The fact, that a wooden stair burn quickly is just a part of the bad safety with a fire. A wooden stair transports the fire easily to the other levels of the building. That gives very dangerous situations. A wooden stair in a dwelling house need to be fire free for 20 minutes if there is a fire in a dwelling house. Stairs are needed for convenient and safe going from one level to another one. They are also necessary for evacuating people in emergency cases. A wooden staircase consists of the bottom and top stair landings, the two strings (or string boards) and a number of successive steps.