Air bricks

[bodgeitandscarper]

My sister has just asked me to put air vents at the top of the chimney breast in each room.

Isnt the vent usually at the bottom of the chimney breast, does it matter if it's near the ceiling?

I under stand that the chimney breast will hold the chimney from the room underneath , how do I determine that I knock into the correct chimney for the room? Does that make sense!