BigJohn - The discoloration on your bricks indicates that you are getting a small amount of down drafting. This is normally caused by negative pressure in the house. Next time, try cracking a window - this should equalize the pressure between inside & out.
Bilbo - Do you have a fan on that unit? On gas units, if the fan is off, the heat rolls straight up the front and warms anything directly above it. We constantly get customers calling in a panic because the "wall" above their fireplace is so hot they can't touch it. (As long as the unit was installed to code, this heat doesn't even approach the flash point of wood, drywall, etc.)
If the fan is running, the heat is forced out into the room, and the wall above stays quite cool.
