Most Smeg hoods offer the choice of ducting or re-circulating, so you can choose your preferred method.
Ducting out extracts cooking fumes and expels them outside, using a vent kit (available as an optional accessory) The diameter of the ducting hose should match the vent outlet of the hood.
SP215 - Simple vent kit for hoods with a 120mm diameter vent outlet
SP217 - Comprehensive vent kit for hoods with a 120mm diameter vent outlet
Re-circulating extracts the cooking fumes and passes them through active charcoal filters (available as an optional accessory), recirculating the cleaned air back into the room. To find out which charcoal filter your hood needs, check the accessory tab on the hoods specification.