ARSON

• Fire


  The manifestation of rapid chemical reaction occurring between fuel and an oxidizer- typically the oxygen in the air. Such rapid chemical reaction releases energy in the form of heat and light.
• Fire


  Heat and light resulting from the rapid combination of oxygen, or in some cases gaseous chlorine, with other materials. The light is in the form of a flame, which is composed of glowing particles of the burning material and certain gaseous products that are luminous at the temperature of the burning material.
• Fire triangle


  • Three things required for combustion or fire: Fuel (Combustible materials to vaporize and burn), Oxygen (Oxygen in air is the common oxidizing agent, to combine with fuel vapor, air contains 28% O, 78% N, 1% inert gas), Heat (to raise the temperature of the fuel vapor to its ignition temperature)
• Fire tetrahedron


  • Illustrates how flaming combustion is supported and sustained through the chain reaction
  • Each face touches the other three faces
• Pyrolysis


  The chemical decomposition of matter through the action of heat, causing a change from a solid state to vapor state
• Flaming mode of combustion


  Gas-phased combustion
• Surface mode (Glowing) of combustion


  Condensed phased combustion
• Explosion


  Combustion process confined with pressure
• Detonation


  Combustion propagating at supersonic speed
• Free radicals


  Combustible vapors such as hydrogen gas, carbon monoxide, carbon dioxide, and nitrogen
• Types of flames based on color and completeness of combustibility of fuel


  • Luminous flame
  • Non-luminous flame
• Fuels (Combustible materials)


  Matter that exists in three physical states: solid, liquid and gas. Solids melt to become liquids, and these may vaporize and become gases. At high enough temperature all fuels can be converted to gases.
• Pyrolyzable solid fuels


  Fuels like wood, paper where vapors released by chemical decomposition support flaming combustion
• Non-pyrolyzable solid fuels


  Solid fuels like charcoal that are difficult to ignite because there are no pyrolyzable elements present, resulting in glowing combustion
• Types of solid fuels

  • Biomass (replaceable organic matters like wood, garbage, animal manure)
  • Fabrics and textiles (natural fibers like cotton, wool, silk; synthetic/artificial fibers like cellulose, fiber glass, steel)
• Classification of fibers

  • Natural fibers (plant, animal, mineral)
  • Synthetic/artificial fibers (organic, cellulose, non-cellulose, inorganic)
• Fiber


  Very fine thin strand or thread like object
• Fabric


  Twisted or woven fibers
• Textile


  Machine woven or knitted fabric
• Natural Fibers


  • Come from plants, animals, minerals
• Synthetic/Artificial Fibers


  • Organic fibers, cellulose fibers, cellulose acetate, noncellulose, and inorganic fibers like fiber glass, steel
• Limiting Oxygen Index (LOI)


  Numerical basis of measuring the tendency of a fabric to continuously burn once source of ignition is removed
• Plastics


  Included as ordinary fuels under class A except those materials of or containing cellulose nitrate
• Cellulose Nitrate


  Chemical powder used in bombs, also called pyroxylin
• Plastics


  Solid in the finished state although at some stage of manufacture plastics can be made to flow into a desired shape, usually through the application of heat or pressure or both
• Forms of coal

  • Lignite or brown coal
  • Sub-bituminous coal
  • Bituminous coal
  • Anthracite
• Bituminous coal


  • Most plentiful and important coal used by industry, contains more carbon and produces more heat than either lignite or sub-bituminous coal, best suited for making coke
• Anthracite


  • Least plentiful and hardest coal, contains more carbon and produces more heat than other coals, but difficult to ignite and burns slowly
• Peat


  Partially decayed plant matter found in swamps called bags and used as a fuel chiefly in areas where coal and oil are scarce
• General Groups of Liquid Fuels

  • Flammable liquids
  • Combustible Liquids
• Flammable liquids


  Liquids having a flash point of 37.8 C (100 F) and a vapor pressure not exceeding 40 psia (2068.6 um) at 37.8 C
• Combustible Liquids


  Liquids having flash point at or above 37.8 C (100 F)
• Factors affecting the Rate of Flame Propagation and Burning of Liquids

  • Wind velocity
  • Temperature
  • Heat of combustion
  • Latent heat of evaporation
  • Atmospheric pressure
• Latent heat


  The quantity of heat absorbed by a substance from a solid to a liquid and from a liquid to gas. Conversely, heat is released during conversion of a gas to liquid or liquid to a solid.
• Characteristics of Gas Fuels


  • They are matters that have no definite shape
  • They are composed of very tiny particles (molecules) at constant random motion in a straight line
  • Gas molecules collide against one another and against the wall of the container and are relatively far from one another
• Classification of Gases


  • Based on Source
  • According to Physical Properties
  • According to Usage
• Natural Gas


  • Consists chiefly of methane, a colorless and odorless gas, usually mixed with compounds of foul-smelling elements like sulfur so gas leaks can be detected
• Liquefied Petroleum Gas (LPG) or Liquefied Natural Gas (LNG)


  • Butane and propane which make up a small proportion of natural gas, become liquids when placed under large amount of pressure and change back to gas when pressure is released
• Compressed Gas


  • Gas in which at all normal temperature inside its container; exist solely in the gaseous state under pressure
• Liquefied Gas


  • Gas, which, at normal temperature inside its container, exist partly in the liquid state and partly in gaseous state and under pressure as long as any liquid remains in the container