Gary Hicks outlines some prime considerations when planning safe evacuations from tall buildings in events including terror attacks
OVER THE last decade or two, the attacks on the World Trade Center in New York have been well documented, along with incidents on tall buildings throughout the world before and after those tragic events. During that time, many design considerations and processes have been implemented where possible to reduce the chances of these events happening in the future.
It is beyond doubt that design, engineering, materials and systems are all built into international codes to ensure that buildings are constructed to the highest levels of safety.
In addition, building owners, management, occupiers and in some cases, local authority services, are responsible for ensuring that the correct procedures are in place should such an incident occur. However, while these certainly make a difference, have the actual operational procedures been addressed and are these the real issues involved in protecting vertical cities?
Explosive blast and chemical, biological, radiation (CBR) concerns from terrorist attacks highlight the need for mitigation measures that may be applied to building elements, including architectural, structural and building envelope systems.
When the desired level of protection cannot be achieved through site design (recognising that many site design considerations to enhance building protection may not be applicable to buildings in urban settings), additional building design measures, such as hardening of the building envelope, must be looked at.
Historically, the majority of fatalities that occur in terrorist attacks directed against buildings are the result of building collapse. This was true for the Oklahoma City bombing in 1995, when 87% of the building occupants who were killed were in the collapsed portion of the Murrah Federal Building.
When deciding on mitigation measures for explosive blast threats, the primary strategy is to keep explosive devices as far away from the building as possible by maximising stand-off distance. This is usually the easiest and least costly way to achieve a desired level of protection. In cases where sufficient stand-off distance is not available to protect the building, hardening of the building’s structural systems may be required, as well as design to prevent progressive collapse. In addition, designers should try to minimise hazardous flying debris during an explosive event, because a large number of injuries can result from flying glass fragments and debris from walls, ceilings and non-structural features.
The hardening of the building envelope should be balanced, so that the columns, walls and windows have approximately equal response for damage and injury/casualty for the design basis threat weapon at the available stand-off distance. Window design is the element that is usually the most diverse in conventional construction. Good blast engineering is a multi-disciplinary effort that requires the concerted efforts of the architect, structural engineer, mechanical engineer and the other design team members to achieve a balanced building envelope.
When considering mitigation measures for CBR hazards, the heating, ventilation and air conditioning (HVAC) systems are of concern. A building can provide protection against CBR agents released outdoors if the flow of fresh air is filtered or interrupted; however, HVAC systems can also become an entry point and distribution system for hazardous contaminants.
If installed, HVAC air filtration and air-cleaning systems can reduce the effects of a CBR agent by removing the contaminants from the air within a building. There are a variety of ways to protect building occupants from airborne hazards. These protective measures can be as simple as defining a protective action plan or as complex as strict design measures practical only for new construction. Another major concern is contamination of any other liquid systems.
Evacuation and rescue
Building design should be optimised to facilitate emergency evacuation, rescue and recovery efforts through effective placement, structural design, and redundancy of emergency exits and critical mechanical/electrical systems. Through effective structural design, the overall damage levels may be reduced to make it easier for people to get out safely and allow emergency responders to enter safely.
As with crime prevention through environmental design (CPTED), some of the leadership in energy and environmental design (LEED) concepts complement security concerns and others conflict with physical security principles.
The LEED Green Building Rating System represents the US Green Building Council’s (USGBC’s) effort to provide a national standard for what constitutes a ‘green building’. Through its use as a design guideline and third-party certification tool, it aims to improve occupant wellbeing, environmental performance and economic returnsof buildings using established and innovative practices, standards and technologies.
This voluntary building assessment tool is most applicable to commercial, institution and high rise residential construction. Owners, architects and engineers must work together to strike a balance between building design objectives.
LEED looks at six basic categories: Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, Indoor Environmental Quality, and Innovation and Design Process. Within each category, points are awarded for achieving specific goals. A total of 69 points is possible. A score of 26-32 points achieves basic certification; 33-38 achieves Silver; 39-51 achieves Gold; and 52-69 points achieve Platinum certification. The LEED rating is awarded after the project has been documented by the USGBC.
Another goal in this effort is to encourage more sustainable construction practices – LEED encourages manufacturers to provide materials that:
· contain high recycled content and sustainable use raw materials
· are manufactured close to the construction site
· have low volatile organic compound emissions
· are designed to minimise energy consumption and packaging
Tall buildings are constructed with impressive systems that are protected under many codes and passed fit for occupancy under strict guidelines. To function during and after an incident, these amazing vertical structures require procedures that underpin all the safety aspects incorporated into their design and that are tested on a regular basis. These procedures, strategies and a level of cooperation between many organisations help maintain the life safety of their occupants 24/7.
To fully understand the heartbeat of a vertical superstructure, it is important to identify the occupancy of a tall building. Typically, a high rise building will include commercial floors that could comprise a mall, hotel and residential units, and will also contain plant rooms. All stakeholders of that high rise building should be involved in the process of writing, operating, testing and fine tuning the procedures that could be crucial to life safety in the event of an incident.
An understanding of emergency services response times is essential during the development of these procedures, along with occupancy times of the building – as its use will determine how an emergency/Incident response team is organised.
A commercial unit may be manned for 12 hours, yet a hotel should be manned round the clock. The former property would be at its maximum occupancy level during the working day, whereas in the case of the latter this would be during the silent hours. From an organisational perspective, we can start to understand how difficult it can be to:
· communicate between organisations within a building
· set up procedures to suit that building
· train the emergency/incident response teams
· test and exercise the emergency/incident response teams
· provide cover for the emergency/incident response teams
· finance the ongoing training of the emergency/incident response teams
Communication between the building owners, management and the occupiers to build robust procedures, test and exercise these procedures could be the most important factor in ensuring that life safety is maintained in a tall building.
Terrorists are driven individuals or team members who could be planning an attack on a tall building we might live in or visit. How has the individual evolved? What do they look like? How will our building be attacked?
The everyday terrorist could be a member of staff, sub-contracted company staff member, visitor, delivery driver, client, member of the public or child. Within a building, the more vulnerable departments and systems are HVAC; mechanical, electrical, and plumbing (MEP); catering; human resources; housekeeping; and security services.
Recruitment should be looked at as a first response to an immediate threat, and in particular those involved in the operational management of safety in superstructures already in the built environment and new vertical cities being developed around the world.
Emergency response teams and their management need to be specially trained to deal with an incident until the emergency services are on scene ready to take control. The emergency services should be supported throughout the incident and the asset protected where possible throughout and after the incident.
Here’s a checklist for your consideration – which of these do you have or need to add?
· emergency evacuation plan
· business continuity plan
· operating procedures
· trained incident response team 24/7
· regular exercises
· communication with the emergency services
· employee family response plan
· media response plan
· evacuation equipment
· maintenance strategies for key systems
· recruitment plan
From an operational standpoint, the building’s decision makers need to buy into business continuity planning. If they do not think it important to allocate time and resources to ensure that sufficient training and exercises have been planned to provide the correct response during an incident, then there is a strong possibility that loss of life will occur, the asset and brand will be damaged, and severe financial losses will ensue.
Gary Hicks is an emergency management consultant at Evac+Chair International