Fire Loss Control RULE 1940 – Fire Protection and Control Basic Chemistry of Fire TRIANGLE OF FIRE Basic Chemistry of Fire THE THREE ELEMENTS Fuel • Another term for combustible materials. • This includes many substances such as natural gas (methane), plastics, wood, natural and artificial fibers, paper, coal and other living matter. • Inorganic substances are also combustible, substances like hydrogen, ammonium nitrate magnesium, phosphorus, sodium and sulfur. Fuel Basic Chemistry of Fire THE THREE ELEMENTS Oxidizing Agent (Oxygen) Oxygen • Fire normally draws its fire through the air, which is a mixture of 21 percent oxygen and 78 percent nitrogen. • 16% of oxygen is needed to sustain fire. • Other oxidizing agent in absence of oxygen – nitrates, peroxides, iodine, chlorine. Fuel Basic Chemistry of Fire Heat THE THREE ELEMENTS Heat Oxygen • Sufficient heat to raise the temperature of the fuel surface to a point where chemical union of the fuel and oxygen occurs. • The temperature at which the substance gives off these vapors or gases in sufficient quantity to be ignited is called the “flash point” of the substance. • Flash point – liquid. • Fire point or ignition temperature – solid. Fuel Basic Chemistry of Fire Heat Chemical Reaction THE FOURTH ELEMENT Chemical Reaction Oxygen • Fire is a chemical chain reaction of oxidation-reduction, a process of combustion in which there is a rapid oxidation of fuel at an elevated temperature (flashpoint). • One substance gains oxygen (oxidation) and another substance lose oxygen (reduction). • The reaction process releases energy and produces heat & light and gaseous by-products (carbon dioxide and water vapor). Fuel Basic Chemistry of Fire TETRAHEDRON OF FIRE Basic Chemistry of Fire FIRE • The result of the chemical combination of a combustible material (fuel) with oxygen in the presence of enough heat. • If any one of the four is missing, a fire will not start. The relationship is called tetrahedron of fire. • It is important that every worker, not only supervisor, knows the main causes of fire, how fire spreads, how to fight fire, and how to prevent fire. Heat Transfer • The chemical reaction produces energy more than needed and part of this is released as heat. • Heat transfer is from high temperature to an area of lower temperature. • The three methods of transfer are through conduction, convection and radiation. Heat Transfer THE THREE METHODS OF TRANSFER 1. Conduction • Transfer of heat between solid substances that are in direct contact with each other and has different temperature. Heat Transfer THE THREE METHODS OF TRANSFER 2. Convection • This takes place in liquid or gases. Liquid and gases when heated, expand and becomes less dense. This causes them to rise and denser and cooler liquid or gases are displaced (convection current). • This is repeated until all liquid or gases affected by the convection current have uniform temperature. Heat Transfer THE THREE METHODS OF TRANSFER 3. Radiation • Transfer of heat through electromagnetic waves in the infra-red part of spectrum. • It is the process of heat transmission between substances that are not in direct contact with each other. Heat Transfer THE THREE METHODS OF TRANSFER Phases of Burning THE FOUR PHASES ARE: 1. Incipient or ignition phase 2. Free-burning or growth phase 3. Fully-developed phase 4. Smoldering or decay phase Phases of Burning 1. INCIPIENT or IGNITION PHASE • Beginning or just started • Normal Oxygen 21% • Breathing is barely affected • Low temperatures Phases of Burning 2. FREE-BURNING OR GROWTH PHASE • Fire is expanding • Oxygen supply less than 21% • Breathing is difficult • Heat accumulates at the ceiling. Phases of Burning 2. FREE-BURNING OR GROWTH PHASE Phases of Burning 3. FULLY-DEVELOPED PHASE • All fuels are burning. • Maximum amount of heat is produced. Phases of Burning The rapid transition from free-burning to fullydeveloped is called FLASHOVER This happens when all materials in the room ignite all at once. Phases of Burning FLASHOVER Phases of Burning 3. FULLY-DEVELOPED PHASE Phases of Burning 4. SMOLDERING OR DECAY PHASE • Free-burning has ended. • Insufficient oxygen, less than 16%. • Normal breathing not possible. • Backdraft may happen. Phases of Burning A sudden explosion due to introduced oxygen is called BACKDRAFT Phases of Burning BACKDRAFT Phases of Burning BACKDRAFT Extinguishment of Fire Heat Chemical Reaction REMOVAL OF THE 4 ELEMENTS Starvation Oxygen • Removal of fuel. • Examples - Shut off valve, de-energize electrical equipment. Fuel Extinguishment of Fire Heat Chemical Reaction REMOVAL OF THE 4 ELEMENTS Smoldering • Removal of oxygen. • Examples – CO2 is used to sweep away oxygen. Oxygen Fuel Extinguishment of Fire Heat Chemical Reaction REMOVAL OF THE 4 ELEMENTS Cooling • Removal of heat. • Examples – Immerse with water. Oxygen Fuel Extinguishment of Fire Heat Chemical Reaction REMOVAL OF THE 4 ELEMENTS Interference Oxygen • Applying extinguishing agents that inhibit chemical reaction in a molecular level. • Examples – Using BCF or Halon Extinguishers, fire grenades. Fuel Classification of Fires Class A: ordinary combustibles Class B: flammable liquids Class C: energized electrical Class D: combustible metals Class K: cooking materials Classification of Fires CLASS A • Ordinary combustible materials like wood, paper, cloth, plastic and natural fibers • Water is effective to reduce temperature. Classification of Fires CLASS B • Flammable liquids greases and gases like gasoline kerosene, oil, methane and butane • Foam, vaporizing liquids, carbon dioxide and dry powder are commonly used to extinguish these fires. Classification of Fires CLASS C • Energized electrical equipment like wires, motors, switches, lights, cables, receptacle and computers. • De-energize first before using non-conductive extinguishing agents. Classification of Fires CLASS D • These involve combustible metals like magnesium, titanium, zirconium, sodium and potassium. Identifies by the suffix “IUM”. • They react violently with water. This has extremely high temperature that is why water and common extinguishing agents usually ineffective. Classification of Fires CLASS K • Kitchen fires from cooking oils or fats. • CLASS F under European systems. • Subclass of CLASS B (flammable liquids). Classification of Fires CLASS K Fire Extinguishers COMMON PORTABLE FIRE EXTINGUISHERS 1. Dry Chemical • • • Multi-Purpose Red Used for ABC 2. Halogenated or Clean Agent • • • • Ozone depleting halocarbon agents (HCFC) Green Used for ABC Most commonly used in electrical equipment. Fire Extinguishers COMMON PORTABLE FIRE EXTINGUISHERS 3. Foam • • • • AFFF Usually blue Used for AB Intended to cool fire and coat fuel. Fire Extinguishers PART OF FIRE EXTINGUISHER • Carrying handle • Operating lever • Locking pin • Pressure gauge • Discharge nozzle or horn • Label • Inspection tag Fire Extinguishers FIRE EXTINGUISHER USAGE • Before using keep your back in an unobstructed emergency exit. • Stand at least 6-8 feet from the fire • Remember the PASS-word THANK YOU!
