Md. Code Regs. - Zero Alignment Audit

A. General Requirements.
(1) A zero alignment audit conducted in accordance with Regulation .08B of this chapter shall compare the monitor responses to the simulated zero check and the actual clear path condition. Primary and alternate methods for performing the zero alignment audit are described in ┬žA(2) and (3) of this regulation.
(2) Primary Zero Alignment Method.
(a) The primary zero alignment method shall be performed under clear path conditions. This is accomplished for the installed transmissometer where the process is not operating and the monitor pathlength is free of particulate matter or the monitor may be removed from its installation and set up under clear path conditions.
(b) No adjustment to the monitor should be made other than the establishment of the proper monitor pathlength and correct optical alignment of the transmissometer components. For some monitors it may also be necessary to disable the zero compensation mechanism or to record the amount of correction applied to the simulated zero condition.
(c) The monitor response to the clear path condition and to the simulated zero condition shall be recorded as percent opacity.
(d) The response difference in percent opacity to the clear path and simulated zero conditions shall be recorded as the zero alignment error. The simulated zero device shall then be adjusted to provide the same response as a clear path condition.
(e) The monitor shall then be restored to its operating mode at the facility.
(3) Alternate Zero Alignment Method.
(a) An external, removable zero-jig may be used to facilitate periodic checks of the simulated zero condition as an alternate zero alignment audit method if:
(i) The zero-jig setting is established for the specific monitor by comparison of the monitor responses to the zero-jig and to clear path condition; and
(ii) The zero-jig is capable of producing a consistent zero response when it is repeatedly installed on the monitor.
(b) The zero-jig shall be protected when not in use to ensure that the setting equivalent to zero opacity does not change.
(c) Source owners who use a zero-jig shall perform a primary zero alignment audit and check of the zero-jig setting at least once every 3 years.
B. Criteria for a Successful Audit.
(1) Performance Audit. Performance of the COM shall be considered acceptable if it meets the following criteria:
(a) Stack Exit Correlation Error: < 2 percent opacity;
(b) Fault Indicators: Inactive/no error messages present;
(c) Zero and Upscale Responses: < 2 percent opacity;
(d) Zero compensation: < 4 percent opacity;
(e) Optical Alignment: misalignment error < 2 percent opacity;
(f) Optical Surface Dust Accumulation: < 4 percent opacity; and
(g) Calibration Error: < 3 percent opacity.
(2) Zero Alignment.
(a) Calculations for a zero alignment audit shall be in accordance with the EPA document incorporated by reference in Regulation .03B(2) of this chapter.
(b) The zero alignment is acceptable if the error of the simulated zero check is less than 2 percent opacity before adjustment.
(c) The simulated zero check should be adjusted to provide the correct response each time the zero alignment audit is performed.
(3) Out-of-Control Periods. The beginning of the out-of-control period is the time corresponding to the completion of the performance audit indicating unacceptable performance. The end of the out-of-control period is the time corresponding to the completion of the subsequent successful audit.


Md. Code Regs.
Regulations .11 under new chapter, Quality Assurance Requirements for Continuous Opacity Monitors (COMs) adopted effective June 13, 2011 (38:12 Md. R. 708)

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