Principle of Means of Escape:
The means of escape with which a building is provided are simply the ways out of the building that can be safely used in the event of a fire. It is not essential that all means of escape (i.e. exit routes) remain available for use in the event of a fire provided that there are sufficient exit routes to allow everyone to escape safely.
In other words, it is accepted that an exit route might be lost because of the location of a fire and this has to be considered when designing or assessing means of escape so that it can be assured that the exits that do remain available during the fire will have sufficient capacity and will be suitably accessible for the maximum number of people who are expected to have to use them.
Wherever the fire is located, all people in the building should be able to escape safely. Safe means of escape do not include: