Chapter 12

© 2009 Delmar, Cengage Learning

Examining the Scene and Finding the Origin

Chapter 12


Objectives

• Describe what to look for on the exterior of the structure that would indicate the area of origin

• Describe what to look for when examining the interior of a structure

• Describe the steps taken to do a fire scene reconstruction and the benefits obtained from such an effort

• Describe events or conditions that may create greater char, skewing the path of fire travel


Case Study

• There were evident burn patterns on the outside of a resort-type home

• Working from the least damaged area to the most damaged area was hard

• The area of origin was floor level in the kitchen on the east wall

• Interviews with the occupants divulged that when they left the house, they emptied the ashtray they had been using into the trash can


Introduction

• You cannot find the cause of the fire until you have located the area of origin

• Investigators must work their way through the fire scene interpreting the burn patterns to find the area of origin


The Assignment

• There must be a comprehensive policy and procedure on how fires are to be investigated by the locality

• The national fire incident reporting system (NFIRS) has an entire section on the origin and cause of the fire to be filled out by the fire officer in charge (OIC)

• Fire investigator refers to the person who examines the scene


Systematic: A Process

• Approach must be systematic and consistent– Must follow a logical path that is conducive to

identifying the fire area of origin– Can prevent overlooking key indicators and evidence – A common approach is working from the least

damaged area to the most damaged area• Smoke patterns and burn patterns can be the path to

the area of origin


Safety Issues

• Safety is the first and last concern• Structural stability

– Knowledge of proper building construction is essential– Heavy technical teams can help shore up structures– Sometimes damage may be so severe that the only

recourse is to demolish structural elements • Crane or other heavy equipment can be called in to lift

damaged items away from the structure


Utility Hazards

Figure 12-2A noncontactdetector that willactivate in thepresence of anelectrical current.


Secure the Scene

• Efforts should have been made to cordon off the area for the safety of the general public

• Security must be maintained throughout the investigation – Monitor the exterior while the investigator is inside the

structure


Examining the Scene During Suppression Operations

• In an active burning fire, investigation is not a primary function of the suppression officer– Engine company officer usually will not have the

quality equipment or the opportunity to take photos of the scene

– However, if there is time, the engineer or other personnel may be able to snap a few photos

• Camera can use a standard 35-mm film that requires processing, or the camera can be digital


Examining the Scene During Suppression Operations

• For larger events, the investigator will be assigned and will report to the OIC

• Investigator may find it beneficial to go into the structure even before the fire has been completely extinguished – Should only be done if the investigator is completely

qualified to work in an imminent danger to life and health (IDLH) atmosphere and has proper equipment


Examining the Scene During Suppression Operations (cont’d.)

• If the OIC feels that it is not safe for the investigator to enter, it is prudent for the investigator to comply


Exterior Examination

Figure 12-3Conflicting burnpatterns on theexterior of thestructure showingwind directiondifferent for eachopening.


Building Systems

• Compartmentation is a component of the building system

• Walls should have a fire rating as in the use of sheetrock

• Fire investigators must be familiar with:– All forms of sprinkler systems– Fire-extinguishing foam or dry chemical extinguishing

agent delivery systems

– Total flooding systems such as CO2 systems


Building Systems (cont’d.)

• Include the examination of utilities such as the heating, ventilation, and air conditioning system

• Key issue is the impact building systems had on the fire growth and the extension of the fire to other areas of the building


Interior Examination

• Before entering the structure, the investigator must assess the safety of the structure

• Examine burn patterns to interpret the relative length of time the fire burned in each area – Lowest burn is of importance because fires naturally

burn upward and outward – Use tools such as the depth of char gauge on wood

char and check calcination to help to determine the relative burn times


Debris Removal

Figure 12-4 Debristhrown out of thesecond-floor window,hampering a properinvestigation of thefire scene.


Examining Contents

• Patterns on contents can be vital to the discovery of the area of origin – Can support patterns on walls, ceilings, and floors– Can help resolve any confusing patterns in the

structure

• Burn patterns on furnishings can show the direction of fire travel


The Area of Origin

• With careful examination of all burn patterns, the area of origin can be identified

• A successful hypothesis can be tested only after a systematic search of the entire fire scene– Any conflicting patterns must be taken into account


Summary

• Safety has to be the first concern of everyone on the scene

• An accurate determination of the area of origin of the fire is the first step in the final determination of the fire cause

• With the application of a systematic search along with scientific methodology, the investigator can usually locate the area of origin

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Chapter 12