Annals of Burns and Fire Disasters - vol. XI - n. 4 - December 1998

METHODOLOGY OF RECORDING THE CAUSES OF FIRE DISASTERS

Saini K.N.

Fire Corps Headquarters of Greece, Direction of Technical Applications, Athens, Greece

SUMMARY. This paper considers the main theories, definitions and approaches in the methodology of recording the causes of fire disasters. Fire risk is analysed and fire prevention factors are listed. Methods of estimating and calculating fire risk are also considered. The question of acceptable risk and unavoidable risk is discussed. Fire prevention depends on accurate definitions of the risks involved and on the intentions of the fire prevention design plan.

Introduction

In the rapidly developing scientific field of fire studies, one of the most useful and unusual branches is that of fire risk analysis. This discipline provides a flexible approach for estimating the impact of any type of fire safety strategy in terms of actual reduction of losses (death, injury, damage) and in terms that can be compared on the basis of the cost of programmes and strategies.
The present study reports the main theories, definitions and approaches in the methodology of recording the causes of fire disasters.

Fire risk analysis: a measure or a probability

Fire risk analysis is still an open question. It is always in two steps:

1. measure of severity
2. probability distribution

The measure of severity may also be separated into two parts:

1. definition of the scale that measures severity, such as number of fatalities and injured persons, dollars' worth of damage, area affected by flames or smoke, etc.
2. definition of the rules for calculating the specific severity measurement to be used for a particular fire

The probability distribution provides the probability, for each value, that the severity measure may have, i.e., the probability for every type of fire.
As actual fires reflect all the factors that affect ignition probability and fire severity, fire risk analysis usually begins with the calculation of fire prevention factors.

Fire prevention factors

It is essential to understand that the major factors in fire prevention are the initial input in any fire risk analysis approach, in order to organize a fire security system which is always designed on the basis of the development of fire and its resulting combustion products, i.e., smoke and gas.
Table 1 lists the major factors in fire prevention. These concern the most important heat sources and flammable materials, the major factors that bring them together, and building practices that can affect the success of prevention.

Fires develop in several stages, or "realms". Table II provides guidance on the technical definition of these realms. Within any realm a fire may either continue to grow or be unable to sustain continued development and die down. Table II includes a rough guide to the approximate flame sizes that may be used to describe the size of the realms. It also describes the major factors that influence growth within a realm. Absence of a significant number of factors indicate that the fire will self-terminate rather than continue to develop.

Risk estimation and evaluation

A fire risk analysis designer must ascertain both the general and the particular conditions that influence the level of fire risk that can be tolerated in a given building or space.

• The acceptable levels of risk and the focus of fire safety analysis and strategy processes are concentrated under the following headings
• Safety
• property protection
• continuity of building or space operations

It is important, at this stage of the present analysis, to describe what is an acceptable risk.
Fire risk analysis may be distinguished as:

1. Risk estimation, i.e., the estimation and analysis of the measure of severity and probability and their associated uncertainties
2. Risk evaluation, i.e., the additional steps required to be decided regarding the importance of a particular value of risk or a change in risk

A fire analysis that includes risk evaluation may be called a fire risk assessment in order to underline the fact that the analysis will support value judgements.
Acceptable risk is the term used when the method of risk evaluation involves treating risk as a constraint. This method may seem attractive because it refuses to consider costs until or unless a sufficient degree of fire safety has been provided. In an acceptable risk approach, a certain level of risk is defined as acceptable, and all alternatives meeting that level are evaluated strictly on the basis of cost.
When acceptable risk is not defined in terms of affordable risk, it is often defined in the following terms:

• historically acceptable risk (i.e., "anything in use for a long time is all right"), which may be overturned if public understanding of the magnitude of the risk changes dramatically

• unavoidable risk, such as the use of background radiation levels as a guide for acceptable exposure to medical X-rays

The most extreme version of an acceptable risk approach is the minimum risk approach. It is difficult to ascertain the level of risk that will be tolerated by the owner of a building, its occupants, and the community. It is often necessary to make a conscious effort to arouse the sensitivity of the occupants to the contents and the purpose of the building (or the space it occupies), with regard to the products of combustion.
Consequently, fire safety criteria are often not identified in a clear, concise manner that enables the designer to provide appropriate protection for the realization of design objectives. It is unfortunately impossible to provide more than some general guidelines that must be considered in building design in order to assist in the identification of fire safety objectives. Specific objectives must be developed for each individual building or space.
Safety. The first step in safety fire risk analysis design is to identify the characteristic occupants of the building or the space (e.g., a stadium). What are the physical and mental capabilities of the occupants? What is the range of their activities and locations during the 24-hour, sevenday-a-week period? Are special considerations needed for certain periods of the day or week? The interaction of the building's response to the fire with the actions of its occupants during the fire emergency determines the acceptable 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.
Continuity of building operations. The third major design concern is the maintenance of operational continuity after a fire. The amount of "downtime" that can be tolerated before revenues begin to be seriously affected must be identified. Certain functions or locations are more essential for continued operation of the building than others. It is important to identify areas of the building that are particularly sensitive to space (or building) operations, so that adequate protection can be provided for the vital business operations that are conducted in them.

Conclusions

Before the concept of acceptable level of risk comes into play, there must be an initial structuring of the problem that describes the type of building, the characteristics of it soccupants, and the types of fires to be studied, as already seen in Tables I and II Probability distributions may be needed for any of the major.fire prevention factors presented in the Tables.
Even if only a single building is being analysed, the building's behaviour with respect to fire may vary as a function of randomly varying conditions, such as the position of doors and windows (open or closed) or of forced air heating and cooling systems (on or off).
Occupant location and conditions may also vary in random or patterned manner. The most important point to remember in defining types of fires is that all the possible manners of fire ignition must be covered. Fires may have to be grouped into classes that are not entirely homogeneous, but it is not sound practice to exclude certain categories of fire. At present fire risk analysis is capable of dealing with only a small fraction of these major fire prevention factors, but useful results are nevertheless possible.

RESUME. L'Auteur considère les théories principales, les définitions et les approches de la méthodologie de la description des désastres d*incendie. Le risque d'incendie est analysé et les facteurs pour la prévention listés. L'Auteur considère en outre les méthodes pour évaluer et calculer les risques de feu et discute la question du risqué acceptable et du risque inévitable. La prévention des incendies dépend de la précision des définitions des risques relatifs et des intentions de ceux qui rédigent les plans pour la prévention des incendies.

Acknowledgements: The author wishes to thank Dr B.A. Papavasilopoulos and colleagues at the Laboratory of Gas Turbines in the University of Patras for their cordial guidance and Commander A. Haralabakos and the technical staff in the Direction of Technical Applications in the Hellenic Fire Corps Headquarters for their help and continuous assistance.

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