Combined smoke management measures for common access areas of residential high-rise buildings
Physical barriers (smoke containment) may be combined with one of more of the other smoke management measures identified above. Care must then be taken to ensure that the different schemes firstly work individually, and secondly do not compromise one another. This last remark applies especially where pressure differentials are used for some of the common access areas.
While model-scale and full-scale experiments (in addition to tests on real buildings) on high-rise smoke management have been conducted worldwide, there remain unresolved issues in respect to the successful operation of the different approaches. While stairwell pressurisation and natural ventilation are to an extent now understood, the issue of what measures to then apply to corridors, lobbies, vestibules and the compartment/space of fire origin is not clear. Some form of smoke extraction or dilution in the corridors, and possibly vestibules if present, would seem beneficial not only for conditions inside these spaces, but also for the successful operation of the smoke management scheme for the stairwell. Pressurisation of the corridor and/or vestibule may also be of benefit, but the design of these systems is viewed by many as being complicated, and hence perhaps prone to failure.
It is clear that building stack and wind effects can be very important. While these are not easily quantified in a physical-scale model, they can be addressed more readily by numerical modelling.
While the influence of sprinklers acting on the fire source can be expected to generally have a beneficial effect, the interaction with other smoke management components requires careful consideration. Benefits achieved by limiting the fire heat release rate, and hence lowering temperatures and expansion/buoyancy forces, may be offset in part at least by higher volumes of cooler smoke, possible containing greater concentrations of hazardous gases such as carbon monoxide.
An important consideration on the overall smoke management design is the evacuation procedure. While there has been a tendency in the UK to adopt the procedure whereby occupants of non-fire dwellings do not evacuate unless told to do so (e.g. by the Fire Service), in many other parts of the world the preference has been for whole building evacuation. This can have an important bearing on the allowable conditions inside the common corridors and lobbies in particular. However, the whole building evacuation policy has been questioned now in North America [e.g. Proulx, 2001] and the alternative, non-evacuation procedure has been suggested.
© Building Research Establishment Ltd 2005