Tolerancia a fallos

As high rise office buildings increase in height so does the distance an occupant has to travel from the floor which they occupy at the time of an evacuation alarm to a place of safety. The place of safety is normally outside or a place of refuge within the building36_{. A refuge in traditional terms is one that provides the necessary} shelter for a person who is unable to go down the stairs due to certain functional limitations 37Current amendments to NFPA 5000 (NFPA, 2012) will also permit the use of specially designed elevators. In the United Kingdom guidance is also given in BS5588 Part 2 on the design and installation of elevators for evacuation. These strategies may not always be entirely suitable for every type of emergency where it is possible that the elevators may be taken out of service. This PhD Study does not include an appraisal of alternative evacuation systems. It is only concerned about the use of stairs as part of a trial evacuation exercise most likely required by the relevant Occupational Health and Safety legislation in the light of the WTC 9/11 incident (Averill, 2005).

Research into emergency egress38 starting with the study of trial evacuations in the early 1970’s (Pauls, 1977) and the movement of crowds at the same time (Fruin, 1987) provided the building industry with valuable reference data. The two important aspects of the research was the match between the needs and characteristics of the occupant (individual office worker) and the egress stair and its surrounding environment (Pauls, 1977 and Bukowski, 2009).

International building regulations such as those in the UK, US, and Australasia created a surrounding environment for the stairs where these ‘egress’ stairs were required to be housed inside enclosed fire rated shafts that in the main led

36 _{E.g. Such as may be required by a Code such as the NFPA5000 Construction and Safety Code} (NFPA 2012) or D1/AS1 (NZ Department of Building and Housing, 2008)

37 _{Refuge and Fire resistance rating as defined in Approved Document B (Fire Safety – 2006 edition),} (Office of the Deputy Prime Minister (2010).

38 _{Emergency egress is the act of responding to and safely evacuating the area under threat to a place} of safety that is located either outside the building or within the building. The building needs to be designed with the necessary systems to allow this to happen.

directly to the outside of the building or discharged within a safe ground floor area39. This form of construction provided a fire resisting barrier to keep people safe as they passed the floor on which the fire was located and to prevent fire from spreading up through the building39. Other studies (Proulx et al, 2007) focussed on this challenging environment in terms of providing guidance for the individual in terms of signage and clearly defining the steps in each flight along with the handrails so that the individual could find their way and be provided with support for the such a challenging task (Reeves et al, 2008). More recent studies of two fire incidents (Proulx et al, 2004 and Kuligowski and Hoskins, 2010) show that safe egress involving going down the egress stairs depends on many other elements such as the emergency evacuation and response plan, the associated emergency communication systems and whether or not people are familiar with what they have to do. These two studies showed that the occupants were confused by a complex evacuation strategy and plan.

Office stairs were generally designed to accommodate two individuals to descend side by side (1100mm between walls or equivalent) (Pauls, 1984). This minimum width was based on data gathered over 40 years ago. Pauls has challenged this width based on findings from the WTC 9/11 incident and has shown that this width should be increased to between 1200-1500mm (Pauls et al, 2007). Pauls is supported by other studies such as that of Blair (2010). Pauls et al (2007) maintain that the characteristics of the individual have changed over the last 40 years especially in terms of lifestyle both at work and at home. They (Pauls et al, 2007) simply state that the average body size has changed due to obesity and that people are not as fit as they used to be. Some people are still fit and therefore can go down the stairs at a faster rate than others who are less fit and able. Stairs need to be wider to allow the fitter people to overtake and to allow fire-fighters and other emergency personnel room to climb up the stairs so that they can rescue other occupants who may be trapped on a higher level. The need to increase the minimum width has been confirmed in a more recent study carried out as a result of two main studies the first

39 _{Part 24, Former Australian Model Code developed by the Interstate Standing Committee on} Uniform Building Regulations prior to 1979.

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by Galea et al (2008) being the UK Study of the WTC 9/11 incident40 and the second by Peacock et al, (2009) where they showed that the width of the stairs was one of the main reasons for increases in evacuation time.

Peacock et al (2009) also showed that there were still other things that required further research and this was confirmed by Blair (2010) in a separate study using the same raw data from the Peacock et al study (2009). In analysing the data she found that the data was extremely ‘noisy’ due to other behavioural factors41 that she was not able to examine any further. One of the examples of this ‘behaviour’ which has been studied recently is the interaction of the individual with others in such actions as ‘merging’ when entering the stairs (Boyce et al, 2011). Survivor responses from the WTC9/11 Incident (Dwyer and Flynn, 2004) show the marked presence of other forms of group such as altruistic behaviour42. This type of behaviour can cause the group to go down the stairs at a slower rate (Fahy and Proulx, 2005) and possibly test the patience of those behind by holding them up (Parker-Pope, 2008). Conversely it should be noted here that a member of the group may be too embarrassed to ask the others in the group to slow down so that this member may increase their risk of falling by travelling at a faster rate43_{. Group} behaviour can even be affected by the emergency evacuation plan where special provisions are made for an individual requiring assistance to be assisted by their work colleagues or other specially trained workers (Kuligowski and Hoskins, 2011). One of the recommendations made from an analysis of the WTC9/11 Incident made in two separate studies was the importance of the occupants and their

40 _{Galea et al, (2008) mentioned how people were held up by fire-fighters and other emergency} responders – problem of counter flow.

41 _{Behavioural factors in trial evacuations are the major concern of the thesis, but the number of other} factors may quite well increase during an actual emergency. An example of occupant confusion caused by a complex evacuation and alarm system in a real fire is presented by Proulx and Reid, (2006).

42 _{Altruistic behaviour here means when members of the group are prepared to and do help another} member of their group with some kind of impairment or functional limitation.

43 _{Increasing walking speed for mature workers increases the risk of falling due to tripping (Loo-} Morrey and Jeffries, 2006). This is to be explored further as part of the PhD Study via the use of Focus Groups.

organisations being prepared for an emergency (Gershon et al, 2007 and Averill et al, 2005). The recommendations from these two studies showed the importance of training where the occupants actually completed the evacuation task in its entirety and that this should be done regularly and that if that involved going down the stairs then the occupants should do so. This would be the only way for everyone to find out whether they were able to cope with the physical challenge of going down the stairs or whether they should be evacuated in another way (wait at a safe refuge, evacuate by properly designed elevator or by some other means) (Gershon et al, 2008). Completion of the evacuation task therefore involves trial or practice evacuations carried out at least once or twice per year.

Emergency preparedness centred on trial evacuations is now a legal requirement for high rise office buildings in such countries as the US, UK and Australasia. This requirement is typically either enshrined in a performance requirement such as in Section 21 of the Model Occupational Safety and Health Code for Australia (Safe Work Australia, 2011) or via a set of prescriptive regulations such as the New Zealand Fire Safety and Evacuation of Buildings Regulations (Department of Internal Affairs, 2008). Where the requirement is performance based (i.e. the employer is required to provide a safe place of work) this is usually reinforced with a Code such as the Australian Standard AS 3745:2010 (Standards Australia, 2010). Usually the occupants are required to practice the implemented procedures at least once or twice per year such as in New Zealand (Department of Internal Affairs, 2008). The UK Fire Safety Reform Order requires fire risk assessment of buildings from time to time. This assessment will involve the development of evacuation strategies and the associated planning and training. The employee is required to participate in the practice evacuation and this means that this participation is one of the conditions of employment (DCLG, 2007).

Gwynne (2008) shows that evacuation procedures need to be inclusive. This means that the occupant needs to be consulted and become involved in the preparation of their own plan. Guidelines already exist in the UK for the preparation

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of such a personal emergency evacuation plan (PEEPS44) (DCLG, 2007a) which cater for those with certain designated ‘disabilities’.

The question can be asked as to whether the term “disability” encompasses all the individual characteristics that would place any particular individual at risk going down the stairs twice per year. Some of the functional limitations such as sarcopenia and its associated causes mentioned by Al-Abdulwahab (1999) may not be included or be readily apparent in the definition of disability (e.g. NFPA, 2007). Many studies link lack of fitness, especially for those over the age of 40 years, to such things as strength and stability (Bergland et al, 2008; Browning and Kram, 2008 and Corbeil et al, 2001) so that there may be a greater risk to the individual and also others in their group in requiring any occupant to use the stairs in every trial evacuation which would be held at least once or even twice per annum. This risk may be greater than that associated with a lesser frequency which is during an actual emergency. This is seen as the research question as discussed in Chapter 1.