Hello. I'd like to get a Decorative Fuel Effect fire with a rating over 6.9 kw but I understand that the room will need additional ventilation. Can I use a second, separate, disused chimney breast in the same room for the vent or does it have to go directly outside? The breast currently has a couple of bricks missing so I hoped I could calculate the free air volume needed and install the right vent size. Also, the chimney is clapped with a C Cap for ventilation but I don't know the free air volume of that. Any advice? Thanks.