How are fire causes investigated?

Fire investigation is a complex and specialized discipline that shares similarities with forensic crime investigation but is distinguished by its unique challenges and dangers. This discipline requires deep knowledge of fire science and meticulous attention to detail to identify the origin and cause of fires. Below is a detailed and enriched analysis of this topic, divided into several sections for ease of understanding.

Fire investigation begins once the firefighters have extinguished the flames. Like a crime scene, it is crucial to preserve the site and collect and analyze evidence, although this is done under much more difficult and dangerous conditions. The goal is to meticulously examine the damaged scene to determine where and how the fire started, and ultimately establish its cause.

Fundamentals of Fire Chemistry and Behavior

Chemical Nature of Fire

Fire results from an exothermic combustion reaction, releasing heat and light. For a fire to occur, three components are essential: a fuel, an oxidant (usually oxygen), and sufficient thermal energy. These elements form the “fire triangle.” Additionally, for a sustained reaction, a chemical chain reaction is required, adding a fourth element, creating the “fire tetrahedron.” The disruption of any of these elements can extinguish a fire.

Pyrolysis Process and Fire Behavior

Pyrolysis occurs when solid and liquid materials are heated to produce flammable vapors. This process is critical in combustion and can be influenced by the nature of the material. The color of the flames can vary depending on the material involved in the combustion, indicating different temperatures and substances burned.

Heat Propagation

The heat generated by a fire can spread in three main ways: convection, conduction, and radiation. Each method has unique characteristics and plays a crucial role in the dynamics and expansion of the fire.

Ignition and Its Mechanisms

Ignition occurs when all necessary conditions are met to start a fire. Ignition sources can vary, including chemical reactions, friction, solar radiation, and electricity. Critical temperatures, such as the flash point and the auto-ignition point, are fundamental to understanding different types of ignition.

Types of Fire

Smoldering Fire and Flameless Combustion

Not all fires produce visible flames. A smoldering fire can occur in materials such as cellulose, creating a solid char and releasing thick smoke. These fires can be especially dangerous due to their ability to burn for extended periods without detection.

Spontaneous Combustion

This phenomenon occurs when a material ignites without an external ignition source, often due to internal chemical reactions generating enough heat to start a fire.

Examination and Analysis of the Fire Scene

Safety and Risk Assessment

Before beginning the investigation, it is crucial to conduct a dynamic risk assessment to ensure that the scene is safe for investigators and other professionals.

Collection of Testimonies

Witnesses can provide valuable information about conditions prior to the fire and suspicious activities observed. However, the reliability of witnesses must be carefully evaluated.

Documentation and Analysis of the Scene

The fire site must be treated with the same rigor as a crime scene, meticulously documenting all evidence and observations. This includes creating a detailed plan of the site and a thorough examination of all entries and potential ignition sources.

Specific Investigation of Arson

Summary of Specific Investigation of Arson

Arson investigations are crucial when a fire is suspected to have been set intentionally. These investigations require a specialized approach due to the potential involvement of criminal intent. The primary focus is to determine whether the fire was accidental, natural, or deliberate. Here are the key components of an arson investigation:

  1. Evidence Collection: Collecting evidence at an arson scene involves rigorous methods similar to those used in other crime scene investigations. This includes documenting burn patterns, the presence of accelerants, and any tools or devices that could have been used to start the fire.
  2. Analysis of Burn Patterns: Burn patterns provide crucial clues in arson investigations. Investigators look for localized burning, signs of accelerants, and multiple points of origin, which are often indicative of arson.
  3. Accelerants Detection: The presence of accelerants is a strong indicator of arson. Investigators use dogs trained to detect hydrocarbons or sophisticated equipment such as gas chromatographs to identify traces of flammable liquids.
  4. Interviews and Motive Exploration: Understanding the motives behind suspected arson is essential. Interviews with property owners, occupants, and witnesses can provide insights into potential motives such as insurance fraud, revenge, or covering up another crime.
  5. Scene Reconstruction: Arson investigators often reconstruct the scene to understand how the fire started and spread. This involves analyzing the damage and the materials involved to establish the fire’s origin and progression.
  6. Interdisciplinary Collaboration: Arson investigation is typically a collaborative effort involving fire investigators, law enforcement, forensic experts, and sometimes psychologists, especially when profiling suspected arsonists.

The goal of arson investigation is not only to determine if a fire was set intentionally but also to gather sufficient evidence for prosecution if a criminal act is confirmed. This meticulous approach ensures that all technical aspects are considered and the true cause of the fire is accurately identified.


Fire investigation is a meticulous science that requires a deep understanding of multiple disciplines. From understanding the chemistry of fire to analyzing burn patterns and gathering testimonies, each step is vital for uncovering the truth behind a fire.

Daeid, N N, 2005. Fire Investigation. Florida: CRC Press.
Fairgrieve, S I, 2008. Forensic Cremation: Recovery & Analysis. Florida: Taylor & Francis Group.
TC Forensics. [online] Available at: [
Fire Investigation. (s/f). Recuperado el 9 de noviembre de 2021, de