Apex Instruments and the EPA recommends that the user perform post-test audits following a field test
series using the procedures outlined in EPA Method 5, Section 10.3.2 Calibration After Use. This
procedure closely mirrors the pre-test calibration, except only three runs need to be made that are at
or near the sample rate metered and at or higher than the vacuum observed during the test.
The average of the post-test audit factors, Y, is not allowed to deviate more than 5% from the pre-test
calibration factor Y. If this deviation is greater than 5%, a post-test calibration factor needs to be
i
redetermined using the Pre-Test Calibration procedure. This new post-test calibration factor is then
compared to the post-test audit factor and whichever is smaller is accepted as the DGM calibration
factor.
Conduct a post-test audit using the audit procedure outlined in Section 3.4 Post-Field Test Operations
on page 25 of this manual. If the Q obtained before and after the test differ by more than 5%,
m(std)
void the test run; if not, calculate the volume of the gas measured with the critical orifice.
If recalibration indicates that the metering system is unacceptable for use, void the test results or use
approved methods by the administrator to determine an acceptable value for the collected sample.
Audit against mercury-in-glass thermometers. An alternative thermometer may be used if the
thermometer is, at a minimum, equivalent in terms of performance or suitably effective for the specific
temperature measurement application (EPA Method 5, Section 10.5).
The user can also audit the temperature sensors following the procedure outlined in Section 4.1.2
Initial end user audits on page 45 of this manual.
4.2 Post-Test Calibrations
4.2.1 Dry gas meter
4.2.2 Temperature sensors
XD-502 Digital Console
Apex Instruments, Inc.
46
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