Revision A
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6. After the unit has finished scanning for the 0% reference, switch the selector valve to
<DOWNSTREAM>. The % LEAKAGE display indicates the concentration as
compared to the upstream value.
3.8 TESTING WITH THE 2H
After the 100% and 0% baselines have been established, the unit is ready for testing operations.
During testing operations, readings may be taken from either the Front Panel Display or the
Scanning Probe, lessening operator distraction.
Testing is performed as follows:
1. Turn the selector valve to DOWNSTREAM to permit sampling through the Scanning
Probe.
2. Pass the end of the probe over the filter being tested at the rate required by the standard
or recommended practice being employed.
3. Read and record the data as it is displayed on either the pistol grip of the probe or the
Front Panel Display. Once the 100% baseline has been properly defined, the display
readings are given directly in % leakage.
Note: Most current standards and recommended practices require leaks of greater than 0.01%
to be identified and repaired.
3.9 VERIFYING THE UPSREAM CONCENTRATION DURING TEST
Turn the Selector Valve to the UPSTREAM position. The % LEAKAGE display shows
the concentration of the upstream challenge aerosol in percent of upstream calibration.
The photometer is comparing the real-time concentration of the upstream challenge to the
concentration of this same source when it was initially used to establish the 100% baseline.
In other words, it is comparing the current concentration level to the starting level.
If the reading seems reasonable, normal testing may be resumed by turning the Selector
Valve back to the DOWNSTREAM position.
If the concentration of the challenge aerosol has changed significantly, the upstream source
should be examined for the cause. Once the situation has been corrected, the upstream
challenge aerosol should be restarted, stabilized, and then used to re-establish the 100%
baseline as described previously.
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