Archive for February, 2012

by: Jason A. Sutula

Due to the ever increasing size of this post while writing, this topic will be divided into two posts!

Part I

“Amateurs hope, professionals work.” – Garson Kanin

All of the various paths, training, and educational opportunities discussed in my last post are intended to provide aspiring fire investigators with a base level of understanding in certain topics that comprise fire investigation. These topics are outlined in NFPA 1033 – Standard for Professional Qualifications for Fire Investigator and are:

  1. Fire Science
  2. Fire Chemistry
  3. Thermodynamics
  4. Thermometry
  5. Fire Dynamics
  6. Explosion Dynamics
  7. Computer Fire Modeling
  8. Fire Investigation
  9. Fire Analysis
  10. Fire Investigation Methodology
  11. Fire Investigation Technology
  12. Hazardous Materials
  13. Failure Analysis and Analytical Tools (List from Section 1.3.8 of the 2009 NFPA 1033)

Section 1.3.8 of the 2009 edition of NFPA 1033 states that an “investigator shall have and maintain at a minimum an up-to-date basic knowledge of the following topics beyond the high school level at a post-secondary education level.” What is meant by “basic knowledge” can be a debatable point within the field, but overall the list accurately reflects the areas within which a fire investigator must be proficient in order to do his/her job correctly.

The definitions for the topics found in the above list come from another NFPA document: NFPA 921 Guide for Fire and Explosion Investigations. NFPA 921 is a very useful document that will be explored more fully in a separate post.

From the 2011 NFPA 921 (i.e., and all subsequent definitions will be from this published document unless otherwise noted), Fire Science is defined as, “The body of knowledge concerning the study of fire and related subjects (such as combustion, flame, products of combustion, heat release, heat transfer, fire and explosion chemistry, fire and explosion dynamics, thermodynamics, kinetics, fluid mechanics, fire safety) and their interaction with people, structures, and the environment.” The first definition listed is fairly broad and includes cross references to other topics already in our base-knowledge list. Some web-related definitions of fire science include fire department operations and organization for fighting fires. This is not what is meant by fire science when pertaining to fire investigators.

Fire Chemistry is not defined specifically in NFPA 921. Chemistry is also not defined, but Fire is defined, at least, as, “A rapid oxidation process, which is a chemical reaction resulting in the evolution of light and heat in varying intensities.” Fire is chemistry in action and chemistry encompasses all reactions that produce fire. The main point is that a basic understanding of how fuel (e.g., wood) and oxidizer (e.g., air) come together to produce different products of combustion, light, and heat is necessary to have any hope of correctly conducting a fire origin and cause investigation.

Thermodynamics is also not defined specifically in NFPA 921, but does represent the standard topic as found in college-level curriculum. Thermodynamics provides a systematic way to approach the concept of heat and how it can be related to energy and work. It is a building block topic necessary to understand how fire will interact with its surroundings.

Thermometry is also not defined in NFPA 921. Thermometry is a related topic to heat transfer and thermodynamics, with the focus of relating how temperature can be measured with various devices such as thermometers and thermocouples. All of the concepts necessary to understand how these devices work can be found within standard texts on heat transfer.

Within NFPA 921, Fire Dynamics is defined as, “The detailed study of how chemistry, fire science, and the engineering disciplines of fluid mechanics and heat transfer interact to influence fire behavior.” The main difference between fire science and fire dynamics is that a basic understanding of fire science is needed before an individual can accurately assess how a fire will interact with its surroundings. For example, by learning basic fire science a fire investigator will learn that fire is a chemical process (i.e., Fire Chemistry) between a fuel and oxidizer. Fire dynamics, on the other hand, allows for a deeper understanding of how the fire will spread over the surface of that wood and what the influence of wind, radiation, etc. will be on the spread rate of the flame. Scientific research into the behavior of fire is a very active branch of investigation and many of these very concepts in fire dynamics are being actively explored to raise our level of understanding.

While also not specifically defined in NFPA 921, Explosion Dynamics can be thought of in similar terms to Fire Dynamics. The main difference, of course, is that the physical processes that are covered under this topic all involve explosions. A explosion is defined in NFPA 921 as, “The sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure. These high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials.”

Computer Fire Modeling is actually one of my specialties within the field. The term is fairly general and can be used to describe a range of tools where a computer is used to calculate some parameter related to fire physics. For instance, this can be as simple as the use of computer spreadsheet filled with a single equation for the determination of the flame height above a pool fire to an extremely complex model designed to fully reconstruct a fire within an entire residence or industrial facility using a Computational Fluid Dynamics (CFD) code such as the Fire Dynamics Simulator (FDS).

Returning our attention to NFPA 921, Fire Investigation is simply defined as, “The process of determining the origin, cause, and development of a fire or explosion.” It sounds easy when it is defined so simply, but when cast in the light of all of the topics listed above that a fire investigator needs to be knowledgeable in, it becomes apparent that fire investigation is anything but simple.

NFPA 921 defines Fire Analysis as, “The process of determining the origin, cause, development, responsibility, and, when required, a failure analysis of a fire or explosion.” This definition reads identically to the definition of fire investigation with an extension added relating to determining the responsible party for the fire and potentially conducting a failure analysis.

Part II of this post will continue with the remaining points in our topic list and finish with a discussion on the certification process in fire investigation.

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