Mr. Dennis Keeley:

Security is a factor. However, from a fire safety perspective it is about the ability for an enclosed space to be protected, versus an open space which can be impacted by fire from several different floors. If the stairwell is open, the question is whether it can be impacted by fire impinging on that stairwell from one of the windows or from another door, therefore impacting the possibility of evacuation or access by firefighters. It is about how well escape routes and access can be protected and if that level of protection is equal, whether internal or external. It is very much a design constraint depending on the building itself. There are a number of factors but it is predominantly about the safety and protection of the exit route. If it is an exit route to afford evacuation for residents or access to firefighters, it has to be protected. The challenge is different depending on whether it is external or internal.