We did have one at the point where it exited the kitchen (pre-ducting, we ducted between the hood and the exit point) - about 5m of ducting away, but that was removed as the two fans would conflict each other, if one was off, and the other on, etc. They were on separate switches (at the time). The power is still available to there, so we could put it back in, but it woudl still be on a separate switch.
We did have one at the point where it exited the kitchen (pre-ducting, we ducted between the hood and the exit point) - about 5m of ducting away, but that was removed as the two fans would conflict each other, if one was off, and the other on, etc. They were on separate switches (at the time). The power is still available to there, so we could put it back in, but it woudl still be on a separate switch.