Determining the cause of a fire is the principal task of a fire investigator during the conduct of a post-fire examination of a fire scene.
To do this, an investigator will want to locate the point of origin of a fire. If the point of origin of a fire cannot be identified or if it is determined that it started over a larger area, the term area of origin is used.
From there, a detailed inspection of the area can lead the investigator to the exact cause of the fire. This inspection is done by examining the charred debris and other residues found at the point of origin.
Fires can be classified in two ways: according to cause and according to burning fuel.
These can be used to classify both causes of fires and fires themselves.
These fires involve events that are sometimes called "Acts of God". The most famous example of natural fires are wildfires.
As discussed in the video, wildfires can be caused by lightning, lava, or earthquakes. These are natural events that occur with no human intervention.
Electrical Accidents
Short Circuit
Arcing
Sparking
Induced Current Sudden release of electrical current
Overheating Rising temperatures in an electric circuit beyond that which is tolerable by the device
Pure Accidents
Negligence and other forms of human error
Fires can be identified as intentional if the following are found at the scene:
accelerants - highly flammable chemicals that are used to facilitate flame propagation
plants - combustible materials gathered or prepared at the scene that are utilized to start a fire
trailers - prepared flammable substances that are used to spread fires
These types of fires are based on the types of fuels that were discussed in Lesson 1.2 Fuels, Part 1.
Class A Fire Ordinary Fires
Class B Fire Liquid Fires
Class C Fire Electrical Fires
Class D Fire Metallic Fires
Class K Fire Kitchen Fires