We can see the amount of soot accumulated on what is left of this ceiling. This could prove hazardous to anyone who is attempting to breathe in the area and or the roof could collapse. 

Fires burn hot and can rage for quite a long time depending on a few variables. How much oxygen they can get to continually fuel the flame, as well as how easy they are to fight from a firefighters perspective. 

In this picture we can see the soot damage on the wall of a fire that began in the basement of a home. The fire went up the back staircases of the home to the second floor. 

This picture is of a recent fire in Reading that the SERVPRO of Pottstown/Souderton team just boarded up.  The house is condemned and no occupancy is allowed at this time.

The remnants of a fire are always water and soot. Depending on the severity and the type of soot, items can be salvaged. In this pic, we see the door to a home that is covered in soot. 

After a fire, the most noticeable thing left over is the soot.  Generally, most things must be removed and destroyed but it depends on the severity of the fire as to whether or not anything is salvageable.