© 2009 Delmar, Cengage Learning

Fire Cause

Chapter 13

© 2009 Delmar, Cengage Learning

Objectives

• Describe what needs to be done in conjunction with the search for the area of origin

• Describe evidence found on the exterior of a structure that indicates an explosion

• Describe the importance of identifying the first material ignited

• Describe the four different classifications of fire causes

• Describe identification of the product or person

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Case Study

• Oil furnace was serviced by oil company• Homeowner started furnace next day• It filled the house with smoke and burnt a

section of the basement• Investigator discovered that furnace had not

been properly serviced in over ten years, which resulted in the hostile fire

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Case Study (cont’d.)Figure 13-1 Thefurnace in the areaof origin. The walladjacent to thefurnace is burnedclean.

Figure 13-5 The access area to the heat exchange with the plate turned up out of the way. This area had allegedly been cleaned the day before, but soot and scale are evident, piled up at the face of the opening.

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Introduction

• Knowledge of chemistry and science principles is an invaluable tool

• First vital necessity is locating the fire origin – Might find evidence that will assist you in determining

the cause of the fire – Documenting is critical along the path to the fire origin

• Search for the cause must be done systematically using scientific methodology

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Legal Issues

• Reason the fire service is allowed to stay on the fire scene is to handle the emergency and to identify the area of origin and the cause of the fire– All portions of the structure should be examined

• Even those without damage

• If there is no connection to looking for extension of the fire, then it may constitute an illegal search

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Legal Issues (cont’d.)

• If the investigator uncovers evidence that the fire may be incendiary in nature, the investigation changes focus– It would be prudent for the investigator to:

• Place the scene under guard, keeping all out of the scene

• Approach the proper authority for a search warrant

– If evidence is out in the open and there is a chance that it may disappear or be damaged

• It is acceptable to document, collect, and preserve

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Protecting the Scene

• Protect the scene using barrier tape and guards – Not just in criminal cases: evidence for an accidental

fire is just as crucial in a civil case

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Exterior Examination

Figure 13-7 A trailerof poured dieselfuel that leadsfrom the kitchen,out the door, downthe steps, acrossthe backyard, andbehind an abovegroundpool.

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Exterior Examination (cont’d.)

Figure 13-8 Anevidence tag sittingon top of a bucketthat protects afootprint in the softearth.

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Interior Examination

• What to search for and document– Investigator must search all rooms and areas of the

structure – Search of the structure for extension of the fire and to

eliminate any potential fuel or ignition sources

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Accidental Indicators

• The process of elimination is just as important as confirming a potential correlation between the clues– Presence of smoking materials and burn marks from

cigarettes is evidence but is not proof by itself – Damaged electrical wires and improper electrical

connections in the undamaged areas of the structure is not proof of fire cause but will require investigators closely examine electrical equipment in area of origin

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Incendiary Indicators

• Burn patterns, such as pooling patterns and sharp line of demarcations may be indicative of ignitable liquids

• Common household items stacked and placed in the structure to act as trailers

• Mere presence of an ignitable liquid pattern or even a positive sample is not an indication by itself of an incendiary nature

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Source and Form of Heat of Ignition

Figure 13-9 Carefulexamination ofthe scene revealedmelted plastic thatwas the residueof a 1-gallon milkjug that containedgasoline at the timeof the fire.

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First Material Ignited

• The first material ignited tells the story of what happened

• First material ignited has a form or shape• Some items need a little more clarification

– Plastics take many shapes and sizes and have varying characteristics

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Ignition Sequence

• When a heat source and a fuel do come together, there can be ignition – You must apply science that will prove that the

available heat source was sufficient to ignite that specific first material ignited

• Sometimes the ignition sequence is so obvious that verification need not be documented – Wooden kitchen match dropped onto crumpled writing

paper

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Ignition Sequence (cont’d.)

• If there is any doubt, NFPA texts and documents can verify the ignition temperature of various materials

• Final hypothesis should identify and explain the heat source in detail – Should also identify the first material to be ignited – Explain why the two were in close proximity

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Elimination of All Other Causes

Figure 13-10 Tag left on the gas supply line outside the structure showing that the liquid propane gas bottles had been removed prior to the fire. If there is no date on the tag, thegas provider cangive exact datesof removal andreasons why.

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Classification of Fire Cause

• All fires are considered accidental in nature until proven otherwise

• Natural – Fire was not started by the actions of a human

• Lightning, lava flows, or flooding that creates electrical shorts

• Accidental – Someone made a mistake and some action of a

human resulted in the heat source coming in contact with the first material ignited

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Classification of Fire Cause (cont’d.)

• Incendiary– Many fires are intentionally set, but that does not

make them incendiary• Setting fire to logs in a fireplace

– Key difference between these fires and incendiary fires is the intent

• Key component of this frame of mind is malice

• Undetermined– No matter how good an investigator’s skills, there are

fires that will go undetermined

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Determining Responsibility

• Once the origin has been located, you have a place to look for the cause

• Product– Product failure as a result of design– Product failure as a result of manufacturing – Product is proper, but the instructions were lacking

• Person or persons– Deterrence is a tool in the fire prevention toolbox

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Summary

• It is essential to determine the area of origin • The cause of the fire can fall in the category of

natural, accidental, incendiary, or undetermined • Once the area of origin and cause have been

confirmed, then it may be necessary to identify the persons or things responsible for the fire

• If person involved, investigator must determine whether there was malice