High-rise apartment fires – evacuate or not?

by FM Media
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Fire

The safest option in the event of fire in a high-rise residential building may be to not evacuate at all, says DAVID BARBER from Arup Fire, who is carrying out a major study assessing evacuation options.

The Australian Bureau of Statistics indicates that high-rise housing in Australia is currently increasing at a faster rate than the total population. It is expected to continue increasing as the growth of urban living and resistance to urban sprawl requires city planners to utilise building height to house a growing population. Throughout the world high-rise residential buildings have fairly common construction methods, floor layouts and occupant characteristics.
A study into the effectiveness of high-rise residential building evacuation is currently underway to ascertain the most appropriate method of providing protection for occupants in a fire emergency.
The Building Code of Australia states that all new buildings over 25 metres in height are required to have an Emergency Warning and Intercom System (EWIS) in accordance with Australian Standard 1670.4 (among other fire safety features). This standard recommends that apartment owners or an Owners Corporation will implement a cohesive phased evacuation plan to the Australian Standard 3745.
Following the methodology outlined within AS 3745, the successful use of an EWIS requires a team of volunteer floor warden, who need to be well-trained, and a chief warden to guide the phased evacuation. Regular training and drills by building occupants are also required. All wardens need to be available to implement the phased evacuation instructions on the first alert tones to direct the evacuation of occupants.
Unfortunately, residential buildings do not have persons who are available at all times to be a warden or who are willing to commit to this role. Typically, there is little or no warden structure in place for most high-rise residential buildings. Occupants are often untrained and may have little understanding of what differing tones mean.
As a result, the EWIS is used as an occupant warning system only, with little expectation that wardens will be in place. There is an assumption that by providing highly audible fire alarms, directional signage and fire exits, occupants will evacuate of their own accord. Unfortunately this is not always correct.

‘Wait and see’ approach
The reality for high-rise residential buildings is that there is a lack of motivation by occupants to evacuate. Many occupants will choose to ignore alert tones and just ‘wait and see’, feeling significantly safer in their unit if there is no direct threat from a fire. Occupants, having heard the alarm previously in their building and not evacuated, may interpret their past behaviour to be the correct action and remain in their apartment.
People living or sleeping within their apartment will generally feel safer within their fire-compartmented unit, rather than in the unknown conditions within stairwells or corridors. Residents who are on floors remote from the fire may decide not to evacuate until fire-fighters arrive, which could be 10 to 15 minutes into fire development. At this stage residents are probably safer within their unit.
Late evacuees can delay fire suppression, as the stairwell may need to be cleared before fire-fighting activities can start. Hoses and equipment can block a stairwell and the potential for smoke inhalation is greater as fire-fighters open doors to carry out fire-fighting activities.
A method of response to a fire emergency must be developed for high-rise residential buildings that can provide reliable outcomes and is closely aligned with the actual response of occupants and the risk to life from fire. A building evacuation system that can provide a more predictable methodology for occupants may result in safer residential buildings and lower building and compliance costs.
A review of international approaches to high-rise residential fire procedures has been conducted to determine the most effective procedure in a high-rise residential fire emergency. The review has indicated that two design methodologies currently exist across the world: (1) protect-in-place, and (2) evacuation (as currently operates in Australia).
Protect-in-place is based on the idea that residents are safer in their unit and should only evacuate if directly threatened by fire. All other occupants are expected to remain within their unit, unless told to evacuate by fire-fighting personnel.
The driving philosophy behind protect-in-place is that by not having to evacuate occupants, fire-fighters are able to carry out fast and effective suppression activities. Fire-fighting personnel would expect only a minimal number of residents to have evacuated, thus no search and rescue would be required by arriving fire-fighters other than in the unit of fire origin.
The concept of protect-in-place is not new, and has been practised for many years in both the UK and Hong Kong. Hong Kong provides a good example of the effectiveness of the methodology, as the city has one of the highest densities of tall residential buildings in the world. Its long history of successful protect-in-place implementation indicates that the strategy is effective.
The key argument against a protect-in-place strategy is that conditions are most tenable at the early stages of a fire; therefore, this is the best time to evacuate occupants. This is true and is not disputed. Unfortunately, for high-rise residential occupancies there is a significant pre-movement time for those who are going to evacuate, and a significant time taken to undertake the actual evacuation. As a result occupants may be evacuating in conditions that are poor and are getting worse. A protect-in-place methodology may even be safer for evacuees, minimising risks of trips, falls and smoke inhalation.
The outcomes from this study form part of a research project to ascertain the most effective approach for achieving safe and reliable outcomes from a fire event in a high-rise residential building. The protect-in-place methodology would appear to be a reaction to a fire emergency that is more closely aligned to the risk to life from fire, the real-life response of occupants and the actions of fire-fighters.
This study has been funded by the Fire Protection Association Australia (FPAA) through the Barry Lee Scholarship. For more information, or to purchase a full copy of David Barber’s paper, visit www.fpaa.com.au or call 1300 731 922.

 

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