lesson 8

• Combustion or Burning

  • a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.
• Combustion Vs. Burning

  • The basic difference is that combustion is heating and no flames are produced whereas in burning most of the energy is converted to light energy and this results in less heat energy as compared to combustion. 
• Oxidation

  • Oxygen + Other Substances
• Ingredients of Fire

  • Heat
  • Oxidizing agent
  • Uninhibited chemical reaction
  • Fuel
• Heat

  • Energy
  • Must be enough to vaporize solid and liquid forms of fuel and cause ignition
• Conduction

  • direct contact
• Convection

  • flow of liquids and gasses
• Radiation

  • electromagnetic waves
• Oxidizing

  • an element or a compound which releases oxygen or other oxidizers during a chemical reaction
  • supports combustion when combined with a fuel
  • bromine, chlorine, fluorine, iodine, nitric acid, nitrites, perchlorates, peroxides, permanganates
• Uninhibited Chemical Chain Reaction

  • heat given off during combustion is used again to heat the fuel and maintain the burning
• Stages of Fire

  1. Ignition
  2. Growth
  3. Fully Developed
  4. Decay
• Ignition (Incipient)

  • The incipient stage is when it’s crucial to fight a fire because it is easiest to suppress it at this point, and it will cause the least damage. 
  • Theignition stage is when all four elements of the fire tetrahedron coalesce, the fuels reach their ignition temperature, and the fire begins
• Growth

  • the fire increases fuel consumption and creates more heat and smoke.
• Fully developed

  • the maximum amount of fuel and oxidizers are consumed, and the highest heat release rate is produced. 
• Decay

  • The temperature decreases and intensity is reduced during the decay stage, which happens when the available fuel has been consumed.
• Wildfire

  • Natural or Anthropogenic-caused
  • Uncontrolled fire in remote areas where there is extensive combustible
  • Vegetation and/or organic material like forests, grasslands, shrub lands, etc.
• Types of Wildfires

  1. Ground Fires
  2. Surface Fires
  3. Crown Fires
  4. Accidental Fires
• Ground Fires

  • Ground fires – also known as ‘subsurface fires’ – can occur in areas with large accumulations of dead vegetation over time, such as humus and peat. They move slowly beneath the surface terrain, making them difficult to see from above. 
• Surface Fires

  • They burn detritus such as litter, twigs, and leaves, which sit on the surface of the ground. They can also consume surface vegetation, such as shrubs and grasses.
• Crown Fires

  • A crown fire, which burns in the tree canopy, is the most dangerous type of wildfire. It burns extremely hot, and often spreads rapidly through the interconnected branches of trees.
• Causes of Building Fires

  1. Unattended cooking equipments and other household fire sources
  2. Electrical appliances and wiring problems
  3. Haphazardly stored flammable liquids and other easily combustible materials
  4. Firecrackers
• Arson

  • the willful or malicious damage or destruction of property by means of fire or explosion.
• Class A

  • cloth, wood, paper, plastics, rubber, and thrash
  • how to extinguish: for this type of fire, simply using water can put out the fire
• Class B

  • Liquid Fuels - alcohols, gasoline, lacquers, oil-based paint, petroleum oil and grease, solvents
  • Gas Fuel - propane and butane
  • How to Extinguish: This type of fire can be extinguished by forming a blockade between oxygen and the fuel, for instance, by applying a layer of foam
• Class C

  • Class A & B + Powered Electrical Equipment like home appliances, motors, and transformers
  • How to Extinguish: Carbon Dioxide or Dry Chemical Agents are usually used. Because of the involvement of electricity, extinguishing this fire type by water is very dangerous and out of the question.
• Class D

  • Metals - Aluminum, Lithium, Magnesium, Potassium, Sodium, Titanium, and Zirconium, most of which are usually contained in automobiles
  • How to Extinguish: Salt-based special powders and clean dry sand
• Class K

  • Cooking oils and greases (Animal-and-Vegetable-fat derived)
  • How to Extinguish: Only a fully-protected firefighter should deal with such fires
• Types of Fire Extinguisher