Central California Ozone Study (CCOS) - Desert Research Institute

CCOS Field Operations Plan Version 2: 5/31/00
The converter efficiency for each audit point is:
[NO 2 converted]
⎯⎯⎯⎯⎯⎯⎯⎯⎯ x 100
[NO 2 input]
The converter efficiency is defined as the linear regression using the NO 2 source versus
the NO 2 converted x 100. The converter efficiency must be greater than or equal to 96% to pass
the audit. In addition to checking the converter efficiency for NO 2 , the converter is also checked
using NIST-traceable concentrations of n-propylnitrate. Concentrations of approximately 100
and 250 ppb are introduced into the analyzer, and the converter efficiency is calculated in the
same manner as for NO 2 . Finally, the analyzer’s scrubber is challenged with approximately 200
ppb of ammonia to document the analyzer’s response to common non-NO y compounds.
Ammonia concentrations are generated using NIST-traceable cylinders.
Carbon Analyzers. The continuous carbon analyzers are audited in much the same way as
other continuous gas analyzers, such as the NO/NO y analyzers (not including the GPT and
additional supplementary checks). Input concentrations of CO 2 are generated using an audit
dilution system and NIST-certified cylinders of CO 2 .
Nephelometers. The nephelometers are audited by performing a check of the instrument
zero and one upscale span point. The zero point is produced by inputting filtered zero air into
the nephelometer’s optical sampling chamber and noting the output readings after period of
approximately 5 minutes. The span point is produced in the same manner as the zero point but
with the introduction of the Suva refrigerant in place of the zero air. Audit criteria for the
nephelometers are similar to those for other continuous analyzers, as presented in Table 5-2.
Aethelometers. The Aethelometer sample flow rate is audited using an appropriate flow
standard. Responses should be within ±10% of audit values.
Additional Samplers and Analyzers. Specific audit procedures for specialized, research
instrumentation will be developed as SOPs are received. This includes instrumentation such as
automated VOC analyzers, HCHO dihydorlutinine derivative/fluorescent detection analyzers,
TDLAS analyzers, and hydroxyl carbonyl samplers.
4.5.7.2 Audits Conducted by ARB
The California Air Resources Board (ARB) will be conducting audits of the majority of NOx,
NOy, and ozone analyzers used for CCOS. While the auditing principles used by ARB are
essentially the same as those presented above, the ARB introduces their audit gases directly into
the sample probe using a mobile van equipped with the necessary calibration equipment that is
parked immediately adjacent to the site. This auditing method is briefly summarized below:
The Quality Assurance Section (QAS) conducts thru-the-probe audit by diluting known
quantities of National Institute of Standards and Technology (NIST) traceable gases with 25
liters of pure air to achieve ambient levels, then challenging the analyzers through the site’s inlet
Chapter 4: QUALITY ASSURANCE 4-22