Essentials of Fire Fighting
6th Edition
Firefighter I
Chapter 19 — Fire Origin and
Cause Determination
Learning Objective 1
Explain ways to recognize obvious
signs of the area of origin.
19–1
The area of origin contains several
pieces of important information.
Assume
• Precise point of
origin, ignition
• Greatest amount of
damage, debris
• Potentially lethal
concentrations of
gas present
• Monitor air
• Wear full PPE
Area of origin
19–2
Debris on scene contains fire cause
indicators and must remain in place.
Courtesy of Donny Howard
May be used in
court
Arson –
Criminal
charges
19–3
You must control evidence and
remember information from the
incident as much as possible.
Control
evidence
Remember
from on
scene –
What you
Chain of
custody
Required in
legal cases
See
Smell
Hear
19–4
CAUTION
You should minimize fire suppression
and overhaul activities that could
destroy important evidence regarding
the origin and cause of the fire.
19–5
Several factors will influence locating
the area of origin and the overall
success of the investigation.
May be apparent, if not
Critical to overall
success
• Follow from least damage to
most
• Identify witnesses
• Secure scene
• Note initial scene
Incident Commander or
fire/criminal investigator
Wildland or ground
cover fire
• Determine point fire started,
fire cause
• Protect or collect evidence
• May require experienced
investigator
19–6
Courtesy of Donny Howard
The search for area of origin at a
structure fire begins outside.
19–7
You should know actions to take when
the origin cannot be determined.
Delay overhaul beyond
locating, extinguishing
fires
Protect scene
Establish scene security
19–8
Preliminary assessment and exterior
examination require specific tasks.
Exam scene
to determine
Document,
preserve
19–9
Specific
observations
The interior examination begins in the
area of least damage and works toward
the area of greatest damage.
Fire indicators
to use:
Courtesy of Donny Howard
Fire patterns
Melted metal,
glass
Degree of
damage
19–10
Courtesy of Donny Howard
Charring on floors and vertical surfaces
can indicate useful information.
Where fuel burned
in that location
Face toward area
or point of origin
19–11
Area of origin and fire spread factors
should be closely examined.
Multiple areas of
origin
• May indicate intentionally set
• Unintentional may give same
appearance
Factors affecting
fire spread
• Materials in fire’s path
• Building features, layout
• Ventilation openings
• Fire load
• Fire suppression tactics
• Activation of suppression systems
Be aware of
general patterns
• Call investigator if there is a
question
19–12
Courtesy of Donny Howard
Total structural fire loss presents
unique investigation challenges.
19–13
Exterior fires involve several different
types of materials.
Stored materials
Debris
Trash
Rubbish
Ground cover or vegetation
19–14
Ground cover fires require specific
understanding of several concepts.
Basic fire behavior
Effects of winds
Topography
Natural fuels on fire spread
Burns outward in all directions
19–15
Fire burns in equal directions when
on flat ground and without wind.
19–16
The rate and direction of spread of
ground cover fires are affected by
several components.
•
•
•
•
•
•
•
Wind direction
Wind velocity
Terrain/topography
Types of fuel
Ambient temperature
Relative humidity
Moisture content of fuel
19–17
Ground cover fires require specific
understanding of several concepts.
Area of origin may display
• Evidence of slower, less intense fire growth
• Unburned materials
• Effects of flame on fuels less than at head
Radiant heat affects adjacent fuels
• Backsides of grass, trunks protected
• Grass will fall toward area of origin
• White ash product of more complete
combustion
19–18
Finding the area of origin for vehicle
fires is similar to the structural process.
Search for
area of
origin
Interview
witnesses,
firefighters
19–19
Examine
exterior,
interior
Vehicle fires require knowledge and
practice of several safety guidelines.
Ensure
undeployed air
bags inoperable
Ensure shock
absorber bumpers
inoperable
Hybrid, electric car
considerations
Do not cut posts
that contain
restraint systems
Know where large
capacity or
multiple fuel cells
may exist
Hydraulic system
considerations
Check trunk area
for flammable/
combustibles
19–20
WARNING
Do not attempt to access or examine a
vehicle unless you know how to do so
safely.
19–21
REVIEW QUESTION
What ways can a Firefighter I
recognize obvious signs of a fire’s
area of origin?
19–22
Learning Objective 2
Describe the relationship between
fire cause classifications and cause
determination.
19–23
Fire cause determination is a critical
step in the investigation process.
Look for
Determination can
• Competent ignition
source
• Ignition sequence
• Document causes of
fire
• Indicate trends in
unsafe behavior
• Indicate defective
equipment, design
flaws
• Indicate malicious,
illegal behavior
19–24
The National Fire Incident Reporting
System (NFIRS) reports several causes
of fires in structures.
Incendiary
Open flame, ember, or torch
Other heat, flame, or spark
Smoking materials
(Cont.)
19–25
The National Fire Incident Reporting
System (NFIRS) reports several causes
of fires in structures.
Lightning, natural
Heating equipment
Cooking equipment
Electrical or lighting equipment
(Cont.)
19–26
The National Fire Incident Reporting
System (NFIRS) reports several causes
of fires in structures.
Heating, ventilating, and air-conditioning (HVAC) appliances
Other equipment
Exposure
Children playing with matches, lighters, or other ignition sources
19–27
There are four types of fire cause
classifications.
Natural
Incendiary
Courtesy of Iowa Fire
Service Training Bureau.
Courtesy of Donny Howard
Accidental
19–28
Undetermined
Courtesy of Bob Espositio
There are several obvious signs of
cause you should look for.
19–29
DISCUSSION QUESTION
What are some visual signs that may
determine the area of origin for ground
cover fire?
19–30
Absence of an obvious ignition
source can help investigations.
Eliminate
some causes
Focus on other
causes
19–31
REVIEW QUESTION
What is the relationship between fire
cause classifications and cause
determination?
19–32
Learning Objective 3
Recognize signs of arson.
19–33
You will need to provide information if
an incendiary or undetermined initial
cause is indicated.
Gather based on
Different personnel
may perform formal
investigation
• Observations
• Local or state fire
investigators
• Law enforcement
officials
(Cont.)
19–34
Courtesy of Donny Howard
You will need to provide information if
an incendiary or undetermined initial
cause is indicated.
Time of day
Weather,
natural
hazards
Manmade
barriers
People
leaving the
scene
19–35
Additional information should also be
gathered to assist investigators.
Time of arrival
and extent of
fire
Wind direction
and velocity
Doors or
windows locked
or unlocked
Location of fire
(Cont.)
Courtesy of Donny Howard
19–36
Additional information should also be
gathered to assist investigators.
Burglary
tools
Courtesy of Donny Howard
Containers
or cans
19–37
Familiar
faces
Conditions should also be observed to
provide information for investigators.
Unusual odors
Abnormal
behavior of fire
when water
applied
Obstacles
hindering fire
fighting
Incendiary
devices
(Cont.)
19–38
Conditions should also be observed to
provide information for investigators.
Structural
alterations
Trailers
Courtesy of Donny Howard
Fire
patterns
Heat
intensity
19–39
(Cont.)
Conditions should also be observed to
provide information for investigators.
Availability of
documents
Fire detection
and protection
systems
Intrusion
alarms
Location of
fire
19–40
(Cont.)
Conditions should also be observed to
provide information for investigators.
Courtesy of Donny Howard
Personal
possessions
Household
items
Equipment
or inventory
19–41
Business
records
REVIEW QUESTION
How can a Firefighter I recognize
signs of arson?
19–42
Learning Objective 4
Describe the importance of
preserving evidence.
19–43
Learning Objective 5
Explain techniques for
preserving evidence.
19–44
Preserving evidence requires
understanding certain principles.
Responsibility of
all at scene
Protect everything
that looks odd,
suspicious
Do not determine
what is/is not
unless qualified
19–45
There are several important aspects of
protecting the fire scene.
Scene security - First
First-arriving
investigator
• Early security
measures
• Restrict scene
access
• Protect potential
evidence
• Minimize
suppression,
overhaul activities
that could destroy
information
• May adjust or
implement new
measures
• Decision factors
• May request
monitoring of each
entrance, exit to
document individuals
on scene
19–46
Explosions
Structure
19–47
Courtesy of Ron Moore, McKinney
(TX) Fire Department
Establishing a scene perimeter
requires specific knowledge.
There are several ways to establish
perimeters that are both
recognizable and enforceable.
Ensure
initial larger
than needed
Ensure
visible,
recognizable
19–48
Use law
enforcement
or
firefighters
to control
Procedures for criminal investigations
also impact scene security practices.
Keep entry log
Permit access to only those authorized
Move personnel to staging area when tasks complete
Ensure others always escorted
Mark potential evidence to prevent disturbing
19–49
There are several techniques used to
preserve evidence.
Keep evidence
untouched,
undisturbed
Do not gather or
handle unless
necessary to
preserve
Document all
actions
Follow
department SOPs
(Cont.)
19–50
There are several techniques used to
preserve evidence.
Avoid walking
on, crosscontaminating,
or destroying
Avoid excessive
water use
Protect
footprints, tire
marks
Close dampers
and other
openings
Leave charred
documents
Protect
documents from
air flow
19–51
Overhaul operations can be
detrimental to an investigation.
May destroy
potential
evidence
Delay until
origin and
cause
determined
19–52
Begin once
critical
evidence
protected
Courtesy of Donny Howard
Even when a scene is secure,
contamination or spoliation can occur.
Contamination
Spoliation
19–53
Follow local procedures when finalizing
operations and investigations.
After investigation complete
Debris removal
• Secure structure, turn over to
occupant
• Perform according to local SOPs
• Follow local protocol
• May be last activity
• Prevent rekindle
• Separate unburned
• Dump debris where not visible if
possible
19–54
REVIEW QUESTION
What are some techniques
firefighters can use to preserve
evidence?
19–55
Summary
• One of the most important
responsibilities is protecting evidence.
• Use appropriate caution in the area of
origin.
• A thorough investigation can be
conducted to determine the exact
cause of the fire.
19–56