Chimney was swept before the last gas fire was fitted, probably 2 years ago. It's a normal old style proper chimney. smoke pellet test was fine all drawn up fine with no spillage into the room.
I think there is too much ambiguity about the instructions, i.e. gas safe training/manufacturers instructions.
Especially with something as important as CO. How can you leave that to opinion? 'MOST' is like saying 'Tight' for a bolt torque setting!!!
We are not using the fire until it is sorted. We need to ring the manufacturers although they are shut over xmas!!