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Model 400E Ozone Analyzer
Instruction Manual
8.5. Auditing Procedures
An audit is an independent assessment of the accuracy of data. Independence is
achieved by having the audit made by an operator other than the one conducting
the routine field measurements and by using audit standards and equipment
different from those routinely used in monitoring. The audit should be a true
assessment of the measurement process under normal operations without any
special preparation or adjustment of the system. Routine quality control checks
(such as zero and span checks) conducted by the operator are necessary for
obtaining and reporting good quality data, but they are not considered part of the
auditing procedure.
Three audits are recommended: two performance audits and a systems audit.
These audits are summarized in Table 8-2 at the end of this section. See
Appendix 15 of the Q.A. Handbook (Reference 11) for detailed procedures for a
systems audit and for a performance audit, respectively.
Proper implementation of an auditing program will serve a twofold purpose: (1) to
ensure the integrity of the data and (2) to assess the data for accuracy. The
technique for estimating the accuracy of the data is given in Section 2.0.8 of the QA
Manual (Reference 11).
8.5.1. Multipoint Calibration Audit
A performance audit consists of challenging the continuous analyzer with known
concentrations of O
between the known concentration and the analyzer response is obtained, and an
estimate of the analyzer's accuracy is determined.
Known concentrations of O
by the primary UV photometric procedure or may be obtained using a certified O
transfer standard. Procedures used to generate and assay O
same as those described in Section 8.1.3. If during a regular field audit, the
differences recorded for most analyzers are either negatively or positively biased, a
check of the calibrator used in routine calibrations of the analyzers may be
advisable.
The test atmosphere must pass through all filters, scrubbers, conditioners, and
other components used during normal ambient sampling and through as much of
the ambient air inlet system as practical. Be sure the manifold includes a vent to
assure that the M400E inlet is at atmospheric pressure.
P/N 04316 Rev: B
within the measurement range of the analyzer. The difference
3
must be generated by a stable O
3
EPA Protocol Calibration
source and assayed
3
concentrations are the
3
3
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