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T400 Ozone Analyzer Operator’s Manual EPA Protocol Calibration
217
data. Initially, the audit should be performed 1 day out of every 2 weeks of data. For
two 1-hour period within each day audited, make independent readings of the strip chart
record and continue through the actual transcription of the data on the SAROAD form.
The 2 hours selected during each day audited should be those for which either the trace
is most dynamic (in terms of spikes) or the average concentration is high.
The data processing audit is made by calculating the difference,
Equation 10-4
d = [O
3
]
R
- [O
3
]
A
Where
d = the difference between measured and audit values, ppm,
[O
3
]
R
= the recorded analyzer response, ppm, and
[O
3
]
A
= the data processing O
3
concentration, ppm.
If d exceeds 0.02 ppm, check all
of the remaining data in the 2-week period.
10.4.2. SYSTEM AUDIT
A system audit is an on-site inspection and review of the quality assurance activities
used for the total measurement system (sample collection, sample analysis, data
processing, etc.); it is a qualitative appraisal of system quality.
Conduct the system audit at the startup of a new monitoring system and periodically (as
appropriate) as significant changes in system operations occur.
The recommended audit schedule depends on the purpose for which the monitoring data
are being collected. For example, Appendix A, 40 CFR 58
8
requires that each analyzer
in State and Local Air Monitoring Networks (SLAMS) be audited at least once a year.
Each agency must audit 25% of the reference or equivalent analyzers each quarter. If an
agency operates less than four reference or equivalent analyzers, it must randomly select
analyzers for re-auditing so that one analyzer will be audited each calendar quarter and
so that each analyzer will be audited at least once a year.
Appendix B, 40 CFR 58
9
requires that each PSD (prevention of significant deterioration)
reference or equivalent analyzer be audited at least once a sampling quarter. Results of
these audits are used to estimate the accuracy of ambient air data.
10.4.3. ASSESSMENT OF MONITORING DATA FOR PRECISION AND
ACCURACY
A periodic check is used to assess the data for precision. A one-point precision check
must be carried out at least once every 2 weeks on each analyzer at an O
3
concentration
between 0.08 and 0.10 ppm. The analyzer must be operated in its normal sampling
mode, and the precision test gas must pass through all filters, scrubbers, conditioners,
and other components used during normal ambient sampling. Those standards used for
calibration or auditing may be used.
Estimates of single instrument accuracy for ambient air quality measurements from
continuous methods are calculated according to the procedure in Appendix 15 of the
Q.A. Handbook (Reference 11).
06870C DCN6332