H-25C Instruction Manual
Instruction 3015-0216
44
5.2 Replacing the Activated Charcoal Filter
The measured gas going to the sensor is split into two a by a manifold, one stream being introduced with no
treatment, the other being introduced after being passed through the activated charcoal filter to convert it to clean,
pure air. If the activated charcoal filter is unable to purify the measured gas, the result will be the same as if extra
untreated measured gas were flowing into the sensor, giving a too-high indication for the leak rate.
Since allowing extra untreated gas to flow into the sensor will shorten the sensor life, in addition to causing
measurement errors, you must replace the activated charcoal filter before it loses its effectiveness at conversion.
In general, if you are using the H-25C seven hours a day, an activated charcoal filter can be used for 30 to 60
days. We recommend that you schedule periodic replacements using these numbers as guidelines. If the
measurement check described in Subsection 4.2.6 reveals error in the measurement, you should replace the filter
promptly.
Note : The service life of the activated carbon filter may be greatly reduced if a large amount of freon gas is
contained in the atmosphere.
The replacement procedure is as follows:
(1) Disconnect the tube from the tube joint attached to the activated-charcoal filter ( case cap ).
(2) Remove the activated-charcoal filter (filter case) from its mounting seat. (It is screwed into the seat, and must
be turned counterclockwise to remove it.)
(3) Turn the case cover counterclockwise to remove the cover.
(4) Remove the used filter pack from the case.
(5) Take out a new filter pack from its bag.
