Fire Behavior Flashcards
Heat vs. Smoke
- Heat is energy
- Smoke is fuel
Fire
Complex chemical reaction that converts one combination of substances into different combinations of substances and releases energy in the form of heat and light.
Mechanical Energy
Friction
Electrical Energy
- Electricity produces heat when it flows through a wire or any other conductive material
- The greater the flow of electricity and the greater the resistance of material, the greater the amount of heat produced
Fire Tetrahedron
- Fuel
- Oxygen
- Heat
- Sustained Chemical Chain Reaction
Heat Release Rate
Speed at which energy is released
Oxidation
Process in which oxygen combines chemically with another substance to create a new compound
Combustion
Rapid chemical process in which the combination of a substance with oxygen produces heat and light
Three Major Components of Smoke
- Particles (solids)
- Vapors (finely suspended liquids/aerosols)
- Gases
Methods of Extinguishment
- Cool the burning material
- Exclude oxygen
- Remove fuel
- Interrupt the chemical reaction
Class A/B/C/D/K
- A: Ordinary combustibles
- B: Flammable or combustible liquids and/or gases
- C: Energized electrical equipment
- D: Combustible metals
- K: combustible cooking oils and fats in kitchens
Class B:
Flammable or combustible liquids and/or gases
4 Stages of Solid-Fuel Fire Development
-Ignition
-Growth
(Flashover)
-Fully Developed
-Decay
Flameover (Rollover)
-Flaming ignition of how gases that are layered in a developing room or compartment fire (flames in the smoke)
Thermal layering
-Gases rise as they are heated and form layers within a room
Backdraft
An explosion after a closed box with a limited supply of oxygen and superheated gases is suddenly exposed to ocygen.
Signs of Backdraft
- Confined fire with a large heat build-up
- Little visible flame from the exterior of the building
- “Living fire” smoke puffing from the building, as if it is breathing
- Smoke that seems pressurized
- Smoke-stained windows (indication of significant fire)
- Turbulent smoke
- Ugly yellowish smoke (containing sulfur compounds)
Mixed compound liquid fuels flammability determined by:
Compound with the lowest ignition temperature
Flash Point
Lowest temperature at which a liquid produces a flammable vapor
Flame Point (Fire Point)
Lowest temperature at which a liquid produces enough vapor to sustain a continuous fire
Vapor Density
- Air = 1
- Vapors < 1 Rise and dissipate
- Vapors > 1 Sink
Lower Flammable Limit
Minimum amount of gaseous fuel that must be present in a gas-air mixture for the mixture to be flammable
BLEVE
B oiling L iquid E xpanding V apor E xplosion
-To prevent, cool top of container
Ventilation Controlled Fire
Ignites, grows, consumes all oxygen and decays, until oxygen is introduced and room flashes.
Ignition Temperature
-Minimum temperature at which a fuel, when heated, will combine with air and continue to burn
