DISASTER PREVENTION AND MITIGATION REVIEW REPORT
The Centre for Research on the Epidemiology of Disasters
(CRED) defines disaster as “a sudden situation or even that overwhelms the
local capacity, necessitating a request at the national or international level
for external assistance; an unforeseen and often sudden event that causes great
damage, destruction and human suffering” 1. The most common types of natural
disasters that often occur are earthquakes, floods, tsunami, typhoon and extensive
fire. Among all the disasters, fire is one of the most dangerous phenomenon.
Fire is one of the essential elements in human’s life and
also a significant source of energy. It acts as a light source in the dark. It
also provides heat for cooking purpose and for warming of bodies of living
things especially during low temperatures. However, misuse of fire can threaten
human’s life and caused damage to building or structure properties which led to
large economic loss of a society. In scientific terms, fire which also known as
combustion is defined as a chemical reaction involving fuel and an oxidizer,
typically the oxygen (O2). 2 The three essential needs of fire are
fuel (i.e. chemicals, gases like hydrogen, papers and etc.), oxygen and heat.
The fire will continue to burn until one of the component is removed.
Figure 1: Fire Triangle
In order to prevent or minimize the occurrence of fire
accidents, the basic knowledge of fire should be known. Fires can be classified
into five main categories based on the type of materials that initiates the
start of fire. (I) Class A fires
usually used to classify the type of fire in ordinary combustible materials
(wood, cloth, paper, rubber and plastics). (II)
Fire in flammable liquids, gases, oil, and paint are classified as Class B fires. (III) Class C fires involves energized
electrical equipment non-conductivity of the extinguishing agent. And (IV) Class D fires are the fires that occur
in the combustible metals, such as magnesium, titanium, zirconium, sodium and
etc. (V) Class K fires are the most
dangerous fire as it deals with cooking oils and greases.
For Class A fires, it is often occur in food storage rooms,
dining areas, restrooms, and refuse storage areas. Some of the fire scenarios
that can be classified as Class A fires are such as fire started in a trash can
which ignited by a cigarette butt or a
plastic container that comes in contact with a range burner. This class of fire
can be easily put out by water based (water and foam or water mist) or a dry
chemical based fire extinguisher. Water and foam or water mist extinguishers
extinguish the fire by removing the heat element. As for the dry chemical, it
interrupts he chemical reaction of the fire triangle.
For Class B fires, the fire often occurs in the maintenance
areas. As an example, aerosol cans exploding due to the storing location very
near to a heat source. This type of fire can be put out by carbon dioxide based
and dry chemical based fire extinguisher.
Class C fires related to electrical equipment, for instance,
when frayed cord comes in contact with water while the machine is still
operating, or overheating of a toaster that caught a fire. Fire extinguishers
with non-conductive materials can be used to extinguish the fire such as carbon
dioxide based fire extinguishers.
As for Class D fires in which combustible metals are
involved, only dry powder extinguishers can be used. These extinguishers are
similar to dry chemical except that they extinguish the fire by separating the
fuel from the oxygen element or by removing the heat element of the fire
triangle. However, they are ineffective on all other classes of fires.
Lastly, Class K fires which often occurs in kitchen; flames
from a grill igniting grease deposits on a hood filter or leaving a frying pan
unattended on the stove. Grease fire can get out of control quickly and spread
from the stove throughout the kitchen into other rooms of the house. Grease
fire can caused serious injury and extensive property damage. Wet chemical of
Class K extinguishers were developed specifically for the modern, high
efficiency deep fat fryers in commercial cooking operations. The wet chemical
extinguishes fire by removing the heat of the fire triangle and prevents the re-ignition
by creating a barrier between the oxygen and fuel elements.
The sources at which the fire first started are very
important as it helps to identify the classification of fires. After knowing
the main source that causes the fire, it is important to use the correct types
of fire extinguisher to put out the fire, as materials in the extinguishers
used will either put out the fire or reacts vigorously with fire causing large
flames and smoke.
HAZARD AND RISK ANALYSIS TECHNIQUE
During engineering design of a structure or building, it is
important to design and perform the fire hazard analysis. Fire hazard analysis
is the technique performed to estimate the potential impact of fire. This fire
hazard analysis technique can be divided into two categories which are the risk
based and hazard based. Risk based method analyses the likelihood of the
occurrence of an event, however, hazard based method does not. The goal of a
fire hazard analysis (FHA) is to determine the expected outcome of a specific
set of conditions called fire scenarios. These expected outcome can be made
based on expert judgement, by probabilistic methods using the past incidents’
data and by deterministic means such as fire models.
Fire hazard analysis is usually used as part of the performance
based design process. It is a straightforward engineering method to perform a
fire hazard analysis. Firstly, it is essential to select a target outcome. One
of the most specified target outcome is to avoid any fatalities in a building.
Next, is to develop a design fire scenarios which helps to determine the fire
source. Determining the fire source is one of the most important part in the
fire hazard analysis. Fire scenario is a set of conditions that defines the
development and the spread of combustion products. However, for a design fire
scenario, it is a set of conditions that defines the critical factors of
determining the outcomes for trial fire protection designs of new building or
modifications to existing buildings. The development of design fire scenarios
are essential as the data determined are very useful for future quantification.
Design fire scenarios should be based on the reasonable expected fires and
worst case fires. Past fire records for the specific building or similar
building are very useful in identifying the conditions that should be avoided.
After determination of the design fire scenarios, a design
fire curve is developed for the design fire scenario or the portion of the
design fire scenario of interest. Once the fire curve is estimated, fire
effects can be predicted. The design fire curve (as shown in Figure 2) is a
graphical representation of the heat release of fire over a period of time. In
another words, intensity of fire is said to be a function of time. Design fire
curve is divided into four phases; ignition, growth, steady-burning and decay.
The design fire curve usually starts at the ignition. Ignition phase is divided
to into piloted and non-piloted. In piloted case, a spark initiates the flaming
whereas in non-piloted case, flaming occurs spontaneously as a result of heat
even in the absence of flame or spark. Different calculation methods can be
used to determine the occurrence of an ignition. The selection of calculation
methods usually depends on the state of fuel whether they are solid, liquid or
gases type. For instance, for a thermally thin solid materials, method of
Mikkola and Wichman can be used, i.e. where Tig and T0 = the
ignition temperature (oC) and initial temperature (oC)
respectively; tig = time to ignition (sec); ? = the density of material (kg/m3);
L0 = thickness of the material (m); c = specific heat of the
material (kT/kg.c); and = the external heat flux and critical heat
flux ignition (kW/m2) respectively.
Following ignition, fire might grow. The growth of fire
depends on the first item that ignites the fire or the spread of fire to the
neighboring items. The rate of fire growth depends on the arrangement and the
type of materials near the fire scene. For the selection of an appropriated
design in fire’s growth, several data need to be obtained; such as the
realistic prediction of the activation of the detector and sprinkler, the time
to start evacuation and the initial exposure of occupants. In 1972, Heskestad
proposed a formula to predict the early fire growth assumption. This is a power
equation that is expressed as:
Where Q = rate of heat release (kW), = fire intensity coefficient (kW/secn),
t = time (sec) and n = 1,2,3.
A steady burning will continue to
occur when a fire scenario involves a fire in an enclosed area. The rate of
burning usually depends on the available ventilation (i.e. the amount of
oxygen) and the available fuel. Simple algebraic calculations can be used to
calculate the fire temperatures in the room. A flashover normally occurs when
the fire will continue to grow until all the combustible items in the enclosed
room are involved. The time at which a flashover occurs can be estimated by
predicting when the fire will reach the minimum heat release rate. One of the
method to predict the minimum heat release rate necessary for a flashover is
known as the method of Babrauskas. In the method of Babrauskas, the minimum
heat release rate is expressed as: where is the area of opening into the compartment
and which represents the height of opening into
the compartment. Lastly, when the fire eventually decrease in size due to the
consumption of the available fuel, depletion of oxygen and suppression, this
process is known as decay. Usually decay is omitted from the analysis.
Figure 2: Design Fire Curve
Once the design curve has been
developed, it would be easy to predict the hazard that would occur. Some simple
fire hazard calculations can be performed for some types of hazards that might
be of interest such as radiant heat flux, smoke production, fire plume and
ceiling jet temperatures and velocities, species production, depth of upper
layer, and toxicity. The simple fire hazard calculations can be performed by
using some simple computer programs and spreadsheets. As we know, many fires
and fire effects are usually not in steady state, hence differential equations
are developed. Numerical technique like Euler method can be used to solve those
differential equations. Besides that, computer models like fire models can be
used. Lastly, all the analysis should be documented complying with the standard
guide published by ASTM; i.e. ASTM E1472-05 Standard
Guide for Documenting Computer Software for Fire Models.
Quantitative fire hazard analysis
has become a fundamental tool in the modern fire safety engineering practice. As
a summary, the flowcharts in Figure 3 shows the steps in performing the fire
hazard analysis technique.
Figure 3: Flowchart of the fire
hazard analysis (FHA) techniques
STUDY OF FIRE DISASTER IN UNITED STATES
In this review report, we look into a case study of fire
disasters that happened in United States for the past 11 years (year 2006 to
year 2016). The information and statistics presented below are mainly obtained
from the annual reports provided by the National Fire Protection Association
(NFPA) survey of fire department. 4-13
Table 1 shows the total number of fire cases reported in
United States from year 2006 to year 2016. The fire cases reported are
classified into 3 main categories; structure fires, vehicle fires as well as
outside and other fires, for instance, forest fires. In figure 4, the graph
shows a decreasing trend on the total number of fire cases reported from year
2006 to year 2016. The chart in Figure 5 shows the overall average breakdown of
the total fire cases in percentage based on each categories; 36% from structure
fires, 15% from vehicle fires and the remaining 49% is due to outside and other
Vehicle fire is defined as fire that involves any types of
mobile properties, such as cars, trucks, buses, motorcycles and any other
highway vehicles: boats or ships; railroad and mass transit vehicles; aircraft
and agricultural, construction and yard vehicles. A vehicle fire event can
occur within a very short period of time and usually involves fatalities and
significant property damage. This kind of fire occur mainly due to the
flammable materials such as flammable liquids like gasoline and oil, which are
commonly found in every vehicle. Taking an example of vehicle fire, leakage of
fuel from ruptured fuel line can interact with the electrical circuit at the
engine compartment. The interaction may lead to sparks and causes fire to
ignite. To minimize the occurrence of vehicle fires, frequent maintenance
should be performed by car owners to ensure that the vehicles are always in
good conditions when vehicles are in used. Besides that, due to the advancement
of technology, nowadays, cars are designed to operate using electric batteries
without the use of fuel, i.e. petrol.
FIRE CASES REPORTED
AND OTHER FIRES
Table 1: Summary of the total number of fire cases
reported from year 2006 to year 2016
Figure 4: The trend of fire cases reported from 2006
Figure 5: The average breakdown of the fire cases
By definition, a structure fire is a fire involving the
structural components of various types of residential, commercial or industrial
buildings. Residential buildings range from single-family detached homes and
townhouses to apartments and tower blocks; whereas the commercial buildings
range from offices to major shopping malls. In this case study, commercial and
industrial buildings are classified under “non-residential buildings” category.
From Figure 6, structure fires reported usually occur at residential buildings.
Table 3 and Figure 7 show the further breakdown of the residential structure
fire based on the types of accommodation; i.e. one or two family houses,
apartments and others.
Table 2: Structure Fire cases from 2006 to 2016
Figure 6: The percentage of structure fires (in
ONE- AND TWO FAMILY HOME
Table 3: Different categories of residential
Figure 7: The percentage of fire cases in
residential buildings (in percentage)
For residential buildings, the most common type of fires is
actually kitchen fire. Kitchen is a
place where a combination of heat, electricity, oil or grease and water can be
found. The most dangerous type of kitchen fire is actually grease fire. This
type of fire can cause serious injury and extensive property damage as this
fire can get out of control and spread easily from the store and kitchen to any
other rooms in the building. Grease fire can happen when leaving a frying pan
on the stove unattended or even during attended cooking, overheating of frying
pan can also catch fire easily. Beside kitchen fires, electrical fires are also
common. Electrical fires can caused by worn out electrical wiring, faulty
electrical appliances or improper use of electrical outlets. A spark can start
a fire when electricity comes in contact with water. Electrical fires usually
occur in older buildings because the old wiring inside the wall might be broken
or worn out. Other than that, old wiring might not be sufficient enough to
handle the amount of electrical appliances in use today. For example, using
bulbs that are of higher wattage than the amount recommended or the overheating
of electrical appliances. Another types of residential fire that can occur is
heater fires. This type of fires is common in countries that have four seasons.
Especially during winter, in the month of December, January and February,
heater are commonly used indoor to keep bodies warm from the cold winter.
Portable heaters usually have automatic shutoff system built-in that will
activate when the heater overheat as a fire precautions. However, coil space
heaters are hazardous. Coil can ignite anything combustible nearby. Hence, it
is always recommended to locate it at somewhere further from combustible items
such as bedding, curtains or furniture.
It is difficult to stop a disaster from occurring completely.
However, preventive measures can be carried out to minimize the severity of the
disaster occurrence. The preventive measures can be divided into 3 stages:
before, during and after the occurrence of a fire. For the first stage, during
the design phase, it is essential to carry out the fire hazard analysis to
predict and estimate the likelihood of the fire event to occur. Past fire
records are one of the important information required for the prediction and
analysis. Fire drills should be carried out at least once a year at offices,
schools, shopping malls or industrial areas such as factories. This practice is
carried out to ensure that occupants are aware of the things to do when a fire
break out. Besides, this also helps them to familiarized with the escape route
to evacuate from the buildings to the safe area which usually known as the
assembly points. During the fire drills, firefighters will demonstrates the way
to put out fire using a fire extinguisher and also educate people on the
different types of fire extinguishers available. As mentioned earlier, not
every types of fire extinguishers can put out fire, as the materials contained
in the fire extinguishers may either put out the fire or react more with the
fire causing smoke. According to the building codes, it is essential for every
buildings to have warning systems such as smoke detector and water sprinkler as
well as fire extinguishers installed in the appropriate locations. During a fire,
several things can be carried out such as determine the main source of fire and
use an appropriate extinguisher to put out the fire. Do not panic, keep calm
and evacuate from the scene to assembly points. It is necessary to provide
adequate space on the route for the fire engines to access to the scene efficiently.
After the fire incidents, the amount of the fatalities and damage on the
properties during the fire incidents should be recorded. This information can
be used to calculate the economic loss in this incidents.
In summary, fire can be very useful, but it can also cause
disaster due to the improper usage of fire. Fire can start anytime and anywhere
with the presence of fuel, oxygen and heat. Fire disaster can be classified
into five different categories; Class A, Class B, Class C, Class D and Class K.
With different classification of fire, different types of fire extinguishers
should be used. It is essential to understand the source of fire and the
correct extinguisher to be used to put out fire. This is because the different
types of fire extinguishers contain different materials, some of the materials
can put out the fire whereas some might react vigorously with the source to
form smoke. Smoke is dangerous as it might contains toxic and excessive
inhaling of smoke may cause suffocation especially in a confined area.
Fire hazard analysis is one of the fundamental tool used in
modern fire safety engineering practice to estimate the potential impact of the
occurrence of fire. It is a straightforward engineering analysis. The predicted
fire hazards are defined as a function of the design fire scenarios analyzed.
It is important to select the most challenging design fire scenarios to
represent the “worst case” scenario. For the fire hazard calculations, it can
be performed simply by hand calculations, spreadsheet which usually used for natal
predictions and also computer programs such as fire models.
It is not possible to stop the occurrence of a disaster
especially natural disasters such as earthquake, floods and extensive fire like
forest fires completely. However, we can predict the occurrence of the event
based on past records’ and developed necessary preventive measures in order to
reduce the severity that caused by the event or the possibilities of fatalities
and property damages to its minimum.
From the case study in United States
reviewed in this report, the most reported fire cases are from forest fires,
structure fires and vehicle fires. Wildfires or forest fires are the type of fire
that spread in over a piece of forest or grassland in a short period of time. When
trees or plants lack of water and becomes dry, fire can be easily ignited.
Besides, plants and trees are usually located very close to each other. Hence, the
rate of fire spreading are very fast. Structure fires especially at residential
buildings are another common types of fires that could possibly occurs due to
the carelessness of human beings or due to worn out electrical appliances.
Therefore, maintenance need to be perform from time to time to ensure we are
living in a safe environment.