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EPA Protocol Calibration T400 Ozone Analyzer Operator’s Manual
216
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 10.4.2 at the end of this section. See Appendix 15 of the Q.A.
Handbook
(Referen
ce 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).
MULTIPOINT CALIBRATION AUDIT
A performance audit consists of challenging the continuous analyzer with known
concentrations of O
3
within the measurement range of the analyzer. The difference
between the known concentration and the analyzer response is obtained, and an estimate
of the analyzer's accuracy is determined.
Known concentrations of O
3
must be generated by a stable O
3
source and assayed by the
primary UV photometric procedure or may be obtained using a certified O
3
transfer
standard. Procedures used to generate and assay O
3
concentrations are the same as those
described in Section 10.1.3. If during a regular field audit, the differences recorded for
mo
st 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 T400
inlet is at atmospheric pressure.
Audit Procedure:
1. Turn on the zero-air flow in the audit device.
2. After stabilization, record the analyzer zero.
3. Generate an up-scale audit point.
4. After stabilization, record the O
3
analyzer response.
5. Assay the audit concentration using an audit UV photometer or certified transfer
standard.
6. Repeat steps 4 and 5 for the two remaining up-scale audit points. If analyzer is
operated on 0-1.0 ppm range, four up-scale audit points must be used.
Results:
Results of the audit will be used to estimate the accuracy of the ambient air quality data.
Calculation of accuracy is described in Appendix 15 of the Q.A. Handbook (Reference
11).
10.4.1. DATA PROCESSING AUDIT
Data processing audit involves reading a strip chart record, calculating an average, and
transcribing or recording the results on the SAROAD form. The data processing audit
should be performed by an individual other than the one who originally reduced the
06870C DCN6332