High rise building emergency evacuation
Mr. R.R. Nair, Chief Executive, Safety and Health Information Bureau, Vashi, Navi Mumbai.
Holds Master’s Degree in Economics, Post-Graduate Degree in Library and Information Science and a Diploma in Computer Management. Has more than 50 years of experience in the field of OSH.
The article highlights on issues involved in evacuating the occupants from high rise buildings in the event of a major fire. It gives an outline on various evacuation strategies adopted such as: total building evacuation, progressive evacuation, phased evacuation, partial evacuation, self-evacuation and stay-in-place approach. It also gives a brief description about various new rescue devices such as: rescue chutes, suspended rescue platform system, controlled descent devices, non-structured dependent devices, wheelchair stair climbers & evacuation chairs for mobility impaired, etc.… used in the safe evacuation of occupants from high rise buildings.
Fire Safety is one of the prime importance of the day. Fire incident is every day’s news. As per National Crime Records Bureau, 20,377 cases of fire incidents reported in India for the year 2014, involving 19,513 deaths and 1889 injuries. Many of these deaths could have been prevented.
A fire can pose very high risk to life and property of its occupants. Fire creates total waste. Such waste would not be tolerated by any Nation. The magnitude of fire incidents can be reduced only when the building and structures are designed, constructed, equipped, maintained and operated so as to save life and property of its occupants. The fire at Lotus Business Park building in Andheri (W) on the 18th, July 2014 (See Fig 1) was one clear example, of flouting the fire safety norms. Any structure or building should be erected only after meeting the basic infrastructure needed to protect them from fire and explosion, and even to withstand natural calamities like earthquake, cyclone, lightening, etc. When it comes to high-rise buildings, the problem becomes more complex and need meticulous planning.
The term High Rise Buildings is also known as “Skyscrapers”, “Towers”, “Tall Buildings”. Fig 2 shows a comparison of World’s 14 tallest buildings. The definition of high-rise building vary from country to country or region to region. For example:
The International Conference on Fire Safety in High-Rise Buildings defined as high-rise as “any structure where the height can have a serious impact on evacuation”. According to Emporis Standard (ESN 18727), a high-rise building is “a multi-story structure between 35-100 meters tall, or a building of unknown height from 12-39 floors”.
The National Fire Protection Association of USA defines (NFPA 101, Life Safety Code, 2012 edition): “high rise buildings as a building greater than 75 feet (23 m) in height, where the building height is measured from the lowest level of fire department vehicle access to the floor of the highest floor occupiable story”. A height of 75 feet translates into roughly seven stories.
As per the International Building Code: “high rise will be 75 feet to 450 feet” and everything above will be categorized as “Super High Rise”.
As per the National Building Code of India (NBC), 2005, “all buildings 15 m or above in height as high rise building”. This definition has been followed by all fire statutes brought out in India, except Development Control Regulations issued by few local bodies, who have regarded 24 m as high rise.
High-rise buildings have been rising day by day in city skylines of India. There is no comprehensive data available on the number of high-rise buildings existing in India. Cities like, Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Kochi, Kolkata, Mumbai, Navi Mumbai and Surat have witnessed vibrant growth of high-rise buildings. Mumbai-Pune regions alone accounts for about 5000 high-rise buildings.
The tall buildings have unique features which can adversely affect the fire safety of a building. These features include: height beyond available resources of local fire brigade ladder; extended evacuation time; pronounced stack effect; water supply limitations; mixed occupancies; iconic nature, etc. However, this article will focus only on various methods of evacuation strategies followed and new rescue devices available for safe evacuation of high rise buildings.
2.0 EVACUATION STRATEGIES
In the event of a fire, its occupants need to know what action should be taken to leave the building safely along protected escape route. In very tall buildings, full building evacuation via stairways might be impracticable in the event of a fire. Many evacuation strategies have been developed and experimented in many countries and few of them are listed below. Due to limitations of space, only salient aspects of these strategies are discussed here:
- Total Building Evacuation;
- Progressive Evacuation;
- Phased Evacuation;
- Partial Evacuation;
- Self-Evacuation; and
- Stay-in-place Approach.
2.1 Total Building Evacuation
Total evacuation involves the evacuation of all building occupants at once from a building to an outside area of refuge or safety. Once the alarm signal is sounded, all building occupants are expected to evacuate to the staircases which lead to the ground floor. During a total evacuation, elevators would collect occupants from the highest floors first, shuttle them to the exit level and return for another load. Even elevators could be programmed to move those with the longest distance to go first.
Occupants evacuating in stairs could be exposed to other kinds of dangers such as tiredness, becoming dizzy or slipping on surfaces, especially when descending thousands of steps of stairs in high-rise buildings. The large number of occupants descending down the staircase may also hamper the fire-fighting access to the fire floor through staircases. Although the total evacuation is the simplest strategy to implement, it is usually only ordered by the fire department.
2.2 Progressive Evacuation
In progressive evacuation, occupants can remain in the rescue area or area of rescue assistance, for a period before evacuating the building, either by themselves or with assistance from emergency responders or others. Occupants are only evacuated from the building to the exterior as a last resort. The relocation of occupants can either be horizontal – to an adjacent compartment on the same floor, or it could be vertically to a dedicated region further down the building from the fire floor i.e., a refuge area/floor. Progressive evacuation might be used for occupants with disabilities.
2.3 Phased Evacuation
In phased evacuation, the occupants on the most critical floors like fire floor and floors nearby will be evacuated first. Only the occupants within the compartment on fire, need to be evacuated from the building immediately. The remaining occupants of the building are evacuated subsequently as necessary. Of course they need to be alerted about the incidents. Many high-rise buildings in the world uses phased evacuation in case of fire. Controlled phase evacuation is relatively complex. The concept of phased evacuation relies heavily on sophisticated communication system and training. In phased evacuation queuing time into staircases can be reduced.
2.4 Partial Evacuation
Partial evacuation is also known as “zoned evacuation” or “staged evacuation”. It provides for immediate, general evacuation of the areas of the building, nearest the fire incident. A partial evacuation may be appropriate, when the building fire protection features assure that the occupants away from the evacuation zone, will be protected from the effects of the fire for a reasonable time. Evacuation of additional zones may be necessary, in the event that a fire or smoke condition exists. In such cases, occupants will evacuate at least two floors below the fire floor, re-enter the zone, and wait for instructions.
Self-evacuation refers to occupants evacuating by themselves, before emergency responders have arrived on site, using available means of evacuation, i.e. elevators and stairs.
2.6 Stay-In-Place Approach
In Stay-in-place, the occupants remaining in the room with an exterior window, a telephone, and a solid or fire resistant door. In case of a fire, when all exits from a floor are blocked, the occupants should go back to their room, close the door and seal the cracks, wave something at the windows and phone for help. Stay-in-place evacuation approach is generally used for evacuating the disabled occupants.
3.0 ESCAPE EQUIPMENT
As the vertical height of the buildings are going up day by day and the evacuation becomes difficult, many new rescue devices are being developed and tried. Some of the new rescue devices tried for high rise evacuation are:
- Rescue Chutes;
- Suspended Rescue Platform System (SRP);
- Controlled Descent Devices (CDDs); and
- Non-Structural Dependent Device.
3.1 Rescue Chutes
Fire escape chute is an emergency exit that permits rapid, mass evacuation from high-rise buildings during life threatening emergencies. Escape chutes can be used from most high areas, where there is a possibility of being trapped by fire, terrorism, criminal attack, that could result in the event of life or serious injury due to non-availability of alternative means of emergency egress. Escape chutes today are becoming an accepted alternative means of emergency evacuation from high-rise buildings and industrial plants. Escape chutes are now available in various formats that allow evacuees to descend vertically or slide down.
The chute is a cylindrical or trough shaped device, typically made of fire resistance fabric or netting (See Fig 3). As it is set at an angle, people can slide through it without difficulty. The upper end of the tube enters the room. When fire is discovered, the people in the building sit in the upper part of the tube, slide down it, and land on the ground below. Some of the benefits of the fire escape chute are:
- Capacity to evacuate about 30 people a minute;
- Descent 50 floors in about 100 seconds;
- Chute access from every floor; and
- Protection for evacuees and any physical condition.
3.2 Suspended Rescue Platform System (SRP)
A suspended rescue platform system is defined as “an enclosed platform (cabin) or set of enclosed platforms, moving along guides or other means, on the exterior of a building, intended for the evacuation of multiple occupants from a building”. An escape rescue system is a building-wide system composed of two or more devices; each is an array of five collapsible cabins (See Fig 4). The system is permanently stored on the roof in a folded position. Upon deployment, each array is lowered to the ground. It then unfolds, enabling emergency responders to board the cabins. Two arrays will evacuate 300 people simultaneously. Each array is then lowered to the ground and the evacuees exit as it refolds. The system repeats this cycle, transporting responders up and into the building and evacuating occupants as required. The Platform-based systems enjoy a number of prominent advantages:
- They are effective for all building heights;
- They require no special skill or unfamiliar actions by evacuees;
- They are “systemic” (building-wide) solutions;
- They are suitable for all ages and physical conditions of evacuees, including disabled people;
- They have the ability to transport emergency responders and their equipment up and into the scene;
- They enable rescue personnel to control the evacuation process; &
- They can evacuate many occupants with each rescue cycle.
3.3 Controlled Descent Devices (CDDs)
The Controlled Descent Devices (CDDs) are escape systems that use a simple harness, cable and breaking device to control the rate of descent. A CDD is an equipment designed to accomplish the withdrawal (emergency egress) of occupants from a building and transporting them from a dangerous area to a safe area (See Fig 5). CDDs may be automatic or manually operated. Persons may use CDDs, acting by themselves or with the assistance of others. CDDs are permanently installed, usually near a window, or a balcony, or near another exterior exit point that may be used for egress in an emergency.
3.4 Non-Structured Dependent Device
Non-Structured Dependent Devices are escape systems that do not require contact points with the building or the ground during descent. This can be best described as parachute and process for escape in similar to base jumping.
4.0 OTHER DEVICES USED
4.1 Evacuation of Mobility Impaired
The traditional view of mobility impairment is that of occupants confined to wheelchairs or similar devices. There are a variety of conditions that may require an alternative egress plan to be sought, for example, those with temporary disabilities, e.g. broken limbs, sports injuries, pregnancy, etc. Adequate provisions for the evacuation of mobility impaired occupants is a fundamental requirement in all buildings – whether tall or not. In tall buildings, special consideration for their protection should be considered. Injured, infants, aged or disabled occupants can be now safely evacuated using special devices such as Evacuation Chairs, Wheelchair Stair Climbers (See Fig 6).
4.2 Helicopter / Rooftop Helipads
In certain cases, helicopters have been successfully used to assist with building evacuations. Many tall buildings are provided with helipads as part of the building’s functional use, for example, a hospital or a high end residential/hotel/office. In such situations, the use of helipad would be a good additional safety feature. However, there were difference of opinions amongst the professionals on the use of helicopters in high-rise building firefighting operations.
Fire authorities often insists for the provision of helipads on tall buildings, for the purposes of both occupant evacuation and firefighting operations. As per NBC, 2005, Part-4 Annex C-10, provision for helipad should be made for high rise buildings above 60 m in height. However, use of helicopters have many limitations, like: the number of people that can be evacuated by helicopter in a single trip is usually relatively small; the rescue operation must be carefully planned and executed; the landing of helicopter on the roof of a burning building is, in itself, an extremely dangerous operation; lack of visibility due to smoke or high winds could make it difficult for the helicopter to land.
In India, every year about 20,000 persons die in fires. Fire Safety is one of the prime importance of the day. High rise building have been rising day by day in city skylines of India. The tall buildings have unique features, which can adversely affect the fire safety of a building. In every tall buildings, evacuation via stairways might be impracticable. Thus, many new strategies have been developed for safe evacuation of high rise buildings and amongst them phased evacuation may be more appropriate. Similarly many new rescue devices are also available. NFPA and ASTM has recognized some of the escape devices as supplemental evacuation devices. The use of such devices may not be recommended as a permanent alternative to the use of stairways or elevators.