6.5 Mechanical and Electrical Systems
In the event of an explosion directed at a high-occupancy building, the primary objective is to protect people by preventing building collapse. Secondary goals are to limit injuries due to flying building debris and the direct effects of air blast entering the building (i.e., impact due to being thrown or lung collapse). Beyond these life-safety concerns, the objective is to facilitate building evacuation and rescue efforts through effective building design. This last objective is the focus of this section. Issues related specifically to chemical, biological, and radiological threats are discussed under a separate section with that heading.
The key concepts for providing secure and effective mechanical and electrical systems in buildings is the same as for the other building systems: separation, hardening, and redundancy. Keeping critical mechanical and electrical functions as far from high-threat areas as possible (e.g., lobbies, loading docks, mail rooms, garages, and retail spaces) increases their ability to survive an event. Separation is perhaps the most cost-effective option. Additionally, physical hardening or protection of these systems (including the conduits, pipes, and ducts associated with life-safety systems) provides increased likelihood that they will be able to survive the direct effects of the event if they are close enough to be affected. Finally, by providing redundant emergency systems that are adequately separated, there is a greater likelihood that emergency systems will remain operational post-event to assist rescuers in the evacuation of the building.
Architecturally, enhancements to mechanical and electrical systems will require additional space to accommodate additional equipment. fortunately, there are many incremental improvements that can be made that require only a small change to the design. Additional space can be provided for future enhancements as funds or the risk justify implementation.
Structurally, the walls and floor systems adjacent to the areas where critical equipment are located need to be protected by means of hardening. Other areas where hardening is recommended include primary egress routes, feeders for emergency power distribution, sprinkler systems mains and risers, fire alarm system trunk wiring, and ducts used for smoke-control systems.
From an operational security standpoint, it is important to restrict and control access to air-intake louvers, mechanical and electrical rooms, telecommunications spaces and rooftops by means of such measures as visitor screening, limited elevator stops, closed-circuit television (CCTV), detection, and card access-control systems.
Specific recommendations are given below for (1) emergency egress routes, (2) the emergency power system, (3) fuel storage, (4) transformers, (5) ventilation systems, (6) the fire control center, (7) emergency elevators, (8) the smoke and fire detection and alarm system, (9) the sprinkler/standpipe system, (10) smoke control system, and (11) the communication system. Air intakes are covered in Section 6.6.