TSI Instruments ALNOR AIRGARD 200 Owner's Manual page 13

WARNING
This method is only used as a temporary condition to set the low
flow point. Make sure air flow is restored to proper level after
calibration.
Step 5: Using a properly calibrated thermoanemometer,
determine the velocity through the face of the hood by taking a
detailed velocity traverse. Divide the face area of the hood into
equal partitions. One reading per square foot of face area is
recommended for an accurate traverse. Compute the average
velocity for this area. For this example, assume that the traverse
resulted in an average velocity of 70 fpm.
Step 6: If the red indicator is illuminated, slowly turn the
adjustment screw counterclockwise until the green indicator
illuminates. If the green indicator is illuminated, slowly turn the
adjustment screw clockwise until the red indicator illuminates;
now slowly turn the adjustment screw counterclockwise until the
green indicator illuminates. It is important that these adjustments
be done in small increments, at intervals of about ten seconds
each, to allow for the delayed reaction of the alarm.
Step 7: Restore fume hood air flow to a normal level.
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