Turns out it was the emergency exit light fixture. So the device in the building to make us safer in case of a fire - caused the fire.
Boulder definitely has a good fire response - 4 fire trucks, 1 SUV, and 2 police cars. (They send that much because when you call in smoke and can't find the fire - it can be a bad situation with the fire inside the walls.)
That was our excitement for today. Back to work tomorrow.