Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 145)

Model 9110EH Instruction Manual EPA Protocol Calibration
8. EPA PROTOCOL CALIBRATION
To ensure high quality, accurate measurements at all times, the M9110EH analyzer must be
calibrated prior to use. A quality assurance program centered on this aspect and including
attention to the built-in warning features of the analyzer, periodic inspection, regular
zero/span checks, regular evaluation of test parameters for predictive diagnostics and data
analysis and routine maintenance of the instrument are paramount to achieving this goal.
The US EPA strongly recommends to obtain a copy of the Quality Assurance Handbook for
Air Pollution Measurement Systems, Volume II, Part I (abbreviated Q.A. Handbook
Volume II). A new revision of this handbook is in progress 8 . A draft version of Section 2.3
can be downloaded online 8 and should be consulted as the latest reference about NO
2
measurements.
Special attention should be paid to Section 2.3 of the handbook 8
which covers the
measurement of NO
2
. Specific regulations regarding the use and operation of ambient NO
x
analyzers can be found in Reference 1 at the end of this chapter.
If the M9110EH is used for EPA compliance monitoring, it must be calibrated in accordance
with the instructions in this section.
8.1. Calibration of Equipment
In general, calibration is the process of adjusting the gain and offset of the M9110EH against a
standard with certified, traceable concentration. The reliability of data derived from the
analyzer depends primarily upon its state of calibration. In this section the term dynamic
calibration is used to express a multipoint calibration against known standards. It involves
introducing gas samples of known concentration into the instrument in order to adjust the
instrument to a predetermined sensitivity and to produce a calibration relationship. This
relationship is derived from the instrumental response to successive samples of different,
known concentrations. As a minimum, three reference points and a zero point are recom-
mended to define this relationship. The true values of the calibration gas must be traceable
to NIST-SRM (Section 2.0.7, Q.A. Handbook).
All monitoring systems are subject to some drift and variation in internal parameters and
cannot be expected to maintain accurate calibration over long periods of time. Therefore, it
is necessary to dynamically check the calibration relationship on a predetermined schedule.
Zero and span checks must be used to document that the data remain within control limits.
These checks are also used in data reduction and validation. The internal data acquisition
system of the M9110EH allows to store all calibration checks (as well as full calibrations) over
long periods of time for documentation. Table 8-1 summarizes the initial quality assurance
activities for calibrating equipment. Table 8-2 is a matrix for the actual, dynamic calibration
procedure.
Calibrations should be carried out at the field monitoring site. The analyzer should be in
operation for at least several hours (preferably overnight) before calibration so that it is
fully warmed up and its operation has stabilized. During the calibration, the M9110EH should
be in the CAL mode, and therefore sample the test atmosphere through all components
used during normal ambient sampling and through as much of the ambient air inlet system
as is practicable. If the instrument will be used on more than one range, it should be
calibrated separately on each applicable range, see Section 6.6. Calibration documentation
should be maintained with each analyzer and also in a central backup file.
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