Md. Code Regs. 26.11.31.09

Current through Register Vol. 51, No. 24, December 2, 2024

Section 26.11.31.09 - Performance Audit

A. Each performance audit shall include a series of checks of individual monitoring system components and factors affecting the accuracy of the monitoring data.

B. Calculations for COM data shall be in accordance with monitor specific calculations in the EPA document Performance Audit Procedures for Opacity Monitors, which is incorporated by reference in Regulation .03B(2) of this chapter. Examples of detailed audit procedures are also found in that referenced document.

C. A performance audit shall include checks for each procedure in an approved QC program, including, at a minimum, the following checks:

(1) Stack Exit Correlation Error.

(a) The value of the pathlength correction factor used by the monitor is measured according to procedures specified by the manufacturer.

(b) The correct value of the pathlength correction factor is computed from the monitor pathlength and stack exit diameter.

(c) The stack exit correlation error is determined as the ratio of the measured value to the correct value and is expressed as a percent.

(2) Fault Indicators. Fault lamp indicators, data acquisition system error messages, and other system self-diagnostic indicators are examined to determine if the COM is operating within preset limits.

(3) Zero and Upscale Responses.

(a) The COM responses to the simulated zero condition (or low-level) and upscale calibration value are determined from the permanent data recording device according to the routine CD check procedure.

(b) The zero and upscale response errors are determined from the permanent data recording device to the routine CD check procedure.

(c) The zero upscale response errors are determined as the difference between the corrected values and the observed response for the zero and upscale calibration check.

(4) Zero Compensation. The value of the zero compensation applied at the time of the audit is determined as equivalent percent opacity. The value is corrected to stack exit conditions, according to the procedures specified by the manufacturer, where the applicable monitor includes an automatic correction to compensate for drift in the monitor's response to the simulated zero opacity condition or dust accumulation on the optical surfaces of the transceiver.

(5) Optical Alignment. The status of the optical alignment of the transmissometer components shall be determined using an alignment sight that indicates that the monitor is misaligned when a measurement error of 2 percent opacity or greater is caused by misalignment, in accordance with Performance Specification 1 incorporated by reference under Regulation .03B(1) of this chapter.

(6) Optical Surface Dust Accumulation.

(a) An estimate of the amount of dust (or other particulate matter) deposited on the exposed optical surfaces of the transmissometer is obtained by recording the apparent effluent opacity before and after cleaning of each of the exposed optical surfaces.

(b) The total optical surface dust accumulation is the sum of the apparent reduction in opacity for all of the optical surfaces that are cleaned.

(7) Calibration Error. The COM responses are compared using one of the following methods to the known values of three reference neutral density filters corrected to stack exit conditions:

(a) The preferred method requires the installation of an audit device, adjusted to provide the same zero response as the monitor's simulated zero check, that simulates the clear path condition and allows insertion of the filters into the light path; or

(b) In those cases where an audit device is not available, an alternate method may be used by conducting an incremental calibration (that is, superimposing the audit filters and effluent opacity) and comparing the monitor response to the expected value calculated from the filter and effluent opacity values. This method is sensitive to fluctuations in the effluent opacity during the test.

Md. Code Regs. 26.11.31.09

Regulations .09 under new chapter, Quality Assurance Requirements for Continuous Opacity Monitors (COMs) adopted effective June 13, 2011 (38:12 Md. R. 708)