nfpa - fundamentals of fire safe building design

~ ~ ~~

S T D * N F P A F P H S E C T I O N 1-2-ENGL bLI7LILILIb 0551ib3LI 737

Section K h a p t e r 2

FUNDAMENTALS OF FIRE SAFE BUILDING DESIGN

Revised by Robert Tì? Fitzgerald

Building design and construction practices have changed significantly during the past century. A little over one hundred years ago, structural steel was unknown, reinforced concrete had not been used in structural framing applications, and the first “high-rise” building had just been built in the United States.

The design professions have also advanced significantly during the past century. The practice of architecture has changed mark- edly, and techniques of analysis and design that were unknown a century or even a generation ago are available to engineers today. Building design has become a very complex process, with many skills, products, and technologies integrated into its system.

Fire protection has made developmental strides in the building industry similar to those of other professional disciplines. At the turn of the century, conflagrations were a common occurrence in cities. In later years, increased knowledge of fire behavior and building design enabled buildings to be constructed in such a manner that a hostile fire could be confined to the building of origin rather than to the block or larger areas. Progress has continued in the field of fire protection so that, at the present time, knowledge is available that enables a hostile fire to be confined to the room of origin or even to smaller spatial subdivisions in a structure.

DESIGN AND FIRE SAFETY Much activity is taking place today regarding fire safe building design. The general thrust of some developments appears to be direct- ed toward quantification procedures and identification of a rational design methodology to parallel or supplement the traditional “go or no go” specifications approach. Knowledge in the field of fire protection is undergoing development and reorganization that will enable buildings to be designed for fire safety more rationally and efficiently. This section of the Handbook identifies the components of a field that is changing dynamically in its analysis and design ca- pabilities.

“America Burning,” the report of the National Commission on Fire Prevention and Control,’ identifies several areas in which building designers create unnecessary hazards, often unwittingly, for the building occupants. In some cases, these unnecessary hazards are the result of oversight or insufficient understanding of the interpretations of test results. In other cases, they are due to a lack

Robert W. Fitzgerald, Ph.D., P.E., is professor of fire protection engineering and civil engineering at Worcester Polytechnic Institute, Worcester, MA.

of knowledge of fire safety standards or failure to synthesize an integrated fire safety program.

The Commission’s report cites that conscious incorporation of fire safety into buildings too frequently is given minimal attention by the designer and, further, that building designers and their clients are often content only to meet the minimum safety standards of the local building code. Frequently, both assume incorrectly that the codes provide completely adequate measures rather than minimal ones, as is the case. In other instances, building owners and occupants see fire as something that will never happen to them, as a risk that they will tolerate because fire safety measures can be costly, or as a risk adequately balanced by the provisions of fire insurance or availability of public fire protection.

Conditions arising from these attitudes need not exist, much less continue. Information is available for design professionals to incorporate a greater measure of fire protection into their designs. Use of fire protection information requires that the various members of the building design team recognize that fire conditions are a le- gitimate element of their design responsibilities. This requires a greater understanding of the special loadings that fire causes on building features and of the countermeasures that can be incorporated into designs.

The material in this chapter identifies the components of a complete fire safety system. The organizational structure may be used as a basis with which to evaluate the relative safety both of new designs and also of existing buildings.

Evaluating a design for building fire safety represents a systematic approach to the six principal types of fire safety strategies identified in Section 1, Chapter 1, “America’s Fire Problem and Fire Protection,” i.e., prevention, slowing of initial growth and spread, detection, suppression, compartmentation, and evacuation, in the context of the choices that canbe built into or installed in a building. This chapter describes in general terms the processes required to create such a design. More specific guidance requires joining the general processes described here with the more detailed guidance in later chapters on the specific fire safety strategies. Also, this chapter addresses an additional building strategy: designing the building to facilitate fire department operations should these become necessary.

’

Objectives of Fire Safe Design The conscious, integrated process of design for building fire safety, if it is to be effective and economical, must be integrated into the complete architectural process. All members of the traditional

1-26

Copyright National Fire Protection Association Provided by IHS under license with NFPA

Not for ResaleNo reproduction or networking permitted without license from IHS

--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^

^#^~

^^""

~:@

":^*^

~$~"

#:*~

~:""

"^^$

~~~#

^~:^

:@:~

*:$"

\\

S’TD-NFPA FPH S E C T I O N 1-2-ENGL b Y 7 Y Y Y b 0551b35 b 7 5 W

FUNDAMENTALS OF FIRE SAFE BUILDING DESIGN 1-27

building design team should incorporate, as an integral part of their work, design for emergency fire conditions. The earlier in the design process that fire safety objectives are established, alternative methods of accomplishing those objectives are identified, and engineering design decisions are made, the more effective and economical the final results.

As the first step in the process, setting objectives is part of clearly identifying the specific needs of the client with regard to the function of the building. After the building functions and client needs are understood, the designer must consciously ascertain both the general and the unique conditions that influence the level of fire risk that can be tolerated in the building. The acceptable levels of risk and the focus of the fire safety analysis and design process are concentrated in the following three areas:

I . Life safety. 2. Property protection. 3. Continuity of building operations.

It is difficult to ascertain the level of risk that will be tolerated by the owner, occupants, and community. Often it is necessary to put a conscious effort into recognizing the sensitivity of the occupants, contents, and mission of the building as to the products of combustion. Consequently, fire safety criteria often are not identified in a clear, concise manner that enables the designer to provide appropriate protection for the realization of the design objectives. Unfortunately, it is impossible to provide more than general guidelines that must be considered in building design to assist in the identification of the fire safety objectives in this handbook. Specific objectives must be developed for each individual building.

Life safety: Adequate life safety design for a building is often related only to compliance with the requirements of local building regulations. This may or may not provide sufficient occupant protection, depending upon the particular building function and occupant activities.

The first step of life safety design is to identify the occupant characteristics of the building. What are the physical and mental ca- pabilities of the occupants? What are the range of their activities and locations during the 24-hour, seven-day-a-week periods? Are special considerations needed for certain periods of the day or week? In short, the designer must anticipate the special life safety needs of occupants during the entire period in which they inhabit the building.

The identification of life safety objectives is usually not difficult, but it does require a conscious effort. In addition, it requires an appreciation of the time and extent to which the products of combustion can move through the building. The interaction of the building response to the fire and the actions of its occupants during the fire emergency determines the level of risk that the building design poses.

Property protection: Specific items of property that have a high monetary or other value must be identified in order to protect them adequately in case of fire. In some cases, specially protected areas are needed. In other cases, a duplicate set of vital records in another location may be adequate. The establishment of the fire safety objectives should ascertain if the user of the building has property that requires special fire protection.

Continuity of building operations: The maintenance of opera- tional continuity after a fire is the third major design concern. The amount of “downtime” that can be tolerated before revenues begin to be seriously affected must be identified. Frequently, certain functions or locations are more essential to the continued operation of the building than others. It is important to recognize those areas particularly sensitive to building operations, so that adequate protec-

tion is provided for the vital business operations conducted in them. Often, these areas need special attention that is not required throughout the building.

In modem buildings, the value of the contents of a single room may be extremely high. This value may be due to the cost of equipment or records, or to the high cost of business interruption. The sensitivity of equipment and data to the effects of heat, smoke, gases, or water must be addressed. In any event, the designer should protect the specially sensitive rooms from products of a fire origi- nating either inside or outside of the room.

In addition to objectives relating to the people, property, and mission that is provided by the building under consideration, two additional types of objectives are useful for some occupancy functions. The first is design for the protection of neighbors. A recogni- tion of the potential effect of exposure fires may influence the design sufficiently to mitigate potential problems. The second con- siders the impact on the environment from problems such as runoff of chemicals housed in the building that dissolved in fire department water applications. Waterborne or airborne products of combustion produced in buildings that house certain chemicals can affect the environment significantly. Also consideration for the safety of fire- fighting personnel responding to a building fire should be taken into account.

ELEMENTS OF BUILDING FIRE SAFETY

Fire Prevention As noted earlier, the first opportunity to achieve fire safety in a building is through fire (ignition) prevention, which involves sepa- rating potential heat sources from potential fuels. Table I-2A lists

TABLE 1-2A. Fire Prevention Factors

1. Heat Sources a. Fixed equipment b. Portable equipment c. Torches and other tools d. Smoking materials and associated lighting implements e. Explosives f. Natural causes g. Exposure to other fires

a. Building materials b. Interior and exterior finishes c. Contents and furnishings d. Stored materials and supplies e. Trash, lint, and dust f. Combustible or flammable gases or liquids g. Volatile solids

a. Arson b. Misuse of heat source c. Misuse of ignitable material d. Mechanical or electrical failure e. Design, construction, or installation deficiency f . Error in operating equipment g. Natural causes h. Exposure

a. Housekeeping b. Security c. Education of occupants d. Control of fuel type, quantity, and distribution e. Control of heat energy sources

2. Forms and Types of Ignitable Materials

3. Factors that Bring Heat and Ignitable Material Together

4. Practices that Can Affect Prevention Success



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@

:~*:$"\\

~~~ ~ -~~ ~

STD-NFPA FPH SECTION 1-2-ENGL b47444b 0551b3b 5 0 1 W

1-28 BASICS OF FIRE AND FIRE SCIENCE

common factors in fire prevention and identifies major candidate heat sources and ignitable materials, common factors that bring them together, and practices that can affect the success of prevention.

Most building fires are started by heat sources and ignitable materials that are brought into the building, not built into it. This means the design of the building, from the architect’s and builder’s standpoint, provides limited potential leverage on the building’s fu- ture fire experience. The building’s owners, managers, and occu- papts, however, will have numerous opportunities to reduce fire risks through prevention, and they should be urged to do so.

For design purposes, fire prevention will be enhanced by careful observance of codes and standards in the design and installation of the electrical and lighting system, the heating system, and any other major built-in equipment, such as cooking, refrigeration, air conditioning, and clothes washing and drying. Venting systems need to be designed carefully to carry carbon monoxide and potential fuels along protected paths. These venting systems will need to be inspected and cleaned regularly.

Protection from lightning and exposure fires will affect the external design of the building, particularly in certain parts of the country, such as areas near wildlands. A fire in one building creates an external fire hazard to neighboring structures by exposing them to heat by radiation, and possibly by convective currents, as well as to the danger of flying brands of the fire. Any or all of these sources of heat transfer may be sufficient to ignite the exposed structure or its contents.

When considering protection from exposure fires, there are two basic types of conditions: (1) exposure to horizontal radiation, and (2) exposure to flames issuing from the roof or top of a burning building in cases where the exposed building is higher than the buming building. Radiation exposure can result from an interior fire where the radiation passes through windows and other openings of the exterior wall. It can also result from the flames issuing from the windows of the burning building or from flames of the burning fa- cade itself. A source for guidelines and data on exposure protection is given in NFPA 8OA, Recommended Practice for Protection of Buildingsfram Exterior Fire Exposures.

inside the building, design features may make incendiarism, arson, or other human-caused fires more or less likely by making security and housekeeping easier or harder to perform. The interaction of the design with these critical support activities should be thought through and planned into the design from the outset.

Spread of Fire and Products of Combustion The concern here is with slowing the fire to provide other fire safety measures with sufficient time to be effective. A systematic design for this purpose should address the possible ways that hazard can grow rapidly, e.g., flame spread, rapid growth in rate of heat release or rate of mass release, unusually toxic gases, unusual corrosivity, quantity of fuel available to feed the fire, and so forth. Each of these can be evaluated separately in terms of the threat to exposed people, property, and mission of the building. The building design should provide effective countermeasures.

In a building fire, the most common hazard to humans is from smoke and toxic gases. Most building-related fire deaths are directly related to these products of combustion.. Death often results from oxygen deprivation in the bloodstream, caused by the replacement of oxygen in the blood hemoglobin by carbon monoxide. In addition to the danger of carbon monoxide, many other toxic gases that are present in building fires cause a wide range of symptoms, such as headaches, nausea, fatigue, difficult respiration, confusion, and impaired mental functioning.

Smoke, in addition to accompanying toxic and imtant gases, contributes indirectly to a number of deaths. Dense smoke obscures visibility and irritates the eyes and can cause anxiety and emotional shock to building occupants. Consequently, the occupant may not be able to identify escape routes and utilize them. (For more information, see Section 4, Chapter 2, “Combustion Products and Their Effects on Life Safety.”)

Although heat injuries do not compare in quantity to those caused by inhalation of smoke and toxic gases, they are painful, serious, and cause shock to victims. In addition to deaths from thermal products of combustion, the pain and disfigurement caused by non- fatal burns can result in serious, long-term complications.

Property also is affected by the thermal and nonthermal products of combustion, as well as by extinguishing agents. Smoke may damage goods located long distances from the effects of the heat and flames. Fires that are not extinguished quickly often result in considerable water damage to the contents and the structure, unless special measures are incorporated to prevent that damage. It should be noted, however, that the water damage caused in extinguishing a fire rarely exceeds the fire damage resulting from a fire that is not suppressed.

Fast flame spread over finish materials or building contents and vertical propagation of fire are serious concerns. The ability of the fire service to contain or extinguish a fire is diminished significantly if the fire spreads vertically to two or more floors. With a given potential for fire growth, the prevention of vertical fire spread is influenced principally by architectural and structural decisions involving details of compartmentation, which are discussed later.

Designing Countermeasures to Fire Growth The building fire safety system can be organized around the fire growth and its resulting products of combustion, i.e., flameheat and smokelgas. The ease of generation and movement of these products is influenced by the countermeasures provided by the building. The effectiveness of the building fire safety systems determines the speed, quantity, and paths of movement of these products of combustion.

The speed and certainty of fire growth and development in rooms can vary greatly. The contents and interior finish in some rooms are quite safe, and, for this type of situation, it is unlikely that, once ignited, a fire can grow to full involvement of the room. On the other hand, the interior design of other rooms poses a high hazard which, if an ignition were to occur, could lead to an almost certain full room involvement.

The traditional method of describing the fire growth hazard has been through fire loads reflected in use and occupancy classifica- tions. Building types, rather than rooms within buildings, have been grouped with regard to their relative hazard. For example, residen- tial and educational occupancies are considered low hazard, because they normally contain relatively low fuel loads in the rooms. Mercantile buildings are normally a moderate hazard, while certain industrial and storage buildings may be considered a high hazard because they contain a high fuel load.

This type of classification is a basis for building and fire code requirements, and, historically, it has been quite useful. However, a more detailed look at the fire growth potential within the rooms of a building can be a valuable part of a detailed fire safety design. The fire growth hazard potential, which identifies the speed and relative likelihood of a fire reaching full room involvement, is a useful base from which to design suppression interventions and to evaluate life safety problems. For example, situations where fast, severe fires will occur may call for automatic sprinkler protection, even though it may not be required by a building or fire code.



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@:~*:$"\\

STD-NFPA FPH SECTION 1-2-ENGL m b47LI44b 0551b37 4LIô


The basis for a fire growth hazard analysis is the combustion characteristics in a room. The main factors that influence the likelihood and speed with which full room involvement occurs are: (i) fuel load (Le., the quantity, type of materials, and their distribution); (2 ) interior finish of the room; (3) air supply; and (4) size, shape, and construction of the room.

Fire development in a room is neither uniform nor a guaran- teed progression from ignition to full room involvement. Fires develop through several stages, called realms. Table l-2B provides guidance on descriptions of the realms. Within any realm a tire may continue to grow or it may be unable to sustain continued development and die down. Table 1-2B includes a rough guide to the approximate flame sizes that may be used to describe the fire size of the realms. It also describes the major factors that influence growth within a realm. Absence of a significant number of the factors would indicate that the fire would self-terminate, rather than continue to develop.

TABLE 1-26. Major Factors Influencing Fire Growth

Approximate Ranges of Fire Major Factors that

Realm Sizes Influence Growth

1 Overheat to (Preburning) ignition.

2 Ignition to (Initial Burning) radiation point.

[lo in. (254 mm) high flame].

3 Radiation point (Vigorous to enclosure Burning) point [lo in. to

5 ft high flame (254 mm to 1.5 m)].

4 Enclosure point (Interactive to ceiling point [5 Burning) fî. (1.5 m) high

flame to flame touching ceiling].

5 Ceiling point to (Remote Burning) full room involve-

ment.

Amount and duration of heat flux. Surface area receiving heat material ignitability. Fuel continuity. Material ignitability. Thickness. Surface roughness. Thermal inertia of the fuel. Interior finish. Fuel continuity. Feedback. Material ignitability. Thermal inertia of the fuel. Proximity of flames to walls. Interior finish. Fuel arrangement. Feedback. Height of fuels. Proximity of flames to walls. Ceiling height. Room insulation. Size and location of openings. HVAC operation. Fuel arrangement. Ceiling height. LengtWwidth ratio. Room insulation. Size and location of openings. HVAC operations.

Different rooms pose different levels of risk regarding the likelihood of reaching full room involvement and the time in which fire development takes place. The factors in Table 1 -2B provide a general guide to the important types of factors.

If one were to focus on a single event that might be used to represent the relative level of risk posed by the contents and interior finish in a room, it would be the ability of flames to reach the ceiling. The arrangement of contents and types of fuels where it would be difficult for a fire to grow to touch the ceiling pose a relatively low fire growth hazard potential. On the other hand, where furniture combustibility and density will allow a fire to develop to ceiling

height, or when combustible interior finish is present, the fire growth hazard potential usually is comparatively high.

Detection and Alarm Fire detection provisions are needed so that automatic or manual fire suppression will be initiated, any other active fire protection systems will be activated (e.g., automatic fire doors for compartmentation and protection of escape routes), and occupants will have time to move to safe locations, typically outside the building.

One reason for concern over any rapid initiai fire growth is that it can shrink the time available after detection for these life- and property-saving responses. Therefore, detection provisions must he designed systematically to reflect the building’s other features, its occupants, and its other fire safety features.

For example, smoke is often the first indicator of tire, so a system of automatic detection based on smoke detectors often makes sense. In certain properties or areas, however, detectors based on heat or rate of increase in heat may be more appropriate because of the types of fires likely to occur in those areas or because of the potential for non-fire activations in those areas. Whatever type of detection system is chosen, it is important that. for each area of the building, a realistic assessment be made of the implications for response time after the fire is detected and before a lethal or other high-hazard condition develops.

Alarm provisions need not be linked to the detection sensor locations, but should be designed systematically to tell occupants what they need to do, based on where they are and their ability to respond. This would include the possible use of central annunciator panels and monitors to inform responsible staff, voice messages to provide instructions on occupant movements, and direct remote alarms to supervised stations or fire departments. All of these op- tions will have an impact on the time available for some type of response and, possibly, on the efficiency of that response. A timeline can he constructed to provide a quantitative base for analysis and design of this and related building fire safety features.

Automatic Suppression For nearly a century and a half, automatic sprinklers have been the most important single system for automatic control of hostile fires in buildings. Many desirable aesthetic and functional features of buildings that might offer some concern for fire safety because of the fire growth hazard potential can he protected by the installation of a properly designed sprinkler system.

Among the advantages of automatic sprinklers is the fact that they operate directly over a fire and are not affected by smoke, toxic gases, and reduced visibility. In addition, much less water is used because only those sprinklers fused by the heat of the fire operate, particularly if the building is compartmented.

Other automatic extinguishing systems, e.g., carbon dioxide, dry chemical, clean (halon replacement) agents, and high-expan- sion foam, may be used to provide protection for certain portions of buildings or types of occupancies for which they are particularly suited.

An automatic sprinkler system has been the most widely used method of automatically controlling a fire. The major elements for determining the effectiveness of an automatic sprinkler system are: ( 1 ) its presence or absence; (2) if present, its reliability; and (3) if reliable, its design and extinguishing effectiveness.

Although automatic sprinkler systems have a remarkable record of success, it is possible for the system to fail. Often failure is due to a feature that could have been avoided if appropriate attention had been given at the time of the system’s design, installation,



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@:~*:$"\\

STDONFPA FPH S E C T I O N 1-2-ENGL b47444b 0551638 384 D


or maintenance. Table 1-2C describes common failure modes and their causes. During the design stages, these factors should be addressed to increase the probability of successful extinguishment by the sprinkler system.

TABLE 1-2C. Common Automatic Sprinkler Failure Modes

Failure Mode Potential Causes

Water supply valves are closed when sprinkler fuses. Water does not reach sprinkler.

Nozzle fails to open when expected.

Water cannot contact fuel. (Note: The intent of this failure mode is to ensure that discharge is not interrupted in a manner that will prevent fire control by a sprinkler.)

Water discharge density is not sufficient.

Enough water does not continue to flow.

Inadequate valve supervision. Owner attitude. Maintenance policies. Dry pipe accelerator or exhauster

Pre-action system malfunctions. Maintenance and inspection

Fire rate of growth too fast. Response time and/or temperature

of link inappropriate for the area protected.

Sprinkler link protected from heat. Sprinkler link painted, taped,

Sprinkler skipping. Fuel is protected. High-piled storage is present. New construction (walls, ductwork,

ceilings) obstructs water spray.

malfunctions.

inadequate.

bagged, or corroded.

Discharge needs are insufficient for the type of fire and the rate of heat release.

Change in combustible contents occurred.

Number of sprinklers open is too great for the water supply.

Water pressure is too low. Water droplet size is inappropriate

for the fire size. Water supply is inadequate because

of original deficiencies, changes in water supply, or changes in the combustible contents.

Pumps are inadequate or unreliable. Power supply maifunctions. System is disrupted.

Compartmentation Barriers, such as walls, partitions, and floors, separate building spaces. These barriers also delay or prevent fire from propagating from one space to another. In addition, barriers are important features in any fire-fighting operation.

The effectiveness of a barrier is dependent upon its inherent fire resistance, the details of construction, and the penetrations, such as doors, windows, ducts, pipe chases, electrical raceways, and grilles. Although the hourly ratings of fire endurance do not always represent the actual time that the barrier can withstand a building fire, unpenetrated rated barriers seem to perform rather well. This may be due to the rather large factor of safety inherent in the codes. On the other hand, it is quite common for rated barriers to fail because of inattention to penetrations. For example, the fire resistance of a rated floor-ceiling assembly can be voided because of large or

numerous poke throughs. The fire resistance of a rated partition is lost when a door is left open.

Fire resistance requirements imposed by the regulatory system often have comparatively little meaning because of inattention to the functional and construction details. To predict field performance of barriers, the penetrations and details of construction must be considered, in addition to the fire endurance of the base construction.

The major function of barriers is to prevent heat and flame spread from causing an ignition in an adjacent room or floor. It is useful to classify barrier failure in two categories. One is a massive bamer failure, which would occur when a part of the barrier col- lapses or when a large penetration, such as a door or a large window, is open. When a massive failure occurs, the adjacent room can become fully involved in a short period of time. The second type of failure is a localized penetration failure. This occurs when flames or heat penetrates small poke throughs or small windows. A localized penetration failure causes a hot spot to occur. If fuel is present and ignition occurs, this could lead to a full room involvement by the normal fire development progression.

Smoke and gases move through a building much faster and more easily than flames and heat. The time duration from ignition until a building space is untenable is an important aspect of fire safety, and the loss of tenability may be due to smoke and gases more often than flames and heat. Therefore, barriers need to be designed and considered as barriers to the spread of smoke and fire gases, too.

In addition to its value as means of containing the fire, compartmentation also addresses specific needs for protection, such as structural integrity of the building and escape routes.

The collapse of structural building elements can be a serious life safety hazard. Although statistically it has not resulted in many deaths or injuries to building occupants, structural collapse is a particular hazard to fire fighters. A number of deaths and serious injuries to fire fighters occur each year because of structural failure. While some of these failures result from inherent structural weak- nesses, many are the result of renovations to existing buildings that materially, though not obviously, affect the structural integrity of the support elements. A building should not contain surprises of this type for fire fighters.

The potential for structural collapse must be determined. Building codes address this aspect through construction classification requirements. The relationship between fire severitg and fire resistance to collapse are the principal factors.

Collapse can occur when the fire severity exceeds the fire endurance of the structural frame. However, this is comparatively rare. Structurai collapse is more commonly associated with deficiencies in construction. These deficiencies are not evident under normal, everyday use of the building. They become a problem when the fire weakens supporting members, triggering a progressive collapse.

Design for Evacuation and Occupant Movement The design for life safety may involve one or a combination of the following three alternatives: (1) evacuation of the occupants, (2 ) defending the occupants in place, or (3) providing an effective area of refuge. These alternatives can be evaluated by the likelihood that the building spaces will be tenable for the period of time necessary to achieve the expected level of safety. The criteria for tenability, therefore, becomes an important part of the design.

Evacuation: The design for building evacuation involves two major components: (1) the availability of an acceptable path or paths for escape, and (2 ) the effective alerting of the occupants in suffi-



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@

:~*:$"\\

STDeN FPA FPH S E C T I O N 1-2-ENGL = b47444b 0552b39 220 FUNDAMENTALS OF FIRE SAFE BUILDING DESIGN 1-3 1

cient time to allow egress before segments of the path of egress become untenable.

Alerting occupants to the existence of a fire is a vital part of the life safety design. A useful performance objective could be to identify that occupants should have at least x minutes to escape from the time they know of a fire until the escape route is blocked. To accom- plish this, the designer either must ensure that the fire and the movement of its products of combustion will be slow enough to provide that time, or incorporate special provisions into the building to achieve that objective.

Defending in place: The second life safety design alternative is to defend the individual in place. This may be appropriate for occupancies such as hospitals, nursing homes, prisons, and other institu- tions. It may be an appropriate alternative for other buildings when the size or design may show that evacuation has an unacceptably low likelihood of success. Defend-in-place design also uses a performance criteria of time and tenability levels.

The performance criteria relating to time might state that the building space should be tenable for y minutes after the stari of the fire. The duration for y could be identified as a period much longer than the duration of any possible fire. The definition of tenability may be quite different from that acceptable for evacuation because of the influence of both time and the products of combustion.

Refuge: The third alternative is to design for an area of refuge. This involves occupant movement through the building to specially designed refuge spaces. This type of design is more difficult than either of the other two alternatives because it involves the major design aspects of each. In certain types of buildings this may be a reasonable altemative. However, an evaluation of the effectiveness of the area of refuge design and its likelihood of success are extremely important.

Life safety design for a building is difficult. It involves more than a provision for emergency egress. It must also address the pop- ulation who will be using the building and what they will be doing most of the time. Consideration must then be given to communication, the protection of escape routes, and temporary or permanent areas of refuge for a reasonable period of time for the building occupants to achieve safety.

Even occupants familiar with their surroundings often experience difficulty in locating means of egress. The problem is com- pounded for transients and occasional visitors to the building. Architectural layout and normal circulation patterns are important elements in emergency evacuation. For example, many large office buildings are a maze of offices, storage areas, and meeting rooms. Clearly marked emergency travel routes can enhance life safety features in all buildings.

Design for Fire Department Operations The protection offered by a community fire department has an important influence on building fire design. Some buildings are designed in a manner that helps the fire department extinguish fires while they are small; others are designed in a manner that hinders a fire department. Rarely does the designer consciously design the building for emergency operations. The following discussion provides some guidelines for building design to enhance the building’s ability to allow the fire department to extinguish a fire with minimal threat to life and property.

Ideally, a building is designed so that should a fire occur, it can be attacked before it extends beyond the room of origin. If that is not possible, the building design and construction features should retard fire spread so that the fire department will encounter a relatively

small, easily controllable fire. The major aspects of this part of building design include: (1) fire department notification, ( 2 ) initial agent application, (3) fire extinguishment, (4) ventilation, (5) water supply and use, (6) water removal, and (7) barrier effectiveness. These aspects are discussed briefly to provide guidance for incorpo- rating features into the building that enable departments to be more effective and less harmful to the building.

Fire department notification: The complete chain of events, Le., (1) detection of the fire, (2) decision to inform the fire department, (3) sending of the message, and (4) correct receipt of the information by the fire department, should be a part of every building fire safety design. It should be consciously designed, rather than left to chance. The time durations for completing the events through agent application are very dependent upon the speed of the fire spread. Buildings have been lost because of insufficient attention to the method of notifying the local fire department.

Agent application: The next critical event is fire department application of agent to the fire. This involves three distinct events for its success: (1) amval at the site, ( 2 ) nozzle entrance into the room, and (3) water discharge from the nozzle. Each of these events can be affected by site or building access considerations in the design.

Ideal exterior accessibility occurs where a building can be ap- proached from all sides by fire department apparatus. This is not always possible. In congested areas, only the sides of buildings facing streets may be accessible. In other areas, topography or constructed obstacles can prevent effective use of apparatus in combating the fire.

Some buildings located some distance from the street make the approach of apparatus difficult. If obstructions or topography prevent apparatus from being located close enough to the building for effective use, fire-fighting equipment, e.g., aerial ladders, elevating platforms, and water tower apparatus, are rendered useless. Valu- able labor must be expended to hand carry hose lines or ground ladders long distances.

The matter of access to buildings has become far more compli- cated in recent years especially in light of the movement to secure buildings against possible terrorist attacks. The building designer must consider this important aspect in the planning stage. Inade- quate attention to site details can place the building in an unneces- sarily vulnerable position. If its fire defenses are compromised by preventing adequate fire department access, the building must compensate with more complete internal building protection.

The arrival at the site is only a part of the agent application evaluation. The fire fighters then must be able to enter the building, reach the floor of the fire, and find the involved room or rooms. This is often a time-consuming, difficult task. Considerable attention must be given to the problem of finding the fire and getting fire fighters and equipment to the fire.

Access to the interior of a building can be greatly hampered where large areas exist and where buildings have blank walls, false facades, solar screens, or signs covering a high percentage of exterior walls. Obstacles that prevent ventilation allow smoke to accu- mulate and obscure fire fighters’ vision. Lack of adequate interior access also can delay or prevent fire department rescue of trapped occupants.

Windowless buildings and basement areas present unique fire- fighting problems. The lack of natural ventilation facilities, such as windows, contributes to the buildup of dense smoke and intense heat, which hamper fire-fighting operations, Fire fighters must at- tack fires in these spaces despite heat and smoke. This can result in lengthy times for fire extinguishment and greater damage by the products of combustion.



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@

:~*:$"\\

~ ~~ ~~~ ~ ~

STD-NFPA FPH SECTION 1-2-ENGL b47‘4‘4’4b 0 5 5 L b 4 0 T32


Fire extinguishment: After the time-consuming and sequential events of notification and initial agent application have transpired, the fire department is ready to fight the fire. The size of fire that is present at the time of initial agent application determines the fire- fighting strategy and likelihood of success of the operation.

Broadly speaking, three categories of fire conditions may be expected: (1) comparatively small fires may be extinguished by direct application of water; (2) when the fire is larger than can be directly extinguished, the building is opened (ventilated), and the hose streams drive the fire, heat, and smoke out of the building; and (3) fires that are too large for this operation must be surrounded. All available techniques of ventilation and heat absorption by water evaporation are used; however, the fire area is lost, and the main purpose of this strategy is to protect exposures, both external and internal.

Ventilation: Ventilation is an important fire-fighting operation. It involves the removal of smoke, gases, and heat from building spaces. Ventilation of building spaces perfoms the following important functions:

Protection of life by removing or diverting toxic gases and smoke from locations where building occupants must find temporary refuge. Improvement of the environment in the vicinity of the fire by removal of smoke and heat. This enables fire fighters to advance close to the fire to extinguish it. Control of the spread or direction of fire by setting up air currents that cause the fire to move in a desired direction. In this way, occupants or valuable property can be more readily protected. Provision of release for unburned, combustible gases before they develop a flammable mixture, thus avoiding a backdraft or smoke explosion.

The building designer should be conscious of these important functions of fire ventilation and provide effective means of facilitat- ing venting practices whenever possible. This may involve access panels, movable windows, skylights, or other means of readily opened spaces in case of a fire emergency. Emergency controls on the mechanical equipment or inclusion of an engineered smoke- control system may also be an effective means of accomplishing the functions of fire ventilation. Each building has unique features, and, consequently, a unique solution should be incorporated into the design.

Water supply and use: Water is the principal agent used to extinguish building fires. Although other agents may be employed occa- sionally (e.g., carbon dioxide, dry chemical, foams and surfactants, and clean halon replacement agents), water remains the primary extinguishing agent of the fire service. Consequently, the building designer should anticipate the needs of both the fire department and automatic extinguishing systems and provide an adequate supply of water at adequate residual pressure.

Water normally is supplied to the building site by mains that are part of the water distribution system. Few cities can supply a sufficient amount of water at required pressures to every part of the city Consequently, water supplied to hydrants, standpipes, or sprinklers must be boosted by pumps located on fire department apparatus or in the buildings themselves. Buildings that do not have an adequate, reliable water source for fire fighting must either provide supplemental water or incorporate other fire defense measures to compensate for this deficiency.

Careful attention must be given to water supply, distribution, and pressure for emergency fire conditions. High-rise buildings are

particularly sensitive in this respect because the water pressures that are required depend upon building height. The water supply needs of large buildings must also be given careful attention.

Fire conditions that require operation of a large number of sprinklers or use of a large number of hose streams can reduce pressure in standpipe and sprinkler systems to the point where residual pressures in the distribution system are adversely affected. Fire department connections for sprinkler and standpipe systems are important components of building fire defenses. The building designer must carefully consider installation details of fire department connections to make sure they will be easily located, readily accessible, and properly marked. Locations should be approved by the local fire department.

Water remsval: Watertight floors are important in this respect. Salvage efforts can be greatly affected by the integrity of the floors. Of greater importance is the number and location of floor drains. If interior drains and scuppers are available, salvage teams can effec- tively remove water with a minimum of damage to the structure.

BIBLIOGRAPHY

Reference Cited

1. NCFPC, “America Burning,” the report of the National Commission on Fire Prevention and Control, 1973, Superintendent of Documents, U.S. Government Printing Office, Washington, DC.

NFPA Codes, Standards, and Recommended Practices

Reference to the following NFPA codes, standards, and recommended practices will provide further information on the fundamentais of fire safe building design discussed in this chapter. (See the latest version of The NFPA Catalog for availability of current editions of the following documents.)

NFPA 13, Standard for the Installation of Sprinkler Systems NFPA 14, Standard for the Installation of Standpipe and Hose Systems NFF’A 22, Standard for Water Tmks for Private Fire Protection NFF’A 24, Standard for the Installation of Private Fire Service Mains and

NFPA 70, National Electrical Code@ NFPA 72, Natwnal Fire Alarm Code NFPA 80A, Recommended Practice for Protection of Buildings from Exte-

NFF’A 92A, Recommended Practice for Smoke-Control Systems NFF’A 92B, Guide for Smoke Management Systems in Malls, Atria, and

NFPA IOIB, Life Safety Code@ NFPA 232, Standard for the Protection of Recorús NFPA 241, Standard for Safeguarding Construction, Alteration, and Dem-

NFPA 263, Standard Method of Test for Heat and Visible Smoke Release

NFPA 264A, Standard Method of Test for Heat Release Rates for Uphol-

Their Appurtenances

rior Fire Exposures

Large Areas

olition Operations

Rates for Materials and Products

stered Furniture Components or Composites and Mattresses Using an Oxygen Consumption Calorimeter

Fighting NFPA 1231, Standard on Water Supplies for Suburban and Rural Fire

Additional Reading

Allen, W., “Fire and the Architect-the Communication Problem,” Fire Safety Journal, Vol. 14, No. 4, 1989, pp. 205-220.

Anchor, R. D., Malhotra, H. L., and Purkiss, J. A., eds., Proceedings of the international Conference on Design of Stmctures Against Fire, Elsevi- er, New York, 1986.

Barker, J. A., “Training: The Key to Fire Safety,” Fire Prevention, No. 224, NOV. 1989, pp. 28-30.



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@:~*:$"\\

STD*NFPA FPH SECTION L-2-ENGL b1171144b O55Lb4L 977


Beck, V. R., and Poon, S. L., “Results from a Cost-Effective Decision-Mak- ing Model for Building Fire Safety and Protection,” Fire Safety Jour- nal, Vol. 13, Nos. 2 & 3, 1988, pp. 197-210.

“Design Guide: Structural Fire Safety-CIBW14 Workshop Report,” Fire Safety Journal, Vol. 10, No. 2, 1986, pp. 75-138.

“Designing Effective Fire Protection,” Civil Engineering, JulylAugust 1988, p. 2.

Dunning, G., Firepruoj Fire-Resistant or Semi-Combustible Designing for Fire Safety in High-Rise Buildings: A Partially Annotated Bihliogra- phy, Vance Bibliographies, Monticello, IL, 1989.

Egan, M. D., Concepts in Building Firesafety, R. Krieger, Malabar, FL, 1986.

Fire Test Standards, 2nd ed., American Society for Testing and Materials, W. Conshohocken, PA, 1988.

Gilardi, S. A., “Planning for Fire Safety,” Construction SpeciJer, Vol. 41, No. 4, April 1988, pp. 33-34.

Clon, P. L., “Building Safety-A New Educational Approach,” Building Standards, Vol. 56, No. 2, 1987, pp. 20-21.

Harmathy, T. Z., “Properties of Building Materials,” SFPE Handbook uf Fire Protection Engineering, National Fire Protection Association, Quincy, MA, 1995.

The Institution of Engineers, Fire Safety Engineering for Building Structure and Safety, E. A. Books, Crows Nest, Australia, 1989.

Iwankiw, N., “Design Aids for Fire Protection,” ProceedingsSolutions in Steel, The National Engineering Conference, AISC, 1986, p. 23.

Koyamatcu, T. J., “Automatic Fire-Extinguishing Systems,” Building Stan- dards, Vol. 56, No. 3, 1987, pp. 5-8.

Ley, M., Grading Methods of Building Fire Safety, M. S . Thesis, Worcester Polytechnic Institute, Worcester, MA 1987.

Luck, H., er al., “New Technologies in Automatic Detection and Suppres- sion,” Proceedings of the Conference on New Technologies to Reduce Fire Losses and Costs, Elsevier, 1986, pp. 21 1-218.

Malhotra, H. L., Fire Safety in Buildings, Building Research Establishment, Borehamwood, England, 1987.

Morikawa, T., Yanai, E., and Nishina, T., “Evaluation of Toxic Gases from Experimental Fires in an Existing Building,” 9th Joint Panel Meeting of the UJNR Panel on Fire Research and Safety, NBSIR 88-3753,April 1988, National Bureau of Standards, Gaithersburg, MD, pp. 443454.

Moms, J., “Life Safety and Sprinkler Protection,”Fire Prevention, No. 209, May 1988, pp. 18-21.

Nakamura, H., “Investment Model of Fire Protection Equipment for Office Buildings,” Proceedings of the First International Symposium on Fire Safety Science, Hemisphere, Washington, DC, 1986, pp. 1019-1028.

Nelson, H. E., “An Engineering Fire Protection Design Assessment Sys- tem,” 9th Joint Panel Meeting of the UJNR Panel on Fire Research and Safety, NBSIR 88-3753, April 1988, National Bureau of Standards, Gaithersburg, MD, pp. 157-171.

Nelson, H. E., “Room Fires as a Design Determinate-Revisited,” Fire Technology,Vol. 26, No. 2, May 1990, pp. 99-105.

Nelson, H. E., and Walton, W. D., “Basic Structure of the Fire Protection Design Assessment System,” NBSIR 85-3298, Feb. 1986, National Bu-

. reau of Standards, Gaithersburg, MD. Ow, C. S., and Thin, C. C., “Upgrading Fire Protection in Existing Build-

ings,” Fire international, Vol. 12, No. 112, AugusVSeptember 1988, pp. 39-40.

Quintiere, J., “Analytical Methods for Firesafety Design,” Fire Technology,

Rogowski, B. F. W., “Investigating the Contribution to Fire Growth of Com- bustible Materials Used in Building Components,” Proceedings of the Conference on New Technology to Reduce Fire Losses and Costs, Elsevier, New York, 1986, pp. 88-105.

Vol. 24, NO. 4, 1988, pp. 333-352.

Shields, T. J., Buildings and Fire, Wiley, New York, 1987. Singh, J., and Thomas, P. M., “Calculating the Overall Fire Risk in New

Building Designs,” Fire Prevention, No. 224, Nov. 1989, pp. 32-36. Twilt, L., and Witteveen, J., “Trends in Fire Safety Design of Buildings,”

Heron, Vol. 32, No. 4, 1987, pp. 95-1 14. Vance, M., Fireproof Building: A Bibliography, Vance Bibliographies, Mon-

ticello, IL, 1988. Volkmann, P., “Three Leading Factors to Save Life and Property,” Fire In-

ternationa[, Vol. 12, No. 109, FebruarylMarch 1988, pp. 39-40. White, A. G., Fire Safety Workplace Security: A Selected Bibliography,

Vance Bibliographies, Monticeiio, IL, 1986. Yurkonis, P. R., “Evaluating the Fire Safety of an Existing Building,” Facil-

ities Management, Operation, and Engineering, Vol. 16, No. 2, 1989, p. 16.



--`,,```,,,,````-`-`,,`,,`,`,,`---

//^:^^#^~^^""~:@":^*^~$~"#:*~~:"""^^$~~~#^~:^:@

:~*:$"\\