6.

2 Basic principles in Fire and Arson investigation

FIRE INVESTIGATION

This chapter will point out the main features of fire Investigation. Fire
investigation is by nature the basis for fire prevention program. Only an in-depth
analysis of what sequences of events enable a fire to start, enabled it to spread,
and how and where it was controlled (e.g., firefighting, structural design, lack of
fuel) can help prevent future fires. Additionally, fire investigation includes the
observations of everyone involved, and at the fires themselves there are many
firefighters who will able to shed light on the nature of the fire, its progress,
and so forth.

One of the most difficult problems to solve is to determine the cause of the fire,
since the flames generally consume any evidence of what occurred. This is the
reason that the cause of most fires cannot be determined without a long and careful
investigation.

Firefighters often make snap judgments at the scene as to the cause of a fire,
without an adequate evidence or sufficient investigation on which to base their
decision. Apparently, there is hesitation on the part of the firefighters to admit
that they do not really know the real cause of the (approximately 4% of those
reported) are listed as �cause known.� Instead, the fire is attributed to various
causes without apparent regard to actual evidence or to lack of it.

Some of the favorite causes listed by firefighters, when they are not certain of
the actual cause, are faulty wiring, children playing with matches, spontaneous
combustion, sparks from stove, burning rubbish, and careless disposal of smoking
materials.

The very general and indefinite nature of these causes indicates that, in most
cases, they are based on assumptions, rather than on evidence.

In this relation, the material or book will assist you in performing or conducting
investigation to determine the causes and origin of a fire.

No matter how small, fire must be investigated. Fire investigations provide

authorities with information needed to guide fire prevention educational programs,
help fire inspectors in spotting and eliminating new or previously overlooked
hazards, and develop meaningful information for training fire protection personnel.

As far as fire investigation is concerned, they must be defined as:

� Cause - that which made the fire start; and

� Reason - that which led to the cause of a fire (a motive leading to the action).

Both cause and reason must be established to satisfactorily complete a fire

investigation. The �cause� explains the existence of fire, or the WHAT of
investigation; while the �reason� establishes the WHY of the fire and
investigation. Both are required to correctly classify the fire, and also to
provide guidance in establishing corrective action to preclude a recurrence of the
incident.

The importance of the establishment of a fire cause is the knowledge of the

physical aspects of fire.

Four General Classes of Fire Causes

1. Natural Fire
fire caused naturally without human intervention or aid; such as lightning,
spontaneous ignition, mechanical malfunction of equipment.

2. Accidental Fire
fire causes where human action is involved directly or indirectly. i.e. a).
Careless disposal of smoking materials; b). workers using welding-cutting equipment

3. Arson
fire cause as a result of the willful and criminal action of some persons, i.e.,
incendiary fire.

4. Unknown Fire
fires which are not classified as to cause.

Three General Classifications of Fire

1. Innocent fire - e.g. natural and accidental causes

2. Incendiary fire - e.g. arson cases
3. Unknown fire - e.g. fire of unknown causes.

Fire Investigation and Evidence Kit

Evidence kit provides equipment for use in the investigation and for the
preservation of any evidence found at the scene after that evidence has been
photograph in its original location.

� Special clothing such as: coverall, gloves, boots used to protect uniform;

� Flashlight and electric lantern;

� Measuring tape and small ruler for making measurements;

� Labels (gummed and stringed) used to identify items;

� New or sterile glass jars with rubber airtight seals used for the collection of
samples;

� Envelopes, boxes, plastic bags, metal cans used for the collection (assorted
sizes) used for collection of samples.

Basic Steps in a Fire Scene Examination

Search systematically

Observe

Take photograph

Work by the Process of Elimination

Check and Verify

Take Note

Draw diagrams

Areas to Conduct Fire Investigation

Exterior

Determine where the fire vested first by comparing burn char, smoke, and heat
patterns around windows, doors, and roof.
Look for the following:

� exterior points of origin;

� unusual, burn patterns of flammable liquid;

� tools and flammable liquid containers;

� footprints and scuff, marks at suspected points of entry.

Interior

Conduct a cursory examination or general survey of the entire structure of interior

for the extent of fire damage. Establish the class of fire duration approximate
burn time by checking the following:

� Window glass condition;

� Depth of wood char, at or in close proximity to the point of origin;

� Penetration of fire restrictive wall coverings by fire;

� Electric clock that has been stopped by fire damage.

� Note the time stopped and compare with alarm time. The time factors should be
estimated and considered as approximation only.

Steps on How to Determine the Point of Origin

1. Examine the entire interior of the building and determine which room or areas
have received the most severe fire damage. Generally, this will be the area where
the fire burned extensively or the longest and will very likely be where it
originated.

2. Determine the level or origin within the room by examining and comparing the
bottom side of the tables, shelves, and chairs.

3. Examine the ceiling and look for the following patterns:

a) fire penetration and

b) heaviest fire exposure

4. Examine the light bulbs within the room. The side of the bulbs which is
initially exposed to heat begin to swell or bulge and lose shape at about 900 �F
when exposed to heat for 10 minutes or more actually point to the area of fire
origin.

5. Examine walls within the room and look for fire patterns or fire cones. Fires
generally burn upward and outward, leaving corresponding fire patterns on wall as a
result of heat transfer through convection and radiation. The steepness or
relative, pitch of the angle seen on the fire cone is indicative of the type of
burning, e.g smoldering or flaming
Debris

Examine the fire debris and the floor in the following manner:

� Conduct a detailed search of the debris, examining it layer by layer until the
floor is reached;

� Completely clean the floor on all debris and char dust. The floor and floor
covering should be clean enough to observe and photograph the significant burn and
char patterns -and should be dry.

� Carefully reconstruct and replace furnishings and other articles in their

original positions by using burn patterns and corresponding protected areas. During
fire progress, legs and bases of furniture and other items on the floor will
protect the floor, leaving unburned marks which will aid in repositioning.

� Examine the floor coverings and floor for significant patterns.

Furnishings

Examine fire damaged furnishing such as: upholstered furniture couches, chairs,
beds, etc.

Two (2) General Types of Burn Pattern

� Burn pattern that involves a surface burning of the item. This pattern is
indicative of the presence of a smoldering source of ignition. Examination of
supporting springs will disclose that tension still exists.

� Burn, patterns involving deep penetration of one portion with corresponding

collapse of springs and frame destruction: Spring collapse is caused when the
heating process occurs over an extended length of time, causing the springs to lose
their tension and collapses of their own weight.

Types of Fire/Arson Investigation

Basic Investigation
Purposes:

1. to determine what property was damage;

2. what the causes and reasons were;
3. the number and extent of injuries or fatalities; and
4. the recommended corrective actions to prevent recurrence.

Technical Investigation

It is an in-depth investigation to determine more specific details of the cause and

effects, and to establish necessary corrective action.

Reasons in Conducting Technical Investigation

1. there is suspicion of arson in connection with any fire;

2. there is suspicion of negligence or violation of regulations;

3. the cause of any fire is undetermined (to establish the most probable cause);

4. there is evidence of negligence or mismanagement in the fire suppression or

rescue operation,

5. loss of life or disabling as a result of fire.

Arson Investigation

The direct result of the basic or technical investigation or it may be brought

about from outside knowledge.

FIRE SUPPRESSION, CONTROL AND EXTINGUISHMENT, AND EXTINGUISHING AGENTS

The proper selection of an agent or method of control or extinguishment is the most
important factor in determining the degree of a success of a firefighting
operation.

Fire Suppression - means showing down the rate of burning, whereas, control means
keeping the fire from spreading or holding the fire to one area. Extinguishment is
putting the fire completely out.
Four Methods of Fire Extinguishment and How It Works

Extinguishing fire is somewhat comparable to the elimination of life. For example;

the cooling of the fire may be compared to asphyxiation (elimination of the oxygen
supply), and separation may be compared with malnutrition or starvation. The
tetrahedron concept adds a fourth element - chemical reaction.

Under the triangle-of-fire-concept, there are three (3) ways of suppressing,

controlling, and extinguishing a fire, namely:

1. Cooling
The cooling process uses an extinguishing agent whose primary characteristic, is
heat absorption. Water is the best general cooling agent for firefighting purposes.
Used on Class A fires, the water absorbs the heat generated at the surface of the
burning material, thus, reducing the temperature of the material below its flash
point.

2. Smothering
excludes the oxygen from the fuel so that the gases or vapors of the fuel cannot
ignite and continue the combustion. CO2 and AFFF are used for this purpose.

3. Separation
The removal of the fuel, as in the example of turning off a valve in a gas line
prevents the fuel and oxygen from coming together. If fuel is not available, then
heat, regardless of the temperature, cannot affect the fuel, Therefore, there is no
fire.

These three methods of extinguishment explain how fires are extinguished with the
used of water, CO2, and foam. They do not entirely account for the results obtained
by vaporizing liquids or dry chemicals.
Vaporizing liquids could not possibly absorb enough heat to have the same effect as
water, and dry chemical do not exclude sufficient oxygen to smother a fire in the
same manner as carbon dioxide.
The next paragraph will explain the fourth element, the chemistry of fire in terms
of the theory of reactivity.

4. Chemical Chain Reaction

The fourth method of extinguishment is known as inhibition or the interruption of
chemical reaction.

The sequence of events in suppressing or extinguishing a fire with dry chemicals or

vaporizing liquids includes some aspects of the first three methods.

Using the potassium bicarbonate (dry chemical) as an example, you can follow the
process of the fourth method of extinguishment. Remember this is a rapid reaction
and does not necessarily happen one step at a time.

First, the heat of the fire vaporizes the potassium bicarbonate thereby producing
water, carbon dioxide, and potassium dioxide. In the process of vaporization and
the change of these compounds, a substantial amount of heat is absorbed by the
water and some smothering occurs due to the release of CO2.

Second, the chemical reaction resulting, when the potassium dioxide unites with the
water formed by the fire creates an amount of potassium hydroxide.

Third, some potassium hydroxide reacts with certain products released from the
fuel, thus forming water and potassium monoxide. Other potassium hydroxide
molecules react with the free hydrogen of the combustion to form� a potassium atom
and molecules of water.

Finally, this combination of reactions halts the process of fuel uniting with
oxygen of the air, thereby breaking the chemical chain reaction and stopping the
fire.
Extinguishing Agents

The effectiveness of an extinguisher on a particular fire depends on the amount and

type of agent in the extinguisher. Different extinguishing agents can be used to
put out a certain class of fire by one or more methods.

1. Removing oxygen;
2. Removing the fuel;
3 Removing heat; and
4. Interrupting the chemical chain reaction.

Some extinguishing agents may be able to extinguish more than one class of fire.
They are marked with multiple letters or multiple numerical-letter ratings.
The following are the most common extinguishing agents, the class of fire they are
used, and the extinguishing methods used:

1. Water
Used only on Class A fires. Water is the most effective in cooling the burning
material below its ignition temperature. It is the most commonly used agent in
firefighting.
In its natural state, it is highly stable and may be used to extinguish most types
of fire if properly applied. Due to its conductive properties, water should not be
used on electrical fires.

Additives:

There are many additives for water used in firefighting. Each of these has a
specific purpose and effect on the water.
Ways or Methods Water Extinguishes Fires

Cooling
The outstanding heat absorbing qualities of water make it an excellent cooling
agent. In the cooling process, water is applied in large enough amounts to reduce
the temperature of the surface of the burning material to below its flashpoint. The
amount of water required depends on the burning material (temperature) and the
manner in which water is applied (straight or fog stream).

Smothering

When water is used to smother a fire, stream must be generated in sufficient

amounts to exclude or displaced air. If the steam generated is confined in the
combustion zone, the smothering action will be enhanced. In ordinary combustibles,
the cooling effects of the water not the smother - normally causes extinguishment.
The smothering effect does not completely extinguish the fire; rather, it has a
tendency to suppress flaming.

Usage

Water is generally used on Class A fires. Fires involving high flashpoint liquids
(such as heavy fuel oil, and asphalt) may be extinguished when water is effectively
applied in spray form. Water may also be used to extinguish Class C and Class D
fires in some cases. In these cases, use extreme caution to avoid injury to
personnel and/or damage to equipment.

2. Carbon Dioxide (CO2)

A number of its properties make CO2 a desirable extinguishing agent. It is non-

combustible and non-reactive with most substances. CO2 provides its pressure for
discharge from storage cylinders or extinguishers. Being a gas, CO2 can penetrate
and spread to all parts of fire.

Effects:

Extinguishment with CO2 is primarily by smothering. It covers or blankets the

burning materials and reduces the oxygen content to below levels needed for
combustion. Even though it is very cold, it has a little cooling effect on a fire
when compared with equal amounts of water. This is the reason when fires that have
been apparently extinguished with CO2 re-ignite from hot surfaces or embers as the
CO2 dissipates.

Usage:

Due to its non-conductivity, CO2 is very effective for use on Class C fires. It is
also used on Class B fires, but another agent is needed in blanketing or smothering
on large are fires to prevent re-ignition.
CO2 can cause unconsciousness and death in connections needed for extinguishment. A
9% concentration is about all most people can take without becoming unconscious
within just a few minutes.

3. Dry Chemical

The dry chemical extinguishing agents in use today are mixtures of powders and
various additives that improve the storage, flow, and water repellency of the
powders. Sodium bicarbonate, potassium bicarbonate, and mono ammonium phosphate are
some of the powders commonly used today. Dry chemical is stable at low
temperatures, but it has an upper storage temperature of 140 �F. At temperatures
above 140 �F some caking or sticking of the powder occurs. These agents are said to
be non-toxic, but in discharging large amounts they may cause some breathing and
visibi1ity problems.
Effects:

Flames banish almost at once when dry chemical is applied directly to the fire
area. But the exact chemistry and mechanism of the extinguishing agent are not
fully known. It has been suggested that the dry chemical agents inhibit the chain
reaction in the combustion zone has a greater effect in the extinguishment than the
smothering or cooling actions and radiation shielding have.

. Dry Powder

Dry powder is a generally term for agents used to extinguish combustible metal
fires. No one dry powder has been found to be effective, on all types of
combustible metals.
Effects:

Dry powder generally extinguishes fires by excluding air from the combustible
metal. To some extent, heat is absorbed by the powder to lower the temperature of
the metal to below ignition point (as with G.I. powder).
Usage:

Dry powder is used primarily on Class D fires and should not be used on other types
of fire, due to its limited value on these fires.

5. AFFF
Aqueous Film Forming Foam has replaced protein foam for all around firefighting
purposes. Protein base foam is now used primarily for runway foaming operations and
for some training purposes.

Effects:

The quick �knock-down� and �heat reduction� properties of AFFF have provn it to be
a highly effective agent. These properties, combined with its ability to seal the
surface of burning hydrocarbon fires to prevent �flashback�, make it an outstanding
and effective extinguishing agent with which to work. When AFFF is applied to the
surface of a flammable liquid fire, the surface active material (surfactant)
provides a vapor sealing effect. This is not only extinguishes the fire but also
prevents the release of fuel vapors which could result in flashbacks. This vapor
seal is also very hard to break-up by walking, or moving some hose lines through
it.

Usage:

As with any other extinguishing agent, its effectiveness depends on the proper
application. The AFFF is designed to be applied at a 6 % mixture (94 parts water to
6 parts AFFF concentrate). This mixture should be applied in a rainfall manner, or
lobbing effect to allow rapid spreading over the surface. It is used primarily to
extinguish on Class B fires. It may be used on Class A fires but may be less
effective than plain water. Foam spray (fog) is more conductive than plain water
fog, because the material contained in the foam allows the water to conduct
electricity.

6. Halons (Halogenated Agents)

These agents have been used for over 50 years. Continuous research has brought
these agents to the present high degree of effectiveness in interrupting the chain
reaction they possess along with a decrease in life safety hazard.

The older (better known) agents such as carbon tetrachloride (Halon 104) and
chlorobromomethane (Halon 1011) are less effective and more toxic than the newer
agents now in use.

Effects:

Halogenated agents work chemically to extinguish fire. They stop combustion process
by breaking the fire chain reaction and prevent further fire propagation. This
chemical fire-stopping action happens with only a low concentration of halogenated
agent used. Application of the agent may be applied locally by using a compressed
bottle of noncombustible gas similar to a carbon dioxide fire extinguisher. This
type of application is effective in controlling or extinguishing surface fires
involving flammable liquid, solids, or gases, such as dip tanks, quench, tanks,
spray booths, oil-filled transformers, or vapor vents.

Usage:

Halogenated agents are very effective on Class B and Class C fires and have some
effects or success on Class A fires.