Wildfire Origin and Cause Investigation - Part 2

In Part 2 of “Wildfire Origin and Cause Investigation,” we will continue to discuss the main points for the local fire investigator to focus on when conducting a wildfire investigation. Hopefully, last month’s article was an eyeopener for some local...


Debris burning: The debris fire is similar to the campfire. These fires are used to burn garbage and other controlled burning. Indicators of a debris fire are burn barrels or incinerators. Make sure to check the condition of burn barrels for failure. The witness interview and burn-pattern indicators are the best way to confirm this type of cause.

Smoking: Discarded smoking materials have been used as a cause for many wildland fires; however the investigator must be sure that certain conditions are identified before using this cause. Under normal conditions, cigarettes generally will not start wildland fires. Remember the RH must be less than 22%. The glowing tip must be exposed to fine fuels and the tip must be oriented into the wind. The ideal outside temperature is 80 degrees Fahrenheit or greater.

This writer has conducted experiments with smoking materials at a recent fire investigation training seminar. A time-delay matchbook device using cigarettes was constructed and failed to ignite. The devices were constructed with a few different types of cigarettes and extinguished themselves in a short period of time. The investigator should keep in mind that cigarettes come from all over the world and not all are the safe type.

Railroads: Railroad fires are caused by rail operation, personnel and rolling stock. Indicators for a railroad fire include fires along active tracks with multiple areas of origins. Examine tracks for recent repair or maintenance issues. Conduct witness interviews to see if a train has passed recently. The investigator should check with other jurisdictions for recent fires along train tracks. When conducting an examination on or near railroads ensure that the train traffic is shut down and obtain confirmation of the shutdown.

Children: This type of fire is usually started by a child 12 years old or younger. The child firesetter may be motivated by curiosity or vandalism. The child firesetter usually will set fires with a group and is influenced by peer pressure. Indicators are fires located near foot paths, trails, schools or playgrounds. The child firesetter may use lighters, matches, or fireworks as an ignition source. The investigator must follow all department policies and procedures when interviewing children. The investigator should refer the juvenile to the local fire prevention office for placements in a juvenile firesetter intervention program, however, follow your department’s procedures.

Equipment: The investigator should identify any equipment in the area of origin such as mowing, grading, construction logging and land clearing. There are five main ignition sources that can cause equipment fires.

  1. Exhaust particles
  2. Lubricant and fuel
  3. Friction
  4. Radiant or conductive heat
  5. Mechanical breakdown

Exhaust particles: Particles from any internal combustion engine can cause a fire. The catalytic converter can reach exterior temperatures of 1,200 degrees Fahrenheit. The particles of the catalytic converters are a major cause of fires. These types of fires are usually located on the roadside and have multiple points of origin. The hot ceramic particles are discharged from the exhaust and resemble a honeycomb or small beads, as shown in Photos 3 and 4. Remember, when working close to the roadside, safety is our first concern. Follow local, state and federal guidelines while operating.

Lubricant and fuel: This type of fire is caused by fluid being ignited from a heat source and extends to wildland areas. The fuel fire can be caused by refueling or hydraulic lines leaking.

Friction: Friction is heat that is created by moving objects.

Radiant or conductive heat: Radiant or conductive heat transfer can be caused when vegetation is in contact with hot exhaust or engine surfaces. The investigator should identify any area of overgrown vegetation that a vehicle or equipment has been parked or is being stored on.

Mechanical breakdown: Mechanical breakdown is closely related to friction. The examples of mechanical breakdowns are transmission failure, electrical, brake and tire failure.

Miscellaneous Ignition Sources

The investigator may use miscellaneous ignition sources, however, you must be prepared to support and prove your findings. Some examples of miscellaneous causes are as follows; power lines, cutting and welding operations, firearms, spontaneous combustion, flares and fireworks. Let’s discuss some miscellaneous fire causes.