Where should that additional air supply be located?

Preferably as close as possible to the point where the air is needed:

• for a wood stove: near the stove;
• for an extractor hood: in or near the kitchen.

This means the required air does not first have to be drawn through the home from bedrooms or other rooms. The exact execution and capacity should be determined in the design, depending among other things on the stove type, its power rating, the chimney, the extractor hood and the airtightness of the home.