Miele S500 Operating Instructions Manual page 34

Some models are equipped with an
exhaust filter change indicator (Reset
button 7) which is designed to alert
when to change the "ACTIVE air clean"
or "ACTIVE HEPA" filter.
The indicator lights up after about 50
hours of operation, which is equivalent
to about a year of average use. The
vacuum cleaner can still be used with
the exhaust filter indicator lit. However,
the suction power will be reduced as
will the effectiveness of the filter if it is
not replaced.
Note: If a "SUPER air clean" filter is
being used, the filter change indicator
can be disregarded but should be
reset. The indicator goes out when the
Reset button is pressed.
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