Central California Ozone Study (CCOS) - Desert Research Institute

CCOS Field Operations Plan Version 2: 5/31/00
the station ozone analyzer is taken off line. The station operator identifies the appropriate data
channel and disconnects the sample line from the sample manifold. After plugging the open port
of the sample manifold, the entire sample train of the ozone analyzer is connected to the
Environics Series 100 ozone generator output via a glass manifold. Care is taken to introduce
the ozone sample through as much of the normal sampling train (i.e., filters, and scrubbers) as
possible.
Ozone concentrations are determined by ultraviolet photometric methods and are
referenced to either CARB’s or AVES’s primary ozone standard. The zero air supplied by a zero
air generator is split into two streams. One of the air streams is directed through an ozone
generator that uses an ultraviolet lamp to convert diatomic air molecules into ozone. The second
air stream is directed into the ozone transfer standard sample bench and serves as the reference
air that determines the audit transfer standard baseline. This baseline value (which corresponds
to zero) is compared (by the transfer standard’s electronic systems) with the ozone bearing
sample stream. The difference between the reference and sample air streams is the audit
concentration as referenced to the AV primary ozone standard. The audit compares the readings
of the audit transfer standard determined concentrations with the corresponding station analyzer
DAS and chart recorder outputs. The audit transfer standard and the station ozone analyzer
sample the same sample outputs from a glass manifold connected to the ozone generator output.
Ten consecutive readings of the audit transfer standard and the station ozone analyzer DAS and
chart recorder outputs are taken at each of the concentration ranges (specified in the next subsection)
and averaged. The averaged audit transfer standard readings are corrected for
temperature and pressure and the correction factor from the certification with the AVES primary
standard. These corrected audit values and the corresponding station ozone analyzer values are
then compared by a least squares linear regression analysis and compared with the EPA
recommended criteria (Table 4.5-2).
The ozone analyzers are challenged with specific concentrations of span gas as follows:
Audit Points
Concentration Range (ppm)
1 0.000
2 .03 to .08
3 .15 to .20
4 .35 to .45
Continuous Analyzers. The continuous analyzers (including NO/NO x , NO/NO y , CO, and
CO 2 ) are all initially audited in a similar manner. The audits of the analyzers begin with the
station technician identifying the appropriate data channel and taking it off line so that ambient
data were no longer being collected. Next, the station technician disconnects the sample line of
the corresponding analyzer from the sample manifold. After plugging the open port of the
sampler manifold, the sample line or inlet filter is connected to the dilution system via a vented
glass manifold through which the audit span gas is introduced to allow the audit test atmosphere
to travel through as much of the normal sampling train (i.e., filters, scrubbers, etc.) as possible.
The analyzer is challenged with specific concentrations of span gas as follows:
Audit Point
Concentration Range
NO, CO, CO 2
Chapter 4: QUALITY ASSURANCE 4-20