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Fire is No Accident It can be prevented. 2
3 States of Matter Solid Liquid Gas 3
What is Fire? Answer: Fire is a phenomena that occurs when a substance combines with fuel and has adequate oxygen. Typically it gives off heat, smoke and bright light. But it is not all that simple! 4
How Do Fires Start? For a fire to start: A combustible substance must be present. The temperature must be high enough to cause combustion. Enough oxygen must be present to sustain rapid combustion. It gets more complicated! 5
Chemistry of Fire Oxygen combines with other substances to produce new products this is called oxidation. When the process happens slowly, it can be called rusting. When the process happens it can be called combustion. 6
Chemistry of Fire Stored chemical energy is converted to energy in the form of heat and light. The energy comes from the breaking and formation of chemical bonds. 7
Chemistry of Fire Once a fire starts it will continue to burn until: the supply of oxygen is exhausted the fuel is removed the fuel is consumed someone extinguishes it 8
How Hot is Hot? The heat of combustion is an exothermic reaction it gives off heat. 9
Activation Energy Activation energy is the minimum energy necessary for a specific chemical reaction to occur (i.e., matches, electrical discharges, sparks, and chemicals). 10
Definitions of Terms for Solid Fuels Ignition temperature the temperature to which a fuel must be heated to initiate combustion sometimes called the autoignition temperature Every fuel has an ignition temperature! 11
Heat and Fuel Fuel needs to be in a gaseous state to ignite. The temperature must be high enough to vaporize the fuel. 12
Spontaneous Combustion Spontaneous combustion is a type of combustion which occurs without an external ignition source. Heat builds up to the point of ignition. Uses chemicals to supply oxygen such as oxidizing agents. 13
Combustion Requirements A fuel must be present. Oxygen must be available in sufficient quantity. Heat must be applied to initiate combustion. Sufficient heat must be generated to sustain the reaction. 14
Definition of Terms for Flammable Liquids and Gases Flash Point The minimum temperature at which a liquid fuel will produce enough vapor to burn is its flash point. Flammable Range The (range of) composition of fuel-air mixture required for combustion is the flammable range. 15
What is the Difference Between a Fire and an Explosion? Detonation The speed at which explosives decompose (detonation) varies greatly and permits the classification of explosives as high and low explosives. High order explosives have velocities of detonation more than 1,000 m/s (more than the speed of sound). Deflagration Low order explosives have velocities of detonation less than 1,000 m/s (less than the speed of sound). 16
Production of Smoke Carbon monoxide Carbon particles Carcinogens 17
Fire is No Accident It is the presence of two behaviors: acts by individuals to allow the right combination of components to be present omissions by individuals that allows the right combination of components to be present All fires have causes. It can be prevented. 18
The Fire Triangle This combination is sometimes called the fire triangle because it has three sides. 19
What Three Components are Required to Have a Fire Start? 20
Fuel Can be Solid, Liquid, id or Gas The more finely divided the fuel is the more likely it can be easily ignited. 21
Specific Solid Fuel Conditions Based on specific area and fire division, all combustible solids can be classified into three categories: Tinder Kindling Bulk fuel 22
Tinder: Specific Solid Fuel Conditions Surface Area Volume Density solids with a large amount of surface area and limited density can be ignited by very small heat sources 23
Kindling: Specific Solid Fuel Conditions Surface Area Volume Density solids with fairly high surface area and moderate density that can be ignited fairly easily requires a burning tinder for ignition. 24
Bulk Fuel: Specific Solid Fuel Conditions Surface Area Volume Density solids with specific surfaces that are dense requires burning kindling for ignition. 25
Specific Solid Fuel Conditions Surface Area Volume Density 26
Liquid or Gaseous Fuels Liquid fuels have physical properties p that: increase the difficulty of extinguishment are a hazard to personnel Gases tend to assume the shape of their container but have no specific volume. Specific Gravity is important. 27
Heat is the Enemy Now let s go back and review the concept of how heat plays a part in starting fires. 28
Sources of Heat 3 General Categories: Chemical Heat Energy Electrical Heat Energy Mechanical Heat Energy 29
Sources of Heat Electrical Heat Energy Resistance Heating Dielectric Heating Induction Heating Heat from Arcing Leakage Current Heating Static Electricity Lightning 30
Sources of Heat Mechanical Heat Energy Frictional Heat Friction Sparks Heat of Compression 31
Sources of Heat Chemical Heat Energy Two chemicals that combine to generate heat. 32
Sources of Heat Open Flame Arching 33
Sources of Heat Open Flame Heat is a form of energy that is measured in degrees of temperature to signify its intensity. Flame is the visible, luminous body of a burning gas. 34
Sources of Heat Arching Luminous discharge of current. 35
The Dynamics of Fire Oxygen (oxidizing agent) Fuel Heat Self sustained chemical reaction (also referred to as the chain reaction) 36
Fire Prevention Fire prevention consists of keeping these three things separated. This is where best management applies. 37
What are Some of the Causes? Cutting Grinding Welding Smoking Food preparation Vandalism Arson 38
Fire Suppression Consists of Separating Heat, Oxygen, and Fuel Cooling Temperature reduction Smothering Extinguishment by oxygen removal Starving Extinguishment by fuel removal 39
Flame Inhibition Dry Chemicals and Halons 40
How Does a Fire Spread? A rate of combustion or the spread of fire depends on several variables: the area of solid/liquid in contact with air the amount of heat generated to raise the temperature of un-burned portion the ability of materials to conduct heat away 41
How Does a Fire Spread? the area of solid/liquid in contact with air the amount of heat generated to raise the temperature of un-burned portion the ability of materials to conduct heat away 42
What Influences a Fire to Spread? Humidity Wind velocity Air Temperature 43
What are the Methods of Heat Transfer? Conduction Heat may be conducted from one body to another by direct contact of the bodies or by an intervening heat-conducting medium. 44
What are the Methods of Heat Transfer? Radiation Although air is a poor conductor, it is obvious that heat can travel where matter does not exist. This method of heat transmission is known as radiation of heat waves. 45
What are the Methods of Heat Transfer? Convection Convection is the transfer of heat by the movement of air or liquid. 46
How can a Small Fire Become a Big One in Such a Short Time? Phases that a fire goes through: Incipient Phase Smoldering Phase Low challenge Open Flame High Challenge Open Flame 47
Point of Origin The point of origin is the location where a fire begins. 48
Area of Origin The area of origin is a fire site where the combination of heat and fuel has resulted in damage or destruction. 49
How are Fires Classified? Class A Fires Class A fires involve ordinary combustible materials, such as wood, cloth, paper, rubber and many plastics. The cooling or quenching effect reduces the temperature of the burning Class A material below its ignition temperature. 50
How are Fires Classified? Class B Fires Class B fires involve flammable liquids, greases, and gases. The smothering or blanketing effect of oxygen exclusion is most effective. Other extinguishing methods include removal of fuel and temperature reduction. 51
How are Fires Classified? Class C Fires Class C fires involve energized electrical equipment. 52
How are Fires Classified? Class D Fires Class D fires involve combustible metals, such as magnesium, titanium, zirconium, sodium and potassium The extremely high temperature of some burning metals makes water and other common extinguishing agents ineffective. 53
How are Fires Classified? Class K Fires Class K is a new classification of fire as of 1998. It involves fires in combustible cooking fuels such as vegetable or animal fats. Its fuels are similar to Class B fuels but involve high temperature cooking oils and therefore have special characteristics. 54
Extinguisher Use the right type of extinguisher for the right class of fire. Water Blanket Extinguisher 55
Products of Combustion Fire gases Flame Heat Smoke 56
The Importance of Time Delay of alarm is deadly. 57
Fire is Never An Accident Keeping heat away yfrom fuel or Keeping fuel away from heat is what fire prevention is all about Fires can be prevented. 58
The End Can an ounce of prevention be worth a pound of cure? 60