Download - Chapter 12
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Examining the Scene and Finding the Origin
Chapter 12
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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
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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
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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
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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
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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
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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
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Utility Hazards
Figure 12-2A noncontactdetector that willactivate in thepresence of anelectrical current.
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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
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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
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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
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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
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Exterior Examination
Figure 12-3Conflicting burnpatterns on theexterior of thestructure showingwind directiondifferent for eachopening.
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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
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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
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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
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Debris Removal
Figure 12-4 Debristhrown out of thesecond-floor window,hampering a properinvestigation of thefire scene.
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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
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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
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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