I'm not sure what you it is you are calling a "coffered ceiling" but I suspect it's what I call a "pan ceiling". It's where the ceiling has a step in it and maybe a soffit type look to it. If that's the case I'd ask for the smoke alarm to be in the highest part of the ceiling. You have a similar situation when they have a cathedral ceiling and the area by the door has a common 7 foot 6 inch height. This would agree with some graphic I've seen in the NFPA 72 Handbook and in the manufacturers instructions. You know the ones that show the peak of the ceiling as a triangle with the base of not more than 6 feet. When you do the geometry and for an easy visual inspection, if the rough inspection shows the box within 3 feet of the peak you can bet it's within this imaginary triangle no matter what the pitch is.
[This message has been edited by George Little (edited 08-20-2005).]
