The Gray Monk

High Rise fire protection.
A case for joined up solutions

A paper prepared for the Conference Fire Safety of High Rise Buildings
7th to 10th May 2008
Bucharest, Romania
By
Patrick G Cox
MA, BSc, FIFireE, ASAESI, AIOSH, CFEI, CFII

Introduction

There is generally no accepted definition of a “High Rise” building. Some Countries such as the UK originally based their definition on the height of the longest ladder in use by fire and rescue services, but it has never been shown to be a truly practical determination since it is based on the assumption that, on any building below this height, it is possible to fight a fire in the building using ladders pitched from the street or the ground alongside it. An argument could be made for a reduction of this height to 18 metres since fire services no longer carry ladders of fifty feet (15 metres) length and cannot “extend” these by adding a single 10 feet (3 metre) ladder to the head. For firefighting purposes, a high rise building can be considered to be one containing floors at such a height, position or design that external firefighting and rescue operations may not be feasible or practicable.

The current trend to build taller and taller buildings presents many challenges for the designer, the developer and the safety engineer. There are many reasons why tall buildings are attractive to developers, not least that they offer a very good return on investment if the developer is able to maximise the land use in a prime location such as a city centre. However, modern construction systems, structural materials, internal arrangement and linings coupled with population loading and use of the building create many problems to be solved by the fire safety specialist. Not least is the problem of fire spread upwards through such a structure via the face of the building, service ducts, air-conditioning ducts and other shafts. Once the fire begins to spread above the storey of origin it rapidly becomes difficult, if not impossible, for the fire fighters to prevent it continuing all the way to the uppermost storey.

In 1908 the then Chief of the New York Fire Department declared that the race to build ever taller buildings in his city would soon result in a situation in which lives would be lost because his department could not reach the fire floor with effective water streams or ladders. Fortunately he was listened to by those in authority and the legislature began to look seriously at the problems and many of the solutions they determined are still valid – but not always followed. As the events of September the 11th showed in New York, some things simply cannot be designed for. However, it must be said that the structural fire protection and safety systems performed well enough in extraordinary circumstances there to significantly reduce the actual loss of life.

Several questions must be addressed in designing a modern high-rise structure for safe use, not least the consideration which must be given to access and facilities for fire fighters. A number of recent projects have shown that there are severe limits to what can be expected of fire fighters entering these structures to fight fires, yet, the majority of regulations framed for fire protection and life safety are based on data that is sixty or more years old and of questionable value in buildings where the materials used as linings, furnishings and fixtures may be synthetic or composites with a high proportion of synthetic materials added.

Fire fighters now wear protective clothing which provides far greater thermal protection than was possible a generation ago. While this affords better thermal insulation for the wearer it is balanced by retaining the wearer’s body heat as it is generated by exertion, thus raising the wearer’s core body temperature. At the same time, changes in design and in the materials involved in the fires the fire fighter must confront have resulted in fires that are faster in development and in thermal output. Better understanding of the effects of heat and dehydration on fire fighters has driven a re-evaluation of fire fighting tactics in many countries, yet the legislation regulating building standards still permits reduction in protection of a given structure in some circumstances where, if consideration had been given to the contents and use, it might not have been considered appropriate to do so.

High rise structures are the future built environment, however, what is needed is a careful reappraisal of the entire suite of building regulations governing such structures and the data which underpins them. Only by applying the most up to date information and addressing the issues this raises can we ensure a safe environment for the future.

Construction methods and problems

As one moves around the globe one discovers that structures, especially high rise structures, tend to be constructed in a number of different ways. Some are constructed in steel and glass, some in concrete and some in a mixture of both. Technically, reading the UK Building Regulations or the Scottish Technical Standards, it is possible to gain approval for an all timber structure of over ten storeys – a high rise structure. Fortunately perhaps, it would be prohibitively expensive to build one.

Inevitably the use of curtain wall structures results in a gap between floor slab and curtain. This is recognised and there are many different methods for protecting these gaps. Unfortunately it is often the case that other services may be overlaid on the gap and the closure and, in some cases, compromise it. Ventilation systems require the provision of ducts and plenums and these, in turn, present several challenges in addressing the fire protection of compartments and floors. The extensive use of electronic equipment in modern buildings requires the provision of far more cabling than was the case one or two generations ago, and the cable insulation introduces a fire load that is often overlooked as it is often concealed in voids or plastic ducts.

While a structure may, at first glance, appear to be a Class A (UK classification) or a Type I or II (NFPA 220 Classification) structure, essentially a “non-combustible” building, the internal fittings and furnishings will almost certainly change that to a lower rating in real terms. The use of dry linings and partitions introduces other hazards as well, including formaldehyde and several other toxic chemicals which are released in the event of a fire. This was the case in Sao Paulo in the 1960’s when the Joelma building, structurally concrete and steel, was almost entirely gutted by fire with a high loss of life – due almost entirely to the internal linings and furnishings. It is worth noting too that the fire severely damaged the concrete and steel structure and proved impossible to fight from the outside of the building or from street level.

Protected shafts and stairs are now recognised as a necessity in high rise buildings, but, again, there are different approaches to the provision of the protection. It has to be recognised that lobbied approaches to stairs and lifts take up valuable, to the developer, letable floor area. Typically, a lobbied 1 metre wide staircase occupies roughly 16m2 of floor area. Unsurprisingly therefore, there is always pressure to reduce the number of staircases required for means of escape. This, in turn raises another question for high rise designers – can the lifts be incorporated into the means of escape, and if so, how? Again, this means that the lifts have to become a part of a “protected” zone and measures have to be in place to ensure that this cannot be compromised or the power to the lifts fail. Then there is the question of lifts “sharing” shafts and using a “parking” system to allow loading and unloading while another lift car bypasses the “parked” unit. Some use is also made of “double-decker” cars in some very tall structures and these present further challenges for the fire protection engineer.

Modern services require the provision of ducts and service shafts which may form flues and provide channels for the spread of fire between floors and compartments. Again, these can be protected, but what is less well regulated is the maintenance of the protection during the life of the structure. The fact that it was provided on completion does not necessarily mean it will still be in place a few months or years later. In similar vein, modern high rise buildings almost invariably make use of suspended ceilings to permit the housing of services and the fitting of lighting systems. Raised floors, intended to provide a service area for computer cables and other services beneath a “working” floor provides yet another “hidden” space. These create large voids and care is required to ensure that these do not compromise the fire protection and other safety systems.

Every shaft, duct or staircase needs to be protected, and atria need special attention as all these features can rapidly become a flue in a fire, spreading the heat, smoke and ultimately flames upward.

Innovative construction

Sometimes it seems that each new high-rise project is setting out to “out innovate” the previous one. Each new mega project, such as the giant sail structure in Dubai, requires creative and innovative use of materials to achieve the strength and stability necessary. Necessarily this means that much of the structural framework will be “in tension” and any failure within a major element of the structure could trigger a catastrophic failure of the entire structure. An example is the 9/11 collapse, triggered by the failure of the external fastenings supporting the floor slabs above the fire and impact area.

Large atria connecting the ground floor to several – and in some cases all – storeys require very careful planning as they can very easily become the means by which a fire can overwhelm the buildings defences. Atria now feature in many very large buildings and in some extend the full height of the structure providing both light and ventilation to areas and floors which may well be difficult to service in other ways.

Nor should we overlook the “innovation” using fabric materials as internal ceilings, decorative blinds and screen and other “features” decorative or otherwise. The use of aluminium and light metal alloys in structures presents a number of problems for fire protection while solving several for the structural engineer. “All glass” curtain walling, while not “innovative” in today’s constructions, may well be coupled, as in the Lloyds Underwriters building in London, with an external load bearing frame and services such as ducting, lifts, stairways and heating.

The desire to go higher and to combine this with very large open public spaces presents a number of challenges for fire protection and requires a very thorough appraisal of the likely fire load and the most effective means to deal with it. In short, innovative designs frequently require a very flexible and innovative approach to fire protection. The advent of “super high rise” structures calls into question all the current thinking on evacuation systems. Compartmentation, active fire fighting systems and fire engineered systems for evacuation are no longer “nice to have” but vital components of a much more complex solution to occupant safety.

Modern materials

Modern construction materials embrace a number of “new” materials which were not in common use at the time the data on which the majority of current modern Building Regulations are based. In the UK, much reference is made to “Post War Building Studies, however, much of this data was collected and collated in the period 1920 – 1939 and is based on fires involving timber, natural fibres and limited plastics. Since the 1960’s the trend has been to make greater use of plastics and other materials including wood chip, compressed fibres and other “boards” in both furniture and structural elements. Aluminium curtain walling systems introduced for high rise structures are known to fail once flame impinges on them and can result in large sheets of glass being released to fall into the street below.

Steel provides a great deal of structural strength in construction on a weight/strength basis, but this is rapidly lost if the steel is exposed to fire and reaches temperatures above 6000C, a relatively low temperature in most fires. Concrete overcomes some of that problem, but relies on steel “rebars” embedded within the concrete to provide stability and strength in tension. Provided the steel is buried to a suitable depth (generally considered to be not less than 25mm) in the concrete, it will maintain its integrity and strength for longer than steel. However, once heated, it may spall explosively if subjected to a sudden thermal shock such as sudden rapid cooling due to fire fighting. Pre-stressed concrete “planks” also provide a lightweight alternative to poured floor slabs and more recently the use of lightweight “profiled” steel forms covered by several centimetres of concrete provide another light solution to the creation of tall buildings.

Many modern boards used in internal linings, partitions or finishing include resins and plasticizers. Typically “melamine” is a trade name for a type of “chipboard” finished with a plastic coating which is both durable and washable. While not easily ignited, it will burn fiercely and emit toxic fumes and products due to the fact that the board making process makes use of formaldehyde to prevent fungal and insect attack on the board. PVC based plastics produce toxic and corrosive products when burned and burn fiercely giving a very high thermal output weight for weight.

Passive fire protection

Passive fire protection is provided by the installation of fire rated doors, the closure of openings in walls required to provide compartmentation, enclosure of ducts, plenums and the subdivision of any voids. It seeks to confine any fire to the compartment or area of origin and to restrict spread either laterally or vertically through a building. A very wide range of methods are available and include coatings for steel structural members to prevent direct flame impingement on the member, intumescent materials in the form of collars to fit round pipes, closing devices for fitting inside ducts and “curtains” to prevent lateral spread of smoke and heat in voids.

The effectiveness of passive fire protection depends firstly upon how well it has been installed but is then very dependent upon being maintained correctly throughout its life. A typical example is that of the “fire resisting door” which, installed in the correctly rated frame and with the approved door furniture, is capable of withstanding a fire for a rated period. However, if the door is damaged, by the removal of the smoke seal, or through being wedged open against its closing device and warps, the integrity of the door will be compromised and may not prevent the passage of fire. Likewise, a wall constructed correctly to a fire resisting standard may be compromised by a plumber or electrician cutting a hole through which to pass a pipe or cable, and then failing to seal the opening with the appropriate fire rated sealant.

Regulation and Fire Protection Requirements

Most national jurisdictions have established Building Regulations, Standards for Construction and Codes of Practice for fire protection. These will incorporate requirements for the safety of occupants, the structural protection of the building, for stability of structures, for drainage and such matters as heating, lighting and ventilation. Most address a wide range of buildings and more and more commonly allow the use of standards or codes from a different jurisdiction if “equivalence” can be proved. What must never be forgotten in dealing with any Building Code is that it is NOT a maximum standard, but a MINIMUM.

High-rise structures present the designer and fire safety specialist with several challenges in this regard since most require the use of “fire engineering” to address all the requirements for life safety. The balance between building to minimum tolerances and strengths structurally can impose a need to design the fire protection systems to a higher standard in order to achieve the level of protection required.

Means of Escape requirements

The modern requirements for the provision of “means of escape” (Egress in American Codes) have their origins in studies done in a number of countries in the 19th Century. It was established that a travel distance of one hundred feet in an unprotected escape route was the maximum distance any person could expect to negotiate safely in the time between becoming aware of the fire and their attempting to escape. It was further found that this is affected by the persons training, or lack of, ambulatory ability and conditioned responses. The width of exits was also studied and it was found that a width equivalent to a width of a man’s shoulders was the absolute minimum and that a width roughly equal to four men abreast was the maximum.

Subsequent studies have shown that these figures can be translated into reality and further studies have focussed on the human behavioural aspects of escape from danger. In high-rise structures this means that a great deal of thought needs to be given to the position of the escape stairs or – if it is intended (as in the Petronas Towers and more recent structures in Taiwan) that the lifts be considered part of the means of escape – the position of and availability of lifts.

Thinking behind risers and water supplies

In general, most codes, regulations and standards require that any building over eighteen metres be provided with a “riser or fire main” (In the US Codes a “Standpipe”) internally installed in the staircases with outlets for fire fighting at each floor. In the UK in buildings up to sixty metres this may be “dry”, that is, not connected to a permanent water supply, and provided with an inlet allowing the fire appliance pump to supply water directly to the riser when needed. Over sixty metres fire mains are generally required to be “wet” and left permanently charged to speed extinguishing operations. The idea was that in smaller buildings a fire hose could be laid up the fire service ladder and the fire fought through the windows or from the exterior. In taller buildings mechanical turntable ladders could also provide an exterior attack to the fire from outside the building. Beyond the reach of this equipment and subject to the nature of the exterior envelope of the buildings fire fighters are dependent upon entering the building to fight the fire from the staircase.

The UK regulations, up until 2006, required a maximum pressure of 4- 5 bar at the outlet for wet risers installed in buildings in the UK. In the case of dry fire mains the pressure available at the outlet of the fire main is dependent upon the choice of firefighting branch, diameter of hose used and the charging pressure for the fire main. This was sufficient pressure for the equipment in use until 1960, however, since then, buildings and the materials in them have changed dramatically and so has fire fighting equipment and procedures. The regulations have not; however, BS 9990: 2006 has introduced new requirements which go some way to addressing these concerns.

Access for fire fighting

High-rise buildings in particular present a number of challenges with regard to access for fire fighting or rescue. Podium type buildings, with the lower storeys projecting some distance from the base of the “tower” section, generally preclude the use of any high-reach appliance such as an Hydraulic Platform, Turntable Ladder or the newer hybrids. UK building regulations require access to an entry point for a pump appliance within eighteen metres of the building, this to allow the connection of fire hose to any inlet connections for risers or for tanks supplying the risers. The requirement generally also requires a “line of sight” to enable the pump operator to see the entrance and the connection points so that they are aware at all times of the state of operations.

Where the buildings stands away from public thoroughfares there may also be a need to provide for “hard standing” on the access surfaces so that appliances of up to sixteen tons can be operated safely. Again, this requires a made-up surface to provide a safe operating environment for the fire appliances and their crews while the emergency is dealt with.

Sprinklers, ventilation and fire detection

Currently in the UK, any building over thirty metres in height must be fitted with a sprinkler system and this is reflected in many other national codes. This is again related to the early studies which found that the time consumed in reaching the fire floor, if it was above this height, and in laying out fire hose coupled with the effort required, meant that fire fighting was generally fairly restricted.

Ventilation, or “climate control”, systems fitted to provide occupant comfort may also be used to control the movement of smoke or to extract it from the fire floor. Consideration needs to be given to the interaction of these systems and the sprinklers and to the circulation of smoke to uninvolved floors and compartments by the system. The experience of the MGM Grand Hotel in Las Vegas highlighted the need to ensure that any such system does not ingest and circulate the smoke from one area into an otherwise protected area.

Fire detection systems have an important, if not vital, part in the protection of any high-rise structure. A properly designed fire detection system can give sufficiently early warning of a fire to allow the occupants to escape and to alert the fire services, allowing them to respond early. Such a system forms a vital part of any “fire engineered solution” and is the control device which actuates smoke curtains in malls or atria, switches HVAC systems to extraction mode and opens vents. It can also “pre-action” a sprinkler system and close fire doors or open doors locked for security purposes. As with every such system however, maintenance is essential to reliable operation.

Physiological constraints on fire fighters

Better protective clothing for fire fighters has led many to think that this means that the fire fighter is now able to penetrate further into a building and enter compartments where the temperatures were previously non-survivable. Nothing could be further from the truth, as has been demonstrated by a comprehensive study carried out in the United Kingdom by the Fire and Resilience Directorate’s Research and Statistics Division, under the broad title of Building Disaster Assessment Group. A team of scientists and fire officers carried out wide ranging research into a number of aspects of modern building fires, protective clothing and fire fighting equipment. Their findings may be accessed online through the Department of Communities and Local Government website.

Building Disaster Assessment Group (BDAG) Reports

The BDAG team looked at several actual incidents including Collection and Analysis of Emergency Services Data Relating to the Evacuation of the World Trade Centre Towers of 11 September 2001” (Galea E R and Dixon A J P University of Greenwich), “Physiological Assessment of Fire Fighting, Search and Rescue in the Built Environment” (Optimal Performance Ltd; Dec 2004 for the Office of the Deputy Prime Minister) and Effect of Reduced Pressures on performance of firefighting branches in tall buildings – Aspects of High Rise Firefighting (Hunt and Roberts, December 2004 Office of the Deputy Prime Minister). These reports highlighted a number of matters which have a serious impact on High Rise structures, not least being: -

• Evacuation and life safety of occupants,
• Access and penetration limits for fire fighting,
• Maintenance of systems and integrity of fire resisting elements,
• Management of fire risk and introduction of hazards,
• The dynamic nature of fire risk and fire and life safety in any built environment,
• Interdependence of “passive” and “active” fire protection,
• The speed of fire development and heat output for modern synthetic materials have changed fire behaviour in modern offices and other buildings, and
• The physiological demands on fire fighters impairs performance,

Among the most important findings highlighted in these reports is the physiological strain placed upon fire fighters during fire fighting and search and rescue activity in any structure. The better protection afforded by the latest personal protective clothing can create a sense of false security and lead to fire fighters penetrating further into a building under conditions that are beyond safe exposure limits. It was found that, when coupled with already raised heart rates and body temperature due to exertion in reaching the fire floor, performance and judgement may already be seriously impaired.

In addition it was found that water pressures stipulated in most Building Codes and regulations are no longer in line with the working pressures required for optimum performance of modern equipment. This has resulted in a change in operational procedures in use in the UK, where it was found that using a larger bore hose (51mm instead of 45mm) could offset, to a limited extent, the lower operating pressure in the riser. However, this is a matter which requires serious thought and should be the focus of a determined drive to amend the relevant sections of all codes and regulations.

Many, if not all, of the matters identified in these reports have been advised to the fire and rescue services through the medium of Integrated Risk Management Procedure (IRMP) Guidance Note No.4 and a Fire and Rescues Services Circular (FRSC) Number 55/2004.

Protection of fire fighters

An aspect of the BDAG study included an assessment of the protection afforded by a number of different materials and “systems” for assembling protective clothing for fire fighters. It was found that there was a “trade off” between the enhanced protection afforded and the retention of body heat by the wearer. This means, in short, that the body heat generated by the wearer during periods of exertion cannot, effectively, be dissipated. This gives rise to an elevation of the wearer’s core body temperature, which, once it rises above 390C, can result in impaired performance and loss of mental awareness. This is of particular concern where fire fighters are required to expend a considerable effort in order to reach the fire floor and are then expected to penetrate into the fire compartment with an already elevated core body temperature.

Penetration into a building

It is assumed in many codes and building regulations that fire fighters will be able to penetrate between 45 and 60 metres into a burning compartment and perform rescue and firefighting activities. The BDAG studies found that this is not the case and that the elevated core body temperatures coupled with exertion severely restrict the ability of the fire fighter to carry out rescue and penetrate further than between 18 and 30 metres even with the best possible level of personal protection afforded by the PPE.

Rescue and refuges

The need to provide access for the ambulatory impaired worker and visitors to these buildings requires that special provision must be made for their safety in the event of fire or other disaster. To this end “refuge” areas are generally provided where wheelchair users may be “parked” to await rescue. The outcomes of several trials in evacuation show that the physiological strain this places on the rescuers needs to be considered very carefully when planning these.

The case for active fire protection systems

There can be no doubt that, in the light of the trend towards higher buildings and the use of modern and innovative construction systems and design of buildings, the nature of the fire that may arise is very different to that which, even twenty years ago, was likely to be encountered. The BDAG research clearly shows that the physiological limits for the fire fighter are a matter for serious concern everywhere, never more so than in structures where the physical exertion required to reach the fire floor and the fire are likely to push the fire fighter to the limit of their endurance. We must also recognise that the World Trade Centre event was unusual and that there is almost no practical defence against such an attack on any building. That said, the measures provided for the evacuation and fire defences performed as intended, even though the fire was far beyond their designed capacity.

Building Codes and Regulations need to be updated to take account of the data now available. Regulators and regulating bodies need to take account of lessons learned in all too many fire disasters to ensure that not only are these structures given the passive and active protection they require, but that these are fully and properly maintained throughout the life of the building. It is completely unreasonable to expect that fire fighters can lay hoses up staircases to floors more than 20 metres above the ground and still effectively fight a fire. It is even less reasonable to suppose that the fire can be fought from aerial ladders or platforms pitched from the street or adjoining property. Reliance on any other form of access, such as helicopters to deposit fire crews on the roof of a high rise structure (sometimes encountered in the planning proposals in some developing countries) or to perform rescues is not a viable concept and should not be included in any code. As Sir Eyre Massey Shaw wrote a hundred and fifty years ago –

“To be effective a fire fighter must enter buildings …”

Patently, we cannot expect fire fighters to enter buildings if there is little or no chance of successfully reaching the fire area while it is possible to deal with it, nor can we expect them to enter a building on the point of failure. Having entered it they must be able to operate in relative safety as they approach the fire compartment and then enter it to deal with the fire. They can only do so if the structure has been designed to permit not only escape of the occupants, but the access for fire fighters to deal with the problem. In high rise structures this means that they must have a protected route to reach the fire floor, the fire itself should be controlled and prevented from spreading unchecked until they can reach it, and the structure should be able to stand up to the attack from the fire for long enough for the fire fighters to reach the building and launch their attack on the fire. That can only be achieved if the building is equipped with: -

• Adequate means of escape and access for fire fighting,
• Protected shafts to allow fire fighters access to the fire without exposure to smoke, heat or flames,
• A fire detection and alarm system capable of giving early warning of a fire,
• Active protection systems such as sprinklers capable of containing the fire in the compartment of origin, and
• Risers and landing valves capable of supplying sufficient water and water pressure for the operation of the fire fighting equipment.

Where a smoke control system is fitted this should be designed to complement the other systems and should not be a “replacement” for any other active fire protection system. All too often the provision of one or other “life safety” system is used as an excuse to “trade off” something which is essential for the safety of the fire fighters or for the containment and extinction of a fire once started. Particularly in High Rise structures such “trade offs” should be approached with a great deal of caution and should only form part of any “approval” if it can be proved that the systems provided give the same, or a greater, level of protection without the “trade off”.

Equally important is the need to recognise that a building’s fire risk changes almost daily as the fire load is changed by alterations, by refurbishment and by the introduction of new plant and equipment. The built environment is dynamic, the fire risk is never static and it is therefore essential that designers, regulators and enforcers recognise that there is an unbreakable link between life safety of the occupants, property protection and the safety of fire fighters committed to deal with fire, evacuation or any other emergency. The fire protection must be built into these structures; it is not a luxury or something that can be fitted and forgotten. It is vital to the safe operation of any high rise building.

Finally, the entire solution needs to be understood and effectively managed throughout the life of the building. All to often the safety of both the occupants and of fire fighters is seriously compromised by building owners failing to maintain systems or attempting to save money by replacing parts or carrying out alterations which compromise performance. Without this final check – there is no safety in a High Rise structure.

Bibliography

Physiological Assessment of Firefighting, Search and Rescue in the Built Environment; December 2004, Optimal Performance Limited for the Office of the Deputy Prime Minister

Hydraulic Calculation of Wet and Dry Risers, Hoses and Branches; December 2004, BRE for the Office of the Deputy Prime Minister

Effect of Reduced Pressures on performance of firefighting branches in tall buildings – Aspects of High Rise Firefighting: Hunt S and Roberts G, December 2004 Office of the Deputy Prime Minister.

Collection and Analysis of Emergency Services Data Relating to the Evacuation of the World Trade Centre Towers of 11 September 2001; December 2004, Prof E R Galea and Mr J P Dixon, University of Greenwich for the Office of the Deputy Prime Minister.

IRMP Guidance Note 4; March 2004, Office of the Deputy Prime Minister, HM Inspectorate of Fire Services

Fire and Rescue Services Circular No 55/2004 – The Building Disaster Assessment Group – Key Research Findings; 2004; Office of the Deputy Prime Minister, HM Fire Service Inspectorate

NFPA Reports

Joelma Building, Sao Paolo, Brazil

MGM Grand Hotel, Las Vegas, USA

Standards

BS/EN 12845 – Fixed firefighting systems, Automatic Sprinkler Systems
NFPA 13 and related Codes.
NFPA 101 – Life Safety Code
Approved Document B – Issued as an adjunct to the National Building Regulations (UK)

Acknowledgement

My thanks go to Simon Hunt B Eng, of the Fire and Rescue Service Development Division and to John Fay BA (Hons) of the Fire Research and Statistics Division for their help and advice in preparing this paper.