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(a) Application. You may use a chemiluminescent detector (CLD) to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept a CLD for NOX measurement, even though it measures only NO and NO2, when coupled with an NO2-to-NO converter, since conventional engines and aftertreatment systems do not emit significant amounts of NOX species other than NO and NO2. Measure other NOX species if required by the standard-setting part. While you may also use other instruments to measure NOX, as described in §1065.272, use a reference procedure based on a chemiluminescent detector for comparison with any proposed alternate measurement procedure under §1065.10.
(b) Component requirements. We recommend that you use a CLD that meets the specifications in Table 1 of §1065.205. Note that your CLD-based system must meet the quench verification in §1065.370 and it must also meet the linearity verification in §1065.307. You may use a heated or unheated CLD, and you may use a CLD that operates at atmospheric pressure or under a vacuum.
(c) NO2-to-NO converter. Place upstream of the CLD an internal or external NO2-to-NO converter that meets the verification in §1065.378. Configure the converter with a bypass line if it is needed to facilitate this verification.
(d) Humidity effects. You must maintain all CLD temperatures to prevent aqueous condensation. If you remove humidity from a sample upstream of a CLD, use one of the following configurations:
(1) Connect a CLD downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in §1065.378.
(2) Connect a CLD downstream of any dryer or thermal chiller that meets the verification in §1065.376.
(e) Response time. You may use a heated CLD to improve CLD response time.
[70 FR 40516, July 13, 2005, as amended at 73 FR 37300, June 30, 2008; 76 FR 57442, Sept. 15, 2011; 79 FR 23761, Apr. 28, 2014; 89 FR 29796, Apr. 22, 2024]
(a) Application. You may use a nondispersive ultraviolet (NDUV) analyzer to measure NOX concentration in raw or diluted exhaust for batch or continuous sampling. We generally accept an NDUV for NOX measurement, even though it measures only NO and NO2, since conventional engines and aftertreatment systems do not emit significant amounts of other NOX species. Measure other NOX species if required by the standard-setting part. Note that good engineering judgment may preclude you from using an NDUV analyzer if sampled exhaust from test engines contains oil (or other contaminants) in sufficiently high concentrations to interfere with proper operation.
(b) Component requirements. We recommend that you use an NDUV analyzer that meets the specifications in Table 1 of §1065.205. Note that your NDUV-based system must meet the verifications in §1065.372 and it must also meet the linearity verification in §1065.307.
(c) NO2-to-NO converter. If your NDUV analyzer measures only NO, place upstream of the NDUV analyzer an internal or external NO2-to-NO converter that meets the verification in §1065.378. Configure the converter with a bypass to facilitate this verification.
(d) Humidity effects. You must maintain NDUV temperature to prevent aqueous condensation, unless you use one of the following configurations:
(1) Connect an NDUV downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in §1065.378.
(2) Connect an NDUV downstream of any dryer or thermal chiller that meets the verification in §1065.376.
[70 FR 40516, July 13, 2005, as amended at 73 FR 59323, Oct. 8, 2008; 76 FR 57442, Sept. 15, 2011; 79 FR 23761, Apr. 28, 2014; 89 FR 29796, Apr. 22, 2024]
(a) Application. You may use a zirconia oxide (ZrO 2) analyzer to measure NO X in raw exhaust for field-testing engines.
(b) Component requirements. We recommend that you use a ZrO 2 analyzer that meets the specifications in Table 1 of §1065.205. Note that your ZrO 2 -based system must meet the linearity verification in §1065.307.
(c) Species measured. The ZrO 2 -based system must be able to measure and report NO and NO 2 together as NO X . If the ZrO 2 -based system cannot measure all of the NO 2 , you may develop and apply correction factors based on good engineering judgment to account for this deficiency.
(d) Interference. You must account for NH 3 interference with the NO X measurement.
[88 FR 4673, Jan. 24, 2023]
(a) General component requirements. We recommend that you use an analyzer that meets the specifications in Table 1 of §1065.205. Note that your system must meet the linearity verification in §1065.307.
(b) Instrument types. You may use any of the following analyzers to measure N2O:
(1) Nondispersive infrared (NDIR) analyzer.
(2) Fourier transform infrared (FTIR) analyzer. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 in 40 CFR part 63, appendix A, and ASTM D6348 (incorporated by reference, see §1065.1010) are considered valid methods for spectral interpretation.
(3) Laser infrared analyzer. Examples of laser infrared analyzers are pulsed-mode high-resolution narrow band mid-infrared analyzers, and modulated continuous wave high-resolution narrow band mid-infrared analyzers.
(4) Photoacoustic analyzer. Use an optical wheel configuration that gives analytical priority to measurement of the least stable components in the sample. Select a sample integration time of at least 5 seconds. Take into account sample chamber and sample line volumes when determining flush times for your instrument.
(5) Gas chromatograph analyzer. You may use a gas chromatograph with an electron-capture detector (GC-ECD) to measure N2O concentrations of diluted exhaust for batch sampling.
(i) You may use a packed or porous layer open tubular (PLOT) column phase of suitable polarity and length to achieve adequate resolution of the N2O peak for analysis. Examples of acceptable columns are a PLOT column consisting of bonded polystyrene-divinylbenzene or a Porapack Q packed column. Take the column temperature profile and carrier gas selection into consideration when setting up your method to achieve adequate N2O peak resolution.
(ii) Use good engineering judgment to zero your instrument and correct for drift. You do not need to follow the specific procedures in §§1065.530 and 1065.550(b) that would otherwise apply. For example, you may perform a span gas measurement before and after sample analysis without zeroing and use the average area counts of the pre-span and post-span measurements to generate a response factor (area counts/span gas concentration), which you then multiply by the area counts from your sample to generate the sample concentration.
(c) Interference verification. Certain compounds can positively interfere with NDIR, FTIR, laser infrared analyzers, and photoacoustic analyzers by causing a response similar to N 2 O. Perform interference verification for NDIR, FTIR, laser infrared analyzers, and photoacoustic analyzers using the procedures of §1065.375. Interference verification is not required for GC-ECD. Perform interference verification for the following interference species:
(1) The interference species for NDIR analyzers are CO, CO 2 , H 2 O, CH 4 , and SO 2 . Note that interference species, with the exception of H 2 O, are dependent on the N 2 O infrared absorption band chosen by the instrument manufacturer. For each analyzer determine the N 2 O infrared absorption band. For each N 2 O infrared absorption band, use good engineering judgment to determine which interference species to evaluate for interference verification.
(2) Use good engineering judgment to determine interference species for FTIR and laser infrared analyzers. Note that interference species, with the exception of H 2 O, are dependent on the N 2 O infrared absorption band chosen by the instrument manufacturer. For each analyzer determine the N 2 O infrared absorption band. Determine interference species under this paragraph (c)(2) that are appropriate for each N 2 O infrared absorption band, or you may identify the interference species based on the instrument manufacturer's recommendations.
(3) The interference species for photoacoustic analyzers are CO, CO 2 , and H 2 O.
[74 FR 56512, Oct. 30, 2009, as amended at 76 FR 57443, Sept. 15, 2011; 78 FR 36398, June 17, 2013;79 FR 23761, Apr. 28, 2014; 81 FR 74163, Oct. 25, 2016; 86 FR 34536, Jun. 29, 2021; 89 FR 29796, Apr. 22, 2024]
(a) General component requirements. We recommend that you use an analyzer that meets the specifications in §1065.205. Note that your system must meet the linearity verification in §1065.307.
(b) Instrument types. You may use any of the following analyzers to measure NH 3 :
(1) Nondispersive ultraviolet (NDUV) analyzer.
(2) Fourier transform infrared (FTIR) analyzer. Use appropriate analytical procedures for interpretation of infrared spectra. For example, EPA Test Method 320 (see §1065.266(c)) and ASTM D6348 (incorporated by reference, see §1065.1010) are considered valid methods for spectral interpretation.
(3) Laser infrared analyzer. Examples of laser infrared analyzers are pulsed-mode high-resolution narrow-band mid-infrared analyzers, modulated continuous wave high-resolution narrow band near and mid-infrared analyzers, and modulated continuous-wave high-resolution near-infrared analyzers. A quantum cascade laser, for example, can emit coherent light in the mid-infrared region where NH 3 and other nitrogen compounds can effectively absorb the laser's energy.
(c) Sampling system. Minimize NH 3 losses and sampling artifacts related to NH 3 adsorbing to surfaces by using sampling system components (sample lines, prefilters and valves) made of stainless steel or PTFE heated to (110 to 202) °C. If surface temperatures exceed ≥130 °C, take steps to prevent any DEF in the sample gas from thermally decomposing and hydrolyzing to form NH 3 . Use a sample line that is as short as practical.
(d) Interference verification. Certain species can positively interfere with NDUV, FTIR, and laser infrared analyzers by causing a response similar to NH 3 . Perform interference verification as follows:
(1) Perform SO 2 and H 2 O interference verification for NDUV analyzers using the procedures of §1065.372, replacing occurances of NO X with NH 3 . NDUV analyzers must have combined interference that is within (0.0 ±2.0) µmol/mol.
(2) Perform interference verification for FTIR and laser infrared analyzers using the procedures of §1065.377. Use good engineering judgment to determine interference species. Note that interference species, with the exception of H 2 O, are dependent on the NH 3 infrared absorption band chosen by the instrument manufacturer. Determine interference species under this paragraph (d)(2) that are appropriate for each NH 3 infrared absorption band, or you may identify the interference species based on the instrument manufacturer's recommendations.
[89 FR 29797, Apr. 22, 2024]