I heard fire escape ladders or rope ladders cannot be used to get out of your building window if the room directly below is on fire. I would imagine because the ladder then would catch fire? If that's true, what are other methods to safely get out of your window, if the window escape was your only option?
This is why every livable room is required to have at least two ways to exit room. If all paths are blocked, you then have to wait for the fire department to come with the ladder truck. Any other means will put you in greater dander.
Also it is not the ladder catching on fire that is the concern, but climbing through heat/fire/smoke that will make it impossible.