Origin Determination Knowledge Objectives (1 of 2) Describe the recommended techniques for determining the origin of a fire. Explain the need for fire scene reconstruction. Develop and test origin hypotheses. Explain issues of evidence preservation, contamination, and spoliation. Knowledge Objectives (2 of 2) Describe scene documentation techniques. Explain how an investigator determines the point of origin in a room. Skills Objectives Determine a fire s area of origin and point of origin using the scientific method. Accurately reconstruct the area of origin. Analyze a fire scene s data. Introduction (1 of 2) Area of origin Room, building, or general area of point of origin Point of origin Exact physical location where fire began Origin determination and cause determination are closely related. Introduction (2 of 2) Systematic approach should be followed Example: working from area of least damage to area of greatest damage Information sources related to origin Fire patterns, arc mapping Heat and flame vector analysis Depth of char/calcination survey Application of fundamentals of fire dynamics Witness information 1
Overall Methodology (1 of 3) Initial scene assessment Development of preliminary fire spread hypothesis In depth scene examination Reconstruction of fire scene Development of final fire spread hypothesis Overall Methodology (2 of 3) The scientific method is used to determine the origin of the fire. A fire spread analysis must be conducted. Is physical damage consistent with origin hypothesis? Sequential pattern analysis: collecting and organizing the fire pattern data into a sequential format. Overall Methodology (3 of 3) Initial Scene Assessment Provides overall look at structure and surrounding area Important factors Safety assessment Building identifiers Weather considerations In Depth Exterior Examination (1 of 2) Made by using observations, photographs, sketches, or other means of documentation Issues may be brought up later that relate to the exterior. There may be additional fires that occurred. In Depth Exterior Examination (2 of 2) Document: Prefire conditions Utilities Type, location, meter readings Doors, windows, other openings Location, condition, security mechanisms Evidence of any explosions Fire damage 2
In Depth Interior Examination (1 of 2) Consider: Prefire conditions of structure Contents of structure Storage of contents Housekeeping Maintenance Evidence of explosion damage In Depth Interior Examination (2 of 2) Consider (cont d) Areas of fire damage Building systems (HVAC, electrical, fuel gas, alarms, etc.) Composition of wall and floor coverings Position of windows, doors, other openings Fire patterns Relative extent of damage in each area Postfire Alterations Note apparent postfire alterations. Examples: debris removal or movement, content removal or movement, gas meter removal Identify those responsible for alterations. Interview to determine conditions before alterations were made. Debris Removal and Reconstruction (1 of 3) Adequate removal and reconstruction are essential. Remove debris in systematic manner Safety is paramount Remove only what is necessary Move only once Debris Removal and Reconstruction (2 of 3) Fully document scene before use of heavy equipment. Avoid contamination and spoliation. Reconstruction can be limited to the probable area or origin as opposed to the entire area of damage. Debris Removal and Reconstruction (3 of 3) Identify prefire location and orientation of contents. Helpful information can be obtained from: Security cameras Intrusion alarm systems Witness observations 3
Analyze the Data Useful techniques: Heat and flame vector analysis Depth of char surveys Depth of calcination surveys Arc survey diagrams Hypotheses should explain: Where the fire started How it spread Fire Pattern Analysis (1 of 2) Consider all observed patterns. Remember, patterns are altered during the fire. Fire movement patterns are better indicators of origin than intensity patterns. Ventilation can have a dramatic effect on fire behavior and heat release rate. Fire Pattern Analysis (2 of 2) A heat and flame vector diagram is another helpful tool in the analysis. Depth of Char Analysis (1 of 2) Measurements of relative depth of char on identical materials Plotted on detailed scene diagram Influenced by: Single versus multiple heat sources Ventilation factors Consistency of measuring method Depth of Char Analysis (2 of 2) Measurement of the relative depth of calcination is another useful measurement Observable physical changes in gypsum wallboard The finish on the wallboard can influence heat effect. Water applied during fire suppression can soften the wallboard Cross sectional inspection may be used Arc Mapping (1 of 3) Identification of locations of electrical arcing to help determine area of origin Arc sites in a building can form a pattern. Technique can be difficult due to: Melting of conductors Postfire re energizing of the electrical system (and subsequent arcing) 4
Arc Mapping (2 of 3) Procedure Identify and diagram areas to be surveyed. Establish zones. Identify and inspect conductors Determine whether result of arcing, environmental, or eutectic effect Plot location of arcing events on diagram. Mark locations of arcing on conductors Collect and preserve items Arc Mapping (3 of 3) Electrical arc survey diagram. Testing Hypotheses (1 of 2) Based on analysis of all data, hypotheses can be developed and tested using: Time line analysis Fire modeling Experimental testing Testing Hypotheses (2 of 2) A valid origin hypothesis is consistent with all data and answers these questions: Can a fire starting at the hypothesized origin result in the observed damage? Is the growth and development of a fire from this origin consistent with the timeline? Is there a competent ignition source at the hypothesized origin? Selecting the Final Hypothesis After hypotheses are tested, only one should survive. Review the entire process. Be sure all credible data are accounted for. Document facts that support final hypothesis Attempt to resolve contradictions. Review by other investigators may occur In cases of large fire losses, personal injury, death Origin Insufficiently Defined Inability to determine the origin does not necessarily preclude cause determination. Explain why origin cannot be narrowed to reasonable size Eyewitnesses to early stages of fire may provide reliable evidence. Total burn is difficult fire scene to investigate But not impossible 5
Summary (1 of 7) Area of origin refers to the room, building, or general area where the point of origin is located. The point of origin is the exact physical location where a heat source and a fuel come into contact with each other and a fire begins. Summary (2 of 7) Recommended methodology for examination of a fire scene includes: Initial scene assessment Development of a preliminary fire spread hypothesis In depth scene examination Reconstruction of the fire scene Development of a final fire spread hypothesis Summary (3 of 7) Care should be taken to limit damage to any potential ignition sources, initial fuels, or other important evidence identified during excavation of the scene. Summary (4 of 7) Persons familiar with the involved structure can provide useful information about prefire conditions and fire protection systems. Summary (5 of 7) The origin hypothesis should explain not only where the fire started but how it spread throughout the structure, and it must be supported by evidence gathered through the fire investigation. Summary (6 of 7) Fire pattern analysis, depth of char analysis, and arc mapping are techniques employed by the investigator. Once the origin hypotheses have been tested, only one should survive. 6
Summary (7 of 7) The inability to identify the point or area of origin does not, in and of itself, preclude a valid determination of cause. 7