Bosch DWB093553 Mode D'emploi Et Notice De Montage page 24

Operating modes
The extractor hood can be used in exhaust
air and circulating air mode.
Exhaust-air mode
The air which is drawn in is cleaned by the
grease filters and conveyed to the exterior by a
pipe system.
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Circulating-air mode
The air which is drawn in is cleaned by the
grease filters and an activated carbon filter
and conveyed back into the kitchen.
An activated carbon filter must be installed to
bind odours in circulating-air mode (see
"Removing and installing the grease filters").
The complete installation set as well as the
replacement filters are available from specialist
outlets, customer service or the Online Shop.
The accessory number can be found at the
end of the operating instructions.