Firefighter Pre-Basic



  1. Introduction to Fire Behavior
    1. Fire is rapid oxidation accompanied by light and heat
    2. Combustion is a rapid chemical reaction that gives off energy or products that cause further reaction
    3. Products of combustion
      1. Smoke which contains carbon particles
      2. Heat - thermal and radiant
      3. Gases - carbon monoxide, carbon dioxide, hydrogen cyanide, water vapor
  2. Definitions
    1. Flash point - point at which there is sufficient fuel and oxygen vapors to form an ignitable mixture - gasoline has a flash point of =45oF
    2. Ignition temperature - point at which fuel vapors ignite automatically with sufficient oxygen - gasoline has an ignition temperature of 536oF
    3. Flammable range - range in which there is sufficient fuel vapors to form an ignitable mixture with oxygen - gasoline has a flammable range of 1.4% to 7.6% by volume mixed with air
    4. Specific gravity - weight of a liquid or solid in relation to an equal volume of water with water having a weight of one - gasoline has a specific gravity of 3 to 4
    5. Vapor density - weight of fuel vapor in relation to air with air having a weight of one - gasoline has a vapor density of .8
  3. Fire Tetrahedron
    1. Oxygen
      1. Air contains 21% oxygen
      2. At least 16% required to sustain life and combustion
      3. Also referred to as an oxidizer
    2. Fuel
      1. All fuels must be converted to vapor to burn
      2. Solid fuels convert to vapor through pyrolysis
      3. Liquid fuels convert to vapor through vaporization
      4. Gases already exist in vapor form
      5. Proportion of vapors must be in proper flammable range to burn
      6. Surface-to-mass ratio can affect how quickly something will ignite or burn (smaller materials ignite quicker but burn out quicker)
      7. Size and arrangement of fuel can affect the ability to ignite and burn (materials that are tightly packed are harder to ignite and burn)
      8. Fuel energy is measured in British thermal units or BTUs
    3. Heat
      1. Needed to produce vapor in solid or liquid fuels
      2. Sources of heat include mechanical processes, chemical reactions, electrical resistance, solar energy, and nuclear releases
      3. Heat is measured in degrees fahrenheit or celsius
    4. Self-sustained chemical reaction
      1. Fuel in a vapor state, an oxidizer, and heat energy come together in a very specific way
      2. Combustion can only continue when enough heat energy is produced to cause continued development of fuel vapors
  4. Methods of Heat Transfer
    1. Convection - transfer of heat through liquids or gases, including smoke
    2. Conduction - transfer of heat through solid surfaces such as metal pipes or ductwork
    3. Radiation - transfer of heat through electromagnetic waves which are absorbed by opaque surfaces
  5. Stages of Fire
    1. Ignition
      1. Point at which fire starts
      2. Ignition sources include matches, smoking materials, overheated electrical wiring or equipment, chemical reactions, solar heat
      3. Plenty of oxygen, little heat and smoke
      4. Fire is small and generally confined to the fuel first ignited
    2. Growth
      1. Heat and smoke levels increase
      2. Oxygen level decreases
      3. Fuel being dried out (cold smoldering)
      4. Hot gases rise to the ceiling and spread outward to the walls
      5. Continues if enough fuel and oxygen are available
      6. Fire is fuel controlled
    3. Flashover
      1. Transition between growth and fully developed stages and is not a specific event
      2. Plenty of heat and smoke which indicate rapidly changing conditions
      3. May involve all exposed combustibles
      4. Increasing levels of smoke with decreased visibility
      5. Gases generated are heated by radiant energy from the gas layer at the ceiling
    4. Fully developed
      1. All combustibles are involved in fire
      2. Maximum amount of heat being released
      3. Heat release and volume of fire dependent on number and size of ventilation openings
      4. Unburned fire gases begin flowing to adjacent spaces and ignite as they enter a space where air is more abundant
    5. Decay
      1. Intensity of fire decreasing due to lack of available fuel
      2. Most of fuel consumed
      3. Effort concentrated on cooling down remaining fuel
  6. Fire Extinguishment Theory
    1. Temperature reduction
      1. Using water to reduce temperature of fuel to a point where it does not produce sufficient vapors to burn
      2. Can be used on solids and liquids with high flash points
      3. Must be applied in sufficient quantity to absorb the heat being generated
    2. Fuel removal
      1. Accomplished by removal of fuel or by stopping flow of fuel
      2. Also accomplished by allowing fuel to be consumed
    3. Oxygen exclusion
      1. On small cooking stove fires, accomplished by placing a lid on the container
      2. Accomplished by flooding the area with an inert gas which is heavier than air such as carbon dioxide
      3. Blanketing the fuel with foam excludes oxygen
    4. Chemical reaction inhibition
      1. Accomplished using extinguishing agents such as dry chemical
      2. Effective on gas and liquid fuels
  7. Classes of Fuel
    1. Class A
      1. Ordinary combustibles such as wood, cloth, paper, rubber, and many plastics
      2. Water used to cool
    2. Class B
      1. Flammable and combustible liquids and gases such as gasoline, oil, lacquer, paint, mineral spirits, and alcohol
      2. Generally requires the use of special extinguishing agents such as foam
      3. Small fires can be extinguished with portable extinguishers
    3. Class C
      1. Energized electrical equipment such as household appliances, computers, transformers, and overhead transmission lines
      2. Requires use of non-conducting extinguishing agents such as dry chemical or carbon dioxide
    4. Class D
      1. Combustible metals such as aluminum, magnesium, titanium, zirconium, sodium, and potassium
      2. Requires special extinguishing agents for the material burning