Course Learning Outcomes for Unit IV
Upon completion of this unit, students should be able to:
1. Explain the physical and chemical properties of fire.
1.1 Define the categorization of flames.
1.2 Describe laminar and turbulent flames
1.3 Categorize the flash point, fire point, and autoignition temperature of a flammable liquid.
4. Describe and apply the process of burning.
4.1 Compare the flammability limits of burning velocity.
4.2 Evaluate the three zones of the plume of a fire burning in the relationship of air entrainment into
the flame.
5. Define and use basic terms and concepts associated with the chemistry and dynamics
5.1 Analyze the minimum rate of heat release that leads to a flashover.
5.2 Compare the smoke flow through different types of buildings.
Reading Assignment
Chapter 7:
Fire Characteristics: Gaseous Combustibles
Chapter 8:
Fire Characteristics: Liquid Combustibles
Chapter 12:
Movement of Fire Gases
Unit Lesson
Understanding the flame phenomena is critical for the safety of firefighters. However, is it important to
understand diffusion of flame spread across a combustible item? How does that relate to firefighters making
entry into a structure? Why is it important to understand the categorization of flames from Bunsen burners,
Porous-plate flat-flame burners, or any other type of burner using natural gas or liquefied petroleum gas? Why
is it important to understand fuel being diffused with air? Shackelford (2009) stated, “The diffusive flaming
process is characterized by flames, generally yellow in nature as the burning process is not complete” (p. 58).
According to Shackelford the appearance is as though the fuel to air ratio is incorrect. He claimed, “It is the
most common type of flaming that will be encountered by firefighters” (p. 58) and the yellow flame suggests
carbon monoxide being formed. Corbett and Pharr (2011) support Shackelford, suggesting the color of the
flame is characterized by the percentage of oxygen available for combustion and fuel composition. Will the
entrainment of more air into the flame improve combustion? Is there another element that needs to be
considered?
Gann and Friedman (2015) state that, for combustion to occur, the air mixture and the fuel mixture must be
within the flammable limits range of the material involved, which is indicated by the change in flame color. The
authors continue by saying, “Flame types fall into the following categories: Premixed flames or diffusion
flames; laminar flames or turbulent flames; stationary flames or propagating flames; subsonic flames
(deflagrations) or supersonic flames (detonations)” (p. 96). The authors suggest there are other possible
combinations of these categories. McCaffery (1979) claimed buoyancy diffusion flame as another type. He
stated that buoyancy diffusion flame propagation is viewed as intermittent velocity of the plume or fluctuating
UNIT IV STUDY GUIDE
Physical and Chemical
Properties of Fire