Miele S5981 - Manual (Page 26)

When to change the Active
HEPA exhaust filter
Always change the Active HEPA filter
when the filter change indicator (Reset
button) lights. It is designed to light
after approximately 50 hours of
operation which is about a year of
average use. You can continue to
vacuum. However, the suction power
will be reduced as will the effectiveness
of the filter if it is not replaced.
You can replace the "Active HEPA" filter
supplied with the cleaner with an "Air
Clean" or an "Active Air Clean" filter (see
"Exchanging exhaust filters").
Maintenance and care
26