It is a requirement of the New Zealand Building Code that spaces in household units, including apartments, that contain cooktops must have mechanical extract that discharges outside. This is typically achieved through a rangehood which are often rated to a maximum “length of duct”.
Some entry level rangehoods may only be rated for as little as 3m by the supplier or even rated to only discharge immediately through the wall they are installed on. This can pose a problem. In modern day apartments it is not unusual for the kitchen to be located 5m or more from the point of discharge!
Duct fittings like a 90° bend may be equivalent to 2m or more of straight duct in the suppliers documentation. A rangehood rated for a maximum “duct length” of 5m could be reduced to only 3m with just one bend! Careful consideration of the duct route and rangehood requirements must be taken when locating the kitchen and oven.
When choosing a kitchen rangehood it is important to consult with the supplier and the project mechanical engineer for proper pressure drop calculations to confirm whether the rangehood will meet the required performance.