User Manual Bosch DWB96BC50A 90cm Serie 2 Canopy Rangehood

This can very a bit depending on the brand, but in general a cooker hood should be placed at least 65 centimeter above a gas hob and at least 50 centimeter above an electric or induction hob. This is to improve fire safety

Cooker Hoods with motor are meant for when the air is moved directly outside. A cooker hood without motor is meant for when there is a central ventilation system. Never connect a cooker hood with motor to a central ventilation system!