I have been in my new position for a little over a month when last week my Supervisor called me at my office telling me to “drop everything, there has been a fire at the Springfield office!” I told him that this wasn't in my district, and he then replied “Go!” During the long travel he updated me via cell with the details,and it appeared that the heater in the facility had caught fire and while smoke filled the building, the damage was confined to the heater unit. This was according to the building mechanics who were the first responders. They had disconnected the power to the unit, and diagnosed a failed indoor fan motor. This was the source of the smoke in the building was their analysis. With that much being known, and the mechanics now cleared out, my boss required that I still go and put a final cap on the report. Scary! When I looked over the partially disassembled unit, I found no sign of damage; soot, melted or toasted stuff...nothing to show a fire had occurred. Hmmm. Since the building still had this acrid burnt smell, and several individuals had reported seeing white smoke flowing from the air registers, I wasn't quite satisfied with just exactly what was known to this point. (fast forward) The fan control relay had burnt out, and that took the indoor fan out of the system. The nasty part of all of this was that the sensor (hi temp limit switch) failed and allowed the heater to fire up with no airflow through the heat exchanger. This is a bad thing! The smoke was from the dust and particulate matter inherent in all duct work that was roasting to the point of just short of combustion. I pulled the heater control board for replacement, as much like every piece of equipment out there today, if a component goes bad the whole board gets tossed. This is why I entertained myself modeling the board. Difficult to say where or when we find our inspiration to model, no?