Miele DA 186 Operating And Installation Instructions page 22

Installation
With air extraction:
If the on-site ventilation system does
not have a non-return flap, one of the
two non-return flaps supplied (for
C 150 mm or C 120 mm ducting) must
be fitted.
– If C 150 mm ducting is being used,
the non-return flap should be fitted
onto the exhaust connection.
With C 120 mm ducting, first fit the
reducing collar supplied onto the
exhaust connection and then fit the
appropriate non-return flap into the
reducing collar.
^ For extraction connection, secure a
flexible ducting or an extraction pipe
to the exhaust connection using a
hose clip.
^ Proceed with the exhaust connection.
(see "Connection for air extraction").
With recirculation mode:
^ Fit the charcoal filters (see "Cleaning
and Care").
22
^ Finally refit the grease filters.