Upgrade to remove ads
Chapter 19: Fire Origin and Cause Determination
Terms in this set (37)
Area of Origin
The general location (room or area) where the ignition source and the material first ignited actually came together for the first time.
Point of Origin
Exact physical location where the heat source and fuel come in contact with each other and a fire begins.
The sequence of events that allow the ignition source and the material first ignited to come together.
Crime of willfully, maliciously, and intentionally starting an incendiary fire or causing an explosion to destroy one's property or the property of another. Precise legal definitions vary among jurisdictions, wherein it is defined by statutes and judicial decisions.
Chain of Custody
Continuous changes of possession of physical evidence that must be established in court to admit such material into evidence. In order for physical evidence to be admissible in court, there must be an evidence log of accountability that documents each change of possession from the evidence's discovery until it is presented in court.
The apparent and obvious design of burned material and the burning path of travel from a point of fire origin. Previously known as burn pattern.
Competent Ignition Source
A competent ignition source will have sufficient temperature and energy and be in contact with the fuel long enough to raise it to its ignition temperature.
History of the fire, beginning when the ignition source and the first fuel ignited meet at the area of origin, and proceeding through the entire duration of fire spread through the scene.
Combustible material such as rolled rags, blankets, newspapers, or flammable liquid, often used in intentionally set fires in order to spread fire from one area to other points or areas.
Material or chemicals designed and used to start a fire.
General term referring to anything that can taint physical evidence.
Term that refers to evidence that is destroyed, damaged, altered, or otherwise not preserved by someone who has responsibility for the evidence.
What are some ways to determine the area of origin?
- Follow physical indicators from the area of least damage to the area of most damage.
- Identify witnesses, secure the scene, and note initial scene observations
Preliminary Scene Assessment and Exterior Examination
The first part of an examination of a structure fire. It consists of an examination of the entire incident scene to determine its size and scope and to determine whether it is safe to continue working in the structure.
- Building damage
- Fire and ventilation patterns around windows and doors and under the roof eaves
- Means of ingress and egress
- Utility services
- tire tracks or footprints
- discarded containers
- indications of forcible entry around doors and windows
- presence or location of surveillance cameras
The second part of an structure fire examination. Work from the area of least damage to the area of greatest damage. Use the following fire indicators to determine the path of fire spread and the area of origin.
- fire patterns
- melted metal and glass
- degree of damage to structure and contents
What factors affect fire spread and should be evaluated during the scene examination?
- The nature and composition of the combustible materials in the fire's path.
- Building features and layout that assist in or resist fire spread.
- Ventilation openings and their size and location.
- Combustible materials present (fire load).
- Fire suppression tactics.
- Activation of fire suppression systems.
Where would the point of origin be located in a ground cover fire on flat ground with a consistent fuel bed and no wind?
The fire would burn equally in all directions, and therefore the point of origin would be in the centre of the circular fire pattern.
What affects the rate and direction of spread of ground cover fires?
- types of fuel
- ambient temperature
- relative humidity
- moisture content of fuel
What safety guidelines should be used when examining vehicles?
- Ensure that undeployed airbags are inoperable
- Check shock absorber bumpers to ensure they are inoperable.
- Do not cut through door posts on hybrid and electric cars because they carry a high electric charge.
- Do not cut posts on some cars that contain seat belt restraint systems because they can explode if they are cut.
- Be aware that large capacity or multiple fuel cells may exist on light trucks, motor homes, buses, and large trucks.
- Remember that hydraulic systems on refuse trucks, dump trucks, and other commercial vehicles can explode when exposed to heat.
- Check the truck area for propane tanks or flammable/combustible liquid containers.
What are the three things you must look for to determine the fire cause?
1. Competent ignition source
2. the material that first ignited
3. The action that brought the above two together.
What does determining fire cause accomplish?
- Document the causes of fires which help to prevent similar fires from occurring in the future.
- Indicate trends in unsafe behaviour that can be corrected through educational programs.
- Indicate the existence of defective equipment or design flaws that need to be corrected.
- Indicate malicious or illegal behaviour to be used in arson cases.
What are the four classifications of types of fire cause?
1. Accidental - Do not involve a deliberate human act to ignite or spread the fire. Can result from unsafe human behaviour (smoking in bed), unsafe conditions (overloaded electrical circuits), or hazardous processes (concentration of dust in grain silo).
2. Natural - Occur when humans are not involved. Lightning or materials self igniting.
3. Incendiary - Deliberately set under circumstances in which the responsible party knows that the fire should not be ignited. (Arson)
4. Undetermined - When the specific cause has not been determined to a reasonable degree of probability.
What is the most obvious sign of fire cause and why?
The presence of a competent ignition source (heat source) because other parts or the fire triangle (oxygen and fuel) are almost always present.
What are some common ignition sources?
- Cook top
- Electrical appliances
- Exposed wiring
- Electrical receptacles
- Open fires
What are some signs of arson?
- Time of Day
- Weather and natural hazards
- Man-made barriers
- People leaving the scene
Whose responsibility is it to preserve evidence at the scene?
All fire officers and firefighters.
What makes a secure fire scene?
When the scene has a recognizable perimeter and someone to maintain that perimeter.
Whose responsibility is it to initially secure the fire scene?
The fire suppression personnel who respond to extinguish the fire.
What are some early scene security measures?
- Restricting access to the scene
- Protecting any potential evidence
- Minimizing fire suppression and overhaul activities that could destroy important information regarding the origin and cause of the fire.
How large should the perimeter be for explosions?
1.5 times the distance from the farthest piece of debris found.
What are the three primary categories of evidence?
1. Direct Evidence - Facts to which a person can attest without further support. (Witness accounts)
2. Circumstantial Evidence - Supports an inference formed from direct evidence.
3. Physical Evidence - Physical objects like electrical conductors, photographs/film, gas can, fire patterns, etc.
In most jurisdictions, who has the legal responsibility for determining the origin and cause of a fire?
The fire chief, who delegates this authority to fire officers and firefighters at the scene.
What are some things first-arriving firefighters should note?
- Vehicles and people present at the scene
- Status of doors and windows (locked or open)
- Evidence of forced entry
- Condition of contents of the rooms, whether in unusual order, ransacked, or unusually bare.
- Indications of unusual fire behaviour or more than one point of origin.
What is the role of the fire investigator?
Fire marshals, fire inspectors, and fire investigators are responsible for conducting detailed investigations and analysis beyond the initial determination of fire origin and cause.
What is the role of insurance investigators?
They determine the cause, amount of loss, and in some cases liability for fires involving property they insure. Insurance companies may employ insurance adjusters who visit the incident site, collect police and fire reports, create diagrams, interview witnesses, and take photos of the scene on the insurer's behalf. Insurance investigations are made independently from law enforcement/fire investigations but they may compare their findings.
What gives fire department personnel the right of entry when responding to an emergency.
Exigent circumstances. They can remain until they relinquish control of the scene, after which they require the owner's permission or a warrant to re-enter the scene.
Can fire department personnel remove property that may be relevant to fire origin or cause?
Yes but they require the owner's permission or a warrant.
THIS SET IS OFTEN IN FOLDERS WITH...
Chapter 18: Loss Control
Chapter 16: Fire Streams
Chapter 20: Fire Protection Systems
Chapter 15: Fire Hose
YOU MIGHT ALSO LIKE...
Chapter 19: Fire Origin and Cause Determination
fire science chapter 19 - fire origin and cause de…
Chapter 38 Fire Cause and Determination
Chapter 38 Fire Cause and Determination
OTHER SETS BY THIS CREATOR
Chapter 10: Rescue Tools, Vehicle Extrication, and…
Chapter 23: Hazards, Behaviour, and Identification…
Chapter 7: Portable Fire Extinguishers
Chapter 17: Fire Control