Inner rooms - means of escape:

Inner rooms are rooms from which the means of escape require people to travel through another room (called the access room).  These are common in buildings and it is important that everyone in an inner room knows if a fire starts in the access room.

This warning of fire can be given by providing a clear window between the inner room and the access room that allows people in the inner room to see across the access room.  Alternatively the warning can be given if there is automatic smoke detection in the access room and the fire alarm sounder can be heard in the inner room.

Inner inner rooms, where the escape route is through two rooms, one after the other, are not generally acceptable.