Tactical firefighting Flashcards
What is an atom?
Protons, neutrons and electrons form an
atom.
Electrons carry a negative electrical charge; Protons carry a positive electrical charge;
Neutrons do not have an electrical charge
Wahr the 3 states of matter?
- Solid e.g. wood, coal, rubber
- Liquid e.g. petrol, oil, paints
- Gas e.g. methane, nitrogen, oxygen
What is combustion?
Combustion is a chemical reaction that occurs between a fuel (e.g. hydrocarbon) and an oxidising agent (e.g. oxygen) that produces energy, usually in the form of heat and light/glow
4 stages of combustion
- Incipient Stage: Invisible products of combustion given off. No visible smoke, flame or appreciable heat is present yet.
- Smouldering Stage: Combustion products now visible as smoke. Flame or
appreciable heat is still not present. - Flame Stage: Actual fire now exists. Appreciable heat is still not present but follows almost instantaneously.
- Heat Stage: Uncontrolled heat and rapidly expanding air now complete the dangerous combination. The considerable heat is transferred to the atmosphere and nearby matter.
What is fire?
Fire is the rapid combination of oxygen with fuel in the presence of heat, typically characterised by flame, a body of incandescent gas that contains and sustains the reaction and emits light and heat.
Fire triangle
- Oxygen
- Heat
- Fuel
The Fire Tetrahedron
- Oxygen
- Heat
- Fuel
- Chemical chain reaction (in between)
Flame types
Diffused Flame (Yellow)
In a diffused flame, combustion with
volatiles takes place at the flame surface
only, where the fuel /oxygen ratio is at its
optimum.
Premixed Flame (Blue)
In a premixed flame, gas or vapour is able to mix with oxygen and provide a mixture
within the flammability limits.
What is complete combustion?
During complete combustion, sufficient oxygen and heat are available to consume all the available fuel, resulting in the release of water vapour (H2O), carbon dioxide (CO2), and nitrogen oxides (NOx).
What is incomplete combustion
Incomplete combustion occurs when the supply of air or oxygen is limited, preventing the complete oxidation of the fuel. By-products of incomplete combustion include water vapour (H2O), carbon dioxide (CO2), nitrogen oxides (NOx) carbon monoxide (CO), smoke (soot or carbon)
What is flammable range
Flammable range is the range in which a gas or vapour concentration (percentage by
volume in air) will burn or explode if an ignition source is present
What is pyrolysis?
Scientifically, pyrolysis is defined as the chemical breakdown of an organic substance by heat, in the absence of oxygen.
In firefighter terms, pyrolysis is the decomposition of a substance through application of heat.
If a solid or liquid substance is heated, gases will be given off.
