scientific method approach

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Course Learning Outcomes for Unit I Upon completion of this unit, students should be able to:

4. Summarize the scientific method used to complete a fire investigation. 4.1 Describe each step of the scientific method. 4.2 Illustrate the ways fire investigators can use the scientific method within a fire investigation.

Course/Unit Learning Outcomes

Learning Activity

4.1

Unit Lesson Chapter 1 Chapter 2 Unit I Essay

4.2

Unit Lesson Chapter 1 Chapter 2 Unit I Essay

Required Unit Resources Chapter 1: Fire and Science Chapter 2: The Chemistry and Physics of Combustion

Unit Lesson Fire and Science Today’s fire investigations have truly changed for fire officials and investigators. Through the usage of the scientific method approach, located in National Fire Protection Association (NFPA) 921, the fire investigator utilizes a hypothesis-driven method for validating the cause and origin of fires. Advances over the past 40 years have provided major changes in understanding fire dynamics and behavior. Through mathematical

equations, fire modeling, and recreating various phases of a fire, investigators can validate how a fire was started and spread throughout a structure. The textbook author describes the scientific method approach as a way of thinking that provides a set of techniques for testing the validity of human ideas (Lentini, 2019). The scientific method approach reveals not only the study of fire, but also the method in which fires were started and maintained. This mindset creates a scientific approach not just in the laboratory but also on the fireground. The wide-spread concept of consensus and fire-cause determination has moved toward this science but based on consensus with the combination of both scientific application, knowledge, and experience by the fire investigator.

UNIT I STUDY GUIDE

General Fire Science

Hypothesis of fire investigation (Ctitze, n.d.)

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Helpful Resources The NFPA 921 guide for fire and explosive investigations was produced with the intent of improving fire investigations and processes. Some fire investigators believe that NFPA 921 is one of the most important documents, as it contains new technology and advancements in conducting fire investigations on fire behavior and has been accepted throughout the investigation community that includes fire officials, the insurance industry, and engineering and other scientific professions abroad. You are highly encouraged to become part of the local, state, and international associations of fire investigators. The International Association Arson Investigators (IAAI) has a wealth of information related to fire investigations. With the creation of the Certified Fire Investigator Trainer (CFITrainer.net), fire investigators have a web-based learning tool to increase knowledge through online training modules with subject matters that include various case studies; arc mapping; basic electricity; processing the fire scene through documentation, sketching, photography, interviews and critical thinking; and problem-solving pertaining to fire investigations. Another document that is available is the NFPA 1033: Standard for Professional Qualifications for Fire Investigator, which provides the minimum standards of knowledge and skills related to fire science, fire chemistry, fire dynamics, computer modeling, as well as fire investigation techniques. It is through NFPA 1033, certifications and recognition for fire investigators are established and maintained for a practicing fire investigator. As a fire investigator, you must learn the value placed upon an investigation that involves many components in developing a hypothesis and validating it. Not only experience but knowledge, training, and practical application, along with a professional certification representing NFPA 1033 and through the usage of NFPA 921 can a fire investigator begin to be considered as a subject matter expert in the field of cause and origin investigation. In addition, agencies such as Underwriters Laboratories (UL) and National Institute of Standards and Technology (NIST) have assisted in validating futuristic research used in fire modeling within controlled environments that recreate the fire scene and its cause. These case studies have been found to be very reliable when paired with scientific method approach in validating the cause and origin, the spread of fire, as well as the cause of injury or death of a firefighter or citizen. NFPA 921 - Scientific Method Approach The basic methodology of any fire investigation should demonstrate a systematic approach along with relevant details concerning the fire. This is done through the systematic approach found in NFPA 921—known as the scientific method approach for fire investigations. The step-by-step analogy is used to uncover factual data concerning a fire or explosion. The investigation procedures are focused on first determining and establishing the origin of the fire. Once established, the investigation then centers around the circumstances, conditions, ignition source, and type of fuel used to create the fire. The scientific method approach utilizes a series of steps that assists in recognizing the need for investigation, defining the problem, collecting the data, analyzing the data, developing a hypothesis through inductive reasoning, testing the hypothesis through deductive reasoning, and then, selecting the validated hypothesis (Lentini, 2019). The scientific method approach is the fire investigators, law enforcement, and court attorneys have accepted as a

Steps of the scientific method approach (Lentini, 2019)

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standardization in conducting fire investigations for determining the various classes of fires. These include accidental, incendiary, natural, as well as undetermined. Through this type of a systematic approach, a standardization has been developed and implemented for conducting fire investigations. This systematic approach has been proven to be reliable and is validated in determining the cause and origin of fires. Chemistry and Physics of Combustion Firefighters and fire investigators must have a common knowledge of fire dynamics describing the exothermic chemical reaction that produces energy. Fire is defined by many as the rapid oxidation process utilizing the evolution of heat, fuel, and a chemical chain reaction (Lentini, 2019). Known as the fire tetrahedron, this chain reaction creates the phenomenon known as a fire. These reactions produce measurable energy known as the joule (J). The rate at which energy is released is known as power and is measured within a joule per second or watts (W). The manpower transmitted to a given area is also called heat flux and is measured in kilowatts per square meter or watts per square centimeter. Most single properties of a fire involve the heat release rate (HRR); through this process the fire investigator is able to determine how the fire will spread throughout a structure. The HRR of a fire is measured in kilowatts to show the size of a fire. HRR is the single most important property of the fire that allows the fire investigator to determine how the fire will behave through the decomposition of matter along with the fire investigator’s knowledge of exposure to the various stages of fire. As a fire investigator, you should examine the HRR that may be produced at various temperatures, which depends upon the fire’s ability to draw in fresh air (oxygen) within the fire plume. The HRR determines the temperature within a fire and its destruction, especially in and around the area of the fire plume which intensifies or decreases in temperature as it moves toward the decay phase, which is characterized by a significant decrease in oxygen or fuel. Matter within itself is composed of atoms, which are made of compounds known as molecules. These molecules are made up of two or more atoms held together by chemical bonds creating solids are known as polymers, consisting of long chains of repeated units called monomers. Fire investigators must also have a clear understanding of flammable limits or concentration of the fuel/air mixture. Gases that are too lean are known as the lower flammable limit and/or lower explosive limit. This is signified by LEL. The fuel/air mixture that is too rich in concentration is known as the upper flammable limit, upper explosive limit or UEL. As a fire investigator, it is extremely important to have a general knowledge of ordinary matter that is broken down into three categories: solids, liquids, and gases. Gases will burn when present at concentrations within flammable limits and exposed to ignition sources such as pilot lights and open flame. Liquids and solids must be transformed into gases that are vaporized or decomposed in order for a fire to ignite and burn. Combustion continues as long as the flames radiate enough energy to cause continuing production of both vapors and gases within the atmosphere.

States of matter (Julesunlimited, n.d.)

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Fire Dynamics and Fire Pattern Development Ignition is the process that causes self-sustained combustion. Vapors or dust clouds are more easily ignited than solids (Lentini, 2019). A flame is a luminous volume where combustion occurs. Flames can be either premixed or diffused, laminar, or turbulent in nature. Flammability makes ignition occur and determines the rate of fire spread, HRR, along with the other reactions in relationship to fire behavior and the various types of fuels. Self-heating or spontaneous ignition is the result of an exothermic reaction that is created by some materials under certain conditions where heat increases to a temperature that self-ignites material. One of the more common causes of spontaneous ignition is related to shop rags and the use of linseed oil used on hardwood floors, and HTH—chlorine chemical reactions. Many times, fire investigators are summoned to investigate smoldering fires that may include discarded cigarettes, matches, couches, or bed mattresses all of which could be classified as the four most common types of fires: accidental, incendiary, natural, as well as undetermined. Understanding the characteristics of flames is also very important when conducting fire investigations. The flame known as diffusion flame is very important in physical evidence that assists in measuring the concentration level of fuel vapors and oxygen. Many types of substances found within structures when ignited become diffused from areas of high concentration of vapors to lower concentrations. This can be signified by the various burn patterns that will be introduced in this course. Common appearances such as the line of demarcation, V patterns, cone patterns, and the depth of charring will all provide physical prints of how the fire progressed throughout the various stages of a fire as the investigator works through the least to the greatest damaged areas. A significant part of evidence is determining the flashpoint. The term flashpoint signifies the lowest temperature of a liquid as determined by laboratory testing for which the liquid gives off vapors at significant rate to support flame production. This process can assist fire investigators in determining the movement of the fire as it progressed through the various surfaces of combustible material known as flame spread. Flame spread can move throughout structures by various means such as convection, conduction, and radiant heat in direct contact with the flame. Compartment fires behave a little differently than the free burning fires that most firefighters are familiar with within their profession. A fire investigator must learn the application of NFPA 921, the scientific method approach that provides seven components in validating pre- and post-flashover burning phases, along with the mechanics associated with burn patterns that are developed and interpreted. These equations and models enhance the understanding of a fire within a building that brings together the hypothesis and its validation for what caused the fire initially. The fire investigator should take his or her time investigating fires by working from the least to the most

damaged areas. Conduct a 360 walk around visualizing the various ventilation openings in which the fire ventilated itself as it progressed and consumed the contents of the structure. Fire patterns within the structure signify the measurable effects of the fire itself. These fire patterns are recorded on the surfaces such as in the case of direct flame impingement. The interpretation of these burn patterns such as the V-shaped fire plume is a geometric signature typically at the base of the wall moving upward in V-pattern. In the case of the inverted cone that is the overlay of another fire plume. Firefighters should take the opportunity to look very closely at the various ventilation points that are created when the fire moves from one room to another. This rounded semicircular pattern provides the direction of travel as it moves throughout the structure. Fire modeling, such as smoke view simulator, provides excellent illustration of heat flux and thermal buildup as the fire intensifies as fuel and oxygen accelerate the fire plume both in size and configuration. Summary For the fire investigator, there are many aspects that require knowledge, training, and practical application in determining the cause and origin of a fire. The utilization of NFPA 921, scientific method approach, and NFPA 1033 help to provide the minimum standards for becoming a fire investigator. Chapters 1–3 of our course

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textbook provide a brief overview of basic history, chemistry, and fire dynamics for creating an understanding of how to conduct a fire investigation through accepted methods adopted by the fire investigation profession.

References Ctitze. (n.d.). Hypothesis (ID 87920188) [Illustration]. Retrieved from

https://www.dreamstime.com/hypothesis-glowing-neon-sign-stonework-wall-d-rendered-royalty-free- stock-illustration-can-be-used-online-banner-ads-image87920188

Julesunlimited. (n.d.). States of matter and transitions (ID 23864963) [Illustration]. Retrieved from

https://www.dreamstime.com/stock-photos-states-matter-transitions-image23864963 Lentini, J. J. (2019). Scientific protocols for fire investigation (3rd ed.). Boca Raton, FL: CRC Press.

Suggested Unit Resources In order to access the following resources, click the links below. The chapter presentations below include review questions from the chapters: Chapter 1 Review Presentation (PowerPoint) Chapter 1 Review Presentation (PDF) Chapter 2 Review Presentation (PowerPoint) Chapter 2 Review Presentation (PDF) This suggested reading discusses the use of the scientific method in examining the area of origin and the cause of a fire. Herrera, F. (2006). First responder fire investigations. Firehouse, 31(2), 62–67. Retrieved from

https://libraryresources.columbiasouthern.edu/login?url=http://search.ebscohost.com/login.aspx?direc t=true&db=bcr&AN=20590935&site=ehost-live&scope=site

For those of you within the criminal justice field, you may find the following video interesting. The video explores the fires caused by outdated technology due to BP’s neglect. Frontline (Producer). (2010). Fires caused by outdated technology (Segment 2 of 21) [Video File]. Retrieved

from https://libraryresources.columbiasouthern.edu/login?auth=CAS&url=http://fod.infobase.com/PortalPla ylists.aspx?wID=273866&xtid=56057&loid=229143

The transcript for this video can be found by clicking on “Transcript” in the gray bar at the top of the video in the Films on Demand database.

Learning Activities (Nongraded) Nongraded Learning Activities are provided to aid students in their course of study. You do not have to submit them. If you have questions, contact your instructor for further guidance and information. Nongraded Activity #1: If you were to hire a fire investigator, what skills would you look for in a candidate? Consider how you would prepare a job description for a fire investigator utilizing NFPA 1033.

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Nongraded Activity #2: Brainstorm the ways the scientific method approach compares to the traditional methods used by fire investigators, such as experience over science.