gas is recommended; however, smaller volumes may be collected, If desired. 4.4 Obtain one integrated flue gas sample during each pollutant emission rate determination. Within 8 hours after the sample is taken, analyze it for percent CO₂ and percent O₂ using either an Orsat analyzer or a Fyrite type combustion gas analyzer. If an Orsat analyzer is used. It is recommended that Orsat leak check described in Section 6, be performed before this determination; however, the check is optional. Determine the percentage of the gas that is N₂ and CO by subtracting the sum of the percent CO₂ and percent 0 from 100 percent. Calculate the dry molecular weight as indicated in Section 7.2. 4.5 Repeat the analysis and calculation procedures until the individual dry molecular weights for any three analyses differ from their mean by no more than 0.3 g/g- mole (0.3 lb/lb-mole). Average these three molecular weights, and report the results to the nearest 0.1 g/g-mole (0.1 lb/lb-mole). 5. MULTI-POINT, INTEGRATED SAMPLING AND ANALYTICAL PROCEDURE 5.1 Unless otherwise specified by the Administrator, a minimum of eight traverse points shall be used for circular stacks having diameters less than 0.61 m (24 in.). a minimum of nine shall be used for rectangular stacks having equivalent diameters less than 0.61 m (24 in.). and a minimum of 12 traverse points shall be used for all other cases. The traverse points shall be located according to Method 1. The use of fewer points is subject to approval of the Administrator. 5.2 Follow the procedures outlined in Sections 4.2 through 4.5. except for the following: Traverse all sampling points, and sample at each point for an equal length of time. Record sampling data as shown in Figure 3-3. Time Traverse pt. Q. liter/min % dav." Average *% X 100 (Must be s10%) METHOD 3A 40 CFR PART 60 APPENDIX A Pt. 60, App. A, Meth. 3A Figure 3-3. Sampling rate data. 6. LEAK-CHECK PROCEDURE FOR ANALYZER Moving an Orsat analyzer frequently causes It to leak. Therefore. an Orsat analyzer should be thoroughly leak checked on site before the flue gas sample is introduced into It. The procedure for leak checking an Orsat analyzer is as follows: 6.1 Bring the liquid level in each pipette up to the reference mark on the capillary tubing. and then close the pipette stopcock. 6.2 Raise the leveling bulb sufficiently to bring the confining liquid meniscus onto the graduated portion of the burette, and then close the manifold stopcock. 6.3 Record the meniscus position. 6.4 Observe the menisus in the burette and the liquid level in the pipette for movement over the next 4 minutes. 6.5 For the Orsat analyzer to pass the leak check, two conditions must be met: 6.5.1 The liquid level in each pipette must not fall below the botton of the capillary tubing during this 4-minute interval. 6.5.2 The menisus in the burette must not change by more than 0.2 ml during this 4- minute interval. 6.6 If the anlyzer fails the leak-check procedure. check all rubber connections and stopcocks to determine whether they might be the cause of the leak. Disassemble, clean, and regrease leaking stopcocks. Replace leaking rubber connections. After the analyzer is reassembled, repeat the lead-check procedure. 7. CALCULATIONS 7.1 Nomenclature Ma = Dry molecular weight, g/g-mole (1b/1b- mole). %CO₂ = Percent CO2 by volume, dry basis. %O₂ = Percent O₂ by volume. dry basis. %CO = Percent CO by volume, dry basis. %N₂ - Percent N₂ by volume, dry basis. 0.280 - Molecular weight of N₂ or CO. divided by 100. 0.320 - Molecular wight of O2 divided by 100. 0.440 = Molecular weight of CO2 divided by 100. 7.2 Dry Molecular Weight. Use Equation 3- 1 to calculate the dry molecular weight of the stack gas. Md - 0.440(%CO₂) + 0.320 (%0 2) + 0.280(%N₂ + %CO) Eq. 3-1 NOTE. The above equation does not consider argon in air (about 0.9 percent, molecular weight of 39.9). A negative error of about 0.4 percent is introduced. The tester may choose to include argon in the analysis using procedures subject to approval of the Administrator. 8. BIBLIOGRAPHY ORSATl. Altshuller, A.P. Storage of Gases and Vapors in Plastic Bags. International Journal of Air and Water Pollution. 6:75-81. 1963. 2. Conner, William D. and J.S. Nader. Air Sampling with Plastic Bags. Journal of the American Industrial Hyglene Association. 25.292-297. 1964. 3. Burrell Manual for Gas Analysts, Seventh edition. Burrell Corporation, 2223 Fifth Avenue, Pittsburgh, PA. 15219. 1951. 4. Mitchell. W.J. and M.R. Midgett. Field Reliability of the Orsat Analyzer. Journal of Air Pollution Control Association. 26:491-495. May 1976. 5. Shigehara, R.T., R. M. Neulicht, and W.S. Smith. Validating Orsat Analysis Data from Fossil Fuel-Fired Units. Stack Sampling News. 4(2):21-26. August 1976. METHOD 3A-DETERMINATION OF OXYGEN AND CARBON DIOXIDE CONCENTRATIONS IN EMIS- SIONS FROM STATIONARY SOURCES (INSTRU- MENTAL ANALYZER PROCEDURE) 1. Applicability and Principle 1.1 Applicability. This method is applicable to the determination of oxygen (O₂) and carbon dioxide (CO₂) concentrations in emissions from stationary sources only when specified within the regulations. 1.2 Principle. A sample is continuously extracted from the effluent stream: a portion of the sample stream is conveyed to an instrumental analyzer(s) for determination of O₂ and CO2 concentration(s). Performance specifications and test procedures are provided to ensure reliable data. 2. Range and Sensitivity Same as Method 6C, Sections 2.1 and 2.2, except that the span of the monitoring system shall be selected such that the average O2 or CO2 concentration is not less than 20 percent of the span. 3. Definitions 3.1 Measurement System. The total equipment required for the determination of the O₂ or CO₂ concentration. The measurement system consists of the same major subsystems as defined in Method 6C, Sections 3.1.1. 3.1.2. and 3.1.3. 3.2 Span, Calibration Gas, Analyzer Callbration Error, Sampling System Bias, Zero Drift, Calibration Drift, Response Time. and Calibration Curve. Same as Method 6C. Sections 3.2 through 3.8, and 3.10. 3.3 Interference Response. The output response of the measurement system to a component in the sample gas, other than the gas component being measured. 4. Measurement System Performance Specifications Same as Method 6C. Sections 4.1 through 4.4. 5. Apparatus and Reagents Environmental Protection Agency, EPA Pt. 60, App. A, Meth. 3A 5.1 Measurement System. Any measurement system for O₂ or CO₂ that meets the specifications of this method. A schematic of an acceptable measurement system is shown in Figure 6C-1 of Method 6C. The essential components of the measurement system are described below: 5.1.1 Sample Probe. A leak-free probe, of sufficient length to traverse the sample points. 5.1.2 Sample Line. Tubing, to transport the sample gas from the probe to the moisture removal system. A heated sample line is not required for systems that measure the O₂ or CO₂ concentration on a dry basis, or transport dry gases. 5.1.3 Sample Transport Line, Calibration Value Assembly. Moisture Removal System, Particulate Filter, Sample Pump. Sample Flow Rate Control, Sample Gas Manifold, and Data Recorder. Same as Method 6C, Sections 5.1.3 through 5.1.9. and 5.1.11, except that the requirements to use stainless steel. Teflon, and nonreactive glass filters do not apply. 5.1.4 Gas Analyzer. An analyzer to determine continuously the O₂ or CO2 concentration in the sample gas stream. The analyzer shall meet the applicable performance specifications of Section 4. A means of controlling the analyzer flow rate and a device for determining proper sample flow rate (e.g., precision rotameter, pressure gauge downstream of all flow controls, etc.) shall be provided at the analyzer. The requirements for measuring and controlling the analyzer flow rate are not applicable if data are presented that demonstrate the analyzer is insensitive to flow variations over the range encountered during the test. 5.2 Calibration Gases. The calibration gases for CO₂ analyzers shall be CO2 in N₂ or CO₂ in air. Alternatively. CO₂/SO₂ O₂/SO₂ or O₂/CO₂/SO₂ gas mixtures in N₂ may be used. Three calibration gases, as specified Section 5.3.1 through 5.3.3 of Method 6C. shall be used. For O₂ monitors that cannot analyze zero gas, a calibration gas concentration equivalent to less than 10 percent of the span may be used in place of zero gas. 6. Measurement System Performance Test Procedures Perform the following procedures before measurement of emissions (Section 7). 6.1 Calibration Concentration Verification. Follow Section 6.1 of Method 6C, except If calibration gas analysis is required, use Method 3 and change the acceptance criteria for agreement among Method 3 results to 5 percent (or 0.2 percent by volume, whichever is greater). 6.2 Interference Response. Conduct an interference response test of the analyzer prior to Its initial use in the field. Thereafter, recheck the measurement system If changes are made in the instrumentation that could alter the interference response (e.g., changes in the type of gas detector). Conduct the interference response in accordance with Section 5.4 of Method 20. 6.3 Measurement System Preparation. Analyzer Calibration Error, and Sampling System Bias Check. Follow Sections 6.2 through 6.4 of Method 6C. 7. Emission Test Procedure 7.1 Selection of Sampling Site and Sampling Points. Select a measurement site and sampling points using the same criteria that are applicable to tests performed using Method 3. 7.2 Sample Collection. Position the sampling probe at the first measurement point, and begin sampling at the same rate as used during the sampling system bias check. Maintain constant rate sampling (i.e., +10 percent) during the entire run. The sampling time per run shall be the same as for tests conducted using Method 3 plus twice the system response time. For each run, use only those measurements obtained after twice the response time of the measurement system has elapsed to determine the average effluent concentration. 7.3 Zero and Calibration Drift Test. Follow Section 7.4 of Method 6C. 8. Quality Control Procedures The following quality control procedures are recommended when the results of this method are used for an emission rate correction factor, or excess air determination. The tester should select one of the following options for validating measurement results: 8.1 If both O₂ and CO₂ are measured using Method 3A, the procedures described In Section 4.4 of Method 3 should be followed to validate the O₂ and CO2 measurement results. 8.2 If only O₂ is measured using Method 3A. measurements of the sample stream CO2 concentration should be obtained at the sample by-pass vent discharge using an Orsat or Fyrite analyzer. or equivalent. Duplicate samples should be obtained concurrent with at least one run. Average the duplicate Orsat or Fyrite analysis results for each run. Use the average CO2 values for comparison with the O₂ measurements in accordance with the procedures described in Section 4.4 of Method 3. 8.3 If only CO2 is measured using Method 3A, concurrent measurements of the sample stream CO2 concentration should be obtained using an Orsat or Fyrite analyzer as described in Section 8.2. For each run, differences greater than 0.5 percent between the Method 3A results and the average of the duplicate Fyrite analysis should be investigated. 9. Emission Calculation For all CO₂ analyzers, and for O₂ analyzers that can be calibrated with zero gas, follow Pt. 60, App. A, Meth. 3B