Evaluation of Fire Safety free download -BookHSSE WORLD

Evaluation of Fire Safety is a comprehensive book that explores different aspects of fire safety, ranging from the nature of the fire hazard, major fire hazard areas, and the cost of fires to the prescriptive and functional approach to fire safety. The book discusses the fire safety system, including its objectives, design steps, and sources of fire safety data. It examines various subsystems such as fire occurrence and prevention, fire development and control, harmful effects, and fire safety design and management. The book also covers the contribution of fire safety engineering, approaches to quantitative evaluation of fire safety, and risk management.

Table of Contents

The nature of the fire hazard

The hazard of fire is the consequence of uncontrolled, exothermic chemical reactions, especially between organic materials and air. It is particularly associated with combustible materials and energy sources used by people in everyday life. Although fire threatens both life and property and its control occasions much expenditure, the hazard must be set against the benefit gained from these resources so that a balanced view can be obtained. Moreover, living standards are highly dependent on the use of buildings. The extra danger when fires occur in an enclosure, with the heat and smoke being trapped rather than moving relatively harmlessly upward, needs to be set against the intrinsic value of using buildings. It follows that one cannot, in general, eliminate fire hazards, although one can reduce it to an acceptably low level by suitable design procedures.

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Interaction between fire hazard and other hazards

Fire takes its place alongside many other hazards in living. These include health hazards such as epidemics and sickness, industrial transportation, and domestic accidents, as well as natural
hazards such as earthquakes, floods, hurricanes, and so on. The fire hazard can of course be reduced by a severe restriction on the use of energy and combustible materials, but this could bring in its wake suffering and cost in excess of any alleviation of the fire problem. It could even give rise to conditions that prompt other hazards, particularly health hazards. There is a tendency for people who specialize in fire safety to look at the fire problem in isolation. One must be careful not to lose perspective in so doing, for example, with regard to the benefits that might ensue from using a material or process that might incidentally impose an increased fire hazard.

This point is illustrated diagrammatically in Figure 1.1 (Rasbash, 1974). Risks are associated with the act of living. Some risks have to be taken, while others are taken voluntarily. Risks are taken to obtain a benefit, of which perhaps a notional measure might be denoted by A. Amongst the risks, there are those with fire, which may inflict a penalty of “detriment” of fire damage and hurt because of fire occurrence. These may be assigned a notional value of fd (“d” for detriment). The fire danger requires a fire safety program that inflicts a cost of fc (“c” for cost). In the same way, other hazard scenarios inflict detriment hd, and the safety program costs of hc. The object of any rational program toward controlling fire safety should be to maximize the total benefit: [A – (fd + fc) -(hd + hc)].

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**Figure 1.1. Fire safety in the community**

Two examples serve to illustrate this point. Insulation in houses saves energy and would thus increase A. Insulation, particularly on the inside surfaces of a room, is also known to increase the rate of fire spread even if the insulation is not combustible. The introduction of such insulation would therefore serve to increase fd. Would [A – fd] be increased by the introduction of insulation? Many effective insulating materials are in themselves highly flammable. This tends to rule out their use on interior walls. It is normal in these circumstances to introduce a noncombustible layer on the inside wall with extra cost fc. In this case, the relevant benefit is the change in the value of [A – (fd + fc)].

The provision of smoke-stop doors is common in buildings, particularly in the United Kingdom. These of course occasion a certain cost that contributes to fc. As long as they can be opened when necessary by people escaping a fire, such doors reduce the risk of death in the event of a fire and thus reduce fd. But an extra cost that tends not to be brought into the equation is the inconvenience of having these doors scattered about buildings, particularly for those who have a physical handicap. There is a consequent reduction of the general benefit factor A, although in this case, the reduction is difficult to quantify. This factor usually manifests itself by the doors being propped open much of the time, thus nullifying much of the reduction in fd. Again, this can be overcome by having such doors held open and closed only following the automatic detection of fire. This substantially increases the cost of fc.

Major fire hazard areas

Fires causing loss and damage can occur wherever human activity occurs. Perhaps the most frequent location for fires is within buildings. These include both domestic and non-domestic premises, and the latter can extend to a wide range of occupancy, such as factories of various kinds, buildings where there are special risks to the public, including places of public assembly, and places where people sleep, such as hotels and hospitals. Industrial occupancies extend beyond buildings to include mines, process plants housed in the open, offshore installations, agricultural crops, and forestry. Finally, there is a whole range of facilities for road, rail, marine, and air transport even extending in recent times to satellites and space modules. For most of these hazard areas, a considerable and costly fire occurrence background has built up over the years and has given rise to extensive requirements for fire safety. In the world of fire insurance, specific hazard areas are often called “risks.”

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