Fire Definition and Components

Fire: Definition and Components

• Fire is a rapid chemical reaction between fuel and an oxidizer (usually oxygen).
• This reaction releases energy in the form of heat and light.
• Light appears as a flame, a glowing mass of burning material and luminous gases.
• Pyrolysis is the decomposition of matter by heat, converting solid fuel to vapor.
• Combustion is a self-sustaining reaction that produces energy and more reactants.

Fire Triangle and Tetrahedron

• Fire needs three elements: fuel, oxygen, and heat.
• The Fire Triangle visualizes these elements.
• The Fire Tetrahedron adds a fourth element: chain reaction. This sustains the fire.
• Removing any element extinguishes the fire.

Combustion Products

• Fire gases are what remain after combustion has cooled.
• Flames are incandescent burning gases showing various colors.
• Heat is a form of energy measured in temperature.
• Smoke is a visible sign of incomplete combustion, mostly a mixture of gases and particles (soot, carbon).

Spontaneous Combustion

• Spontaneous combustion arises from heat generated by an internal chemical process.

Fuel Properties

• Fuel exists in solid, liquid, and gas form (varying molecular packing).
• Physical properties include specific gravity, vapor density, vapor pressure, temperature, boiling point, ignition/kindling temperature, fire point, and flash point.
• Ignition point is the minimum temperature needed for combustion.
• Free radicals are combustible vapors produced at high temperatures during pyrolysis.

Chemistry of Fire

• Endothermic reactions absorb heat.
• Exothermic reactions release heat (ex: combustion).
• Oxidation is a chemical change where fuel and oxidizer react.
• Combustion is rapid oxidation.

Flame Types

• Luminous flames are orange-red, incomplete combustion, producing soot, and having lower temperatures.
• Non-luminous flames are blue, complete combustion, having higher temperatures.
• Premixed flames (e.g., Bunsen burner) involve mixing fuel and air before ignition.
• Diffusion flames (e.g., candle) occur when fuel diffuses into air.
• Laminar flames have smooth paths, and turbulent flames have irregular flows.

Fire Elements

• The elements of fire are fuel, heat, and oxygen, along with chain reaction in flaming combustion.

Fuel Classification

• Fuels are classified as solid, liquid, or gas, each with unique properties.
• Common fuel types include wood, plastics, flammable liquids (like oil), and metals (magnesium, titanium).

Extinguishing Fire

• Extinguishing methods vary based on the fuel type (class).
• Class A: Water.
• Class B: Smothering agents (carbon dioxide, dry chemical powder).
• Class C: Non-conductive agents (carbon dioxide, dry chemical powder).
• Class D: Special dry powders for metals.
• Class K: Wet chemical agents for cooking oils.