86.1338-2007—Emission measurement accuracy.
(a) Minimum limit.
(1)
The minimum limit of an analyzer must be equal to or less than one-half of the average diluted concentration for an engine emitting the maximum amount of the applicable pollutant allowed by the applicable standard. For example, if with a given dilution and sampling system, an engine emitting NOX at the level of the standard (e.g., 0.20 g/bhp-hr NOX) would result in an average NOX concentration of 1.0 ppm in the diluted sample, then the minimum limit for the NOX analyzer must be less than or equal to 0.5 ppm.
(i)
The lowest NOX concentration in the calibration curve for which an accuracy of ±2 percent of point has been demonstrated as specified in paragraph (a)(3) of this section; or
(ii)
Any NOX concentration for which the test facility has demonstrated sufficient accuracy to the Administrator's satisfaction prior to the start of testing, such that it will allow a meaningful determination of compliance with respect to the applicable standard.
(3)
For determination of the analyzer's minimum limit, a NOX concentration that is less than or equal to one-half of the average NOX concentration determined in paragraph (a)(1) of this section shall be measured by the oxides of nitrogen analyzer following the analyzer's monthly periodic calibration. This measurement must be made to ensure the accuracy of the calibration curve to within ±2 percent of point accuracy of the appropriate least-squares fit, at less than or equal to one half of the average expected diluted NOX concentration determined in paragraph (a)(1) of this section.
(b) Measurement accuracy—Bag sampling.
Analyzers used for bag analysis must be operated such that the measured concentration falls between 15 and 100 percent of full scale, with the following exception: concentrations below 15 percent of full scale may be used if the minimum limit of the analyzer within the range meets the requirement of paragraph (a) of this section.
(c) Measurement accuracy—Continuous measurement.
(1)
Analyzers used for continuous analysis must be operated such that the measured concentration falls between 15 and 100 percent of full scale, with the following exceptions:
(i)
Concentrations below 15 percent of full scale may be used if the minimum limit of the analyzer within the range meets the requirement of paragraph (a) of this section.
(ii)
Analyzer response over 100% of full scale may be used if it can be shown that readings in this range are accurate.
(2)
If the analyzer response exceeds the level allowed by paragraph (c)(1)(ii) of this section, the test must be repeated using a higher range and both results must be reported. The Administrator may waive this requirement.
(d)
If a gas divider is used, the gas divider shall conform to the accuracy requirements specified in § 86.1314-84(g), and shall be used according to the procedures contained in paragraphs (a) and (b) of this section.