Chapter Eighteen Part I– Fire Investigations

FRSC 8104Criminalistics II

Professor Bensley

FRSC 8104 – Chapter 18 ObjectivesAfter studying this chapter, the student should be able

to: Recognize the basic components required to have a

fire Understand how fire scene evidence is recognized,

collected, and analyzed

FRSC 8104 – Chapter 18 OutlineI. Fire Investigation Techniques - Introduction

A. Why not the word arson?B. Types of Fuel

1. Gases2. Liquids3. Solids

Simple Pyrolysis

FRSC 8104 – Chapter 18 OutlineII. Physical Properties of Fuels

A. FlammableB. CombustibleC. Flash Point

Flash Point Lab Apparatus

Flash Point of Butanol• Normal butanol has a flash point in a closed cup of 29°C. It is

therefore extremely flammable on a hot summer day when its

vapors come in contact with a flame or spark.

FRSC 8104 – Chapter 18 Outline

D. Flame PointE. Ignition Temperature

• Turpentine has an auto-ignition temperature of 253°C. Therefore, it will not burst into flame by itself at ambient temperature.

Video of Flash Point, Flame Point, Ignition Temperature

FRSC 8104 – Chapter 18 Outline

F. Explosive Limits• Ethylene has a lower explosive limit of 2.7% and an upper limit of 36%. Therefore,

in the presence of an ignition source, if the concentration of the gas is less than 2.7% or greater than 36%, there is no risk of explosion. But if the concentration of the substance is between these two limits, the mixture could explode. The concentration of the product in the air must be kept under its lower explosive

limit, for example by using appropriate ventilation.

FRSC 8104 – Chapter 18 Outline

G. Vapor DensityH. Heat of Combustion (Heat Output)I. Flashover

Flashover Videos:

Controlled Environment Flashover

http://abcnews.go.com/2020/video/arson-lab-tests-flashpoint-occurs-10590272

FRSC 8104 – Chapter 18 OutlineIII. Chemistry of Fire

A. Three basic reactionsB. Organic CompoundsC. Elements of combustion (Fire Triangle or Fire

Tetrahedron)

FRSC 8104 – Chapter 18 OutlineIV. Introduction to Petroleum Products

A. Light to Heavy ClassificationB. Classes (Types)

1. Natural Gas2. LP Gas3. Petroleum4. Gasoline5. Kerosene6. Diesel Fuel7. Fuel Oil8. Lubricating Oils

FRSC 8104 – Chapter 18 Outline

Fractional Distillation

Tower

FRSC 8104 – Chapter 18 OutlineV. At the Scene of a Fire (The Investigation)

A. Purposes of InvestigationsB. Types of Fires

1. Natural, Accidental, Deliberate (Incendiary)2. Classifying by Cause

a. Direct Ignitionb. Electricalc. Weather-Relatedd. Mechanical

FRSC 8104 – Chapter 18 Outline

C. General Principles of Fire BehaviorD. Fire Behavior Indicators

1. Burn Patterns

Another Classic V-Pattern

The pattern is typical of an overheated appliance on the kitchen countertop. The arrow points to severely burned wallboard at the base of the V-pattern where a decomposed, plastic coffee pot housing was found, the apparent cause of the fire.

FRSC 8104 – Chapter 18 Outline2. Heat Level (Heat Horizon)3. Smoke Level (Smoke Horizon)4. Low Burns5. Spalling

6. Glass

1000 mL Gasoline on Parquet Floor

1000 mL Gasoline on Vinyl Floor

1000 mL Kerosene on Parquet Floor

FRSC 8104 – Chapter 18 OutlineE. Evidence Collection

FRSC 8104 – Chapter 18 OutlineVI. Laboratory Analysis

A. Extraction Methods1. Solvent Extraction2. Headspace

FRSC 8104 – Chapter 18 Outline3. Steam Distillation4. Purge and Trap (Charcoal Tube)5. Passive Headspace Diffusion (Charcoal Strips)

Purge and Trap Schematic

FRSC 8104 – Chapter 18 OutlineB. Analytical Techniques

1. FTIR (Rare)2. TLC for dyes3. UV-Vis (Rare)4. GC/FID5. GC/MS

a. GC/MS/MS

Gasoline Chromatogram

Weathered Gasoline

BTEX in Gasoline

Gasoline Chromatogram

Diesel Fuel Chromatogram

FRSC 8104 – Chapter 18 OutlineVII.ASTM Classification System (2002)

A. ASTM E-16181. Gasoline2. Petroleum Distillates3. Isoparaffinic Products4. Aromatic Products5. Napthenic paraffinic products6. n-Alkanes7. De-aromatized Distillates8. Oxygenated Solvents9. Others – Misc.

FRSC 8104 – Chapter 18 OutlineVIII.MS Characteristic

PeaksA. Pristane and

PhytaneB. Other CompoundsC. Gasoline Target

Compounds