Extinguishing Agents   Chapter 4
Objectives <ul><li>Review and examine the basic components of the fire extinguishment process </li></ul><ul><li>Review the...
Objectives (cont’d.) <ul><li>Examine in detail the variety of agents used for fire extinguishment and explain the applicat...
Introduction <ul><li>Fire combustion process modeled by using a fire tetrahedron </li></ul><ul><li>Fire professionals use ...
Fire Extinguishment Theory <ul><li>Heat and temperature are not the same </li></ul><ul><li>Heat: form of energy </li></ul>...
Interruption of the Combustion Process <ul><li>Combustion is interrupted by removing one or more components of the fire te...
Temperature Reduction/Heat Removal <ul><li>Water cools temperature of fuel to below ignition temperature </li></ul><ul><li...
Fuel Removal <ul><li>Stop flow of liquid or gaseous fuel  </li></ul><ul><li>Wildland fires </li></ul><ul><ul><li>Remove ve...
Oxygen Depletion <ul><li>Reduce the amount of oxygen available to the combustion </li></ul><ul><ul><li>Cover pan containin...
Chemical Flame Inhibition <ul><li>Extinguishing agents interrupt the combustion reaction </li></ul><ul><li>Exact mechanism...
Extinguishment and Classification of Fires <ul><li>Classification of fire based on the type of fuel being burned </li></ul...
The Process and Agents of Extinguishment <ul><li>Water has ability to absorb heat energy more than all other elements exce...
Agents to Improve Plain Water <ul><li>Water not always best extinguisher for fires </li></ul><ul><ul><li>Gasoline fires or...
Additives to Improve Water Applications <ul><li>Several chemicals developed to increase water’s effectiveness when combine...
Wet Water <ul><li>Water with a wetting agent added </li></ul><ul><li>Wetting agent reduces surface tension of water  </li>...
Slippery Water <ul><li>Uses polymers, a plastic like additive </li></ul><ul><li>Increases amount of water moved through ho...
Thick Water <ul><li>Designed to improve water’s ability to provide insulating barrier surface of a solid fuel </li></ul><u...
Viscous Water <ul><li>Thickening agents added to water: </li></ul><ul><ul><li>Clings and adheres to surfaces of fuel by pr...
Water Application Methods <ul><li>Straight stream </li></ul><ul><li>Fog or spray </li></ul><ul><li>Water mist systems </li...
Straight Stream Water Applications <ul><li>Should not impact the thermal layer zones  </li></ul><ul><li>Cools temperature ...
Fog or Spray Water Applications <ul><li>Divides water stream into very small drops resulting in more water surface area </...
Water Mist Systems <ul><li>New research and technological improvements in nozzles and pressure systems demonstrate possibi...
Foams <ul><li>Long history of success </li></ul><ul><li>Two-powder foam to single-powder foam to mechanical foam </li></ul...
Foam Classifications <ul><li>Class A </li></ul><ul><ul><li>Extinguish Class A fires, or fires in combustible solids </li><...
AFFF Concentrate <ul><li>Combination of water and perfluorocarboxylic acid </li></ul><ul><li>Loses water content rather ra...
Application of Class A Foams <ul><li>Mixture of water, foam concentrate, and air </li></ul><ul><li>Can be made wetter or d...
Figure 4-4  Foam   expansion ratio and drain time
Wet Foam <ul><li>Smaller bubbles </li></ul><ul><li>Less expansion  </li></ul><ul><li>Fast drain times </li></ul><ul><ul><l...
Dry Foam <ul><li>High expansion ratio  </li></ul><ul><li>Fluffy and consists mainly of air </li></ul><ul><li>Slow drain ti...
Fluid Foam <ul><li>Medium to smaller bubbles </li></ul><ul><li>Moderate drain times </li></ul><ul><li>Works well for: </li...
Fire Extinguishing Chemicals and Other Agents <ul><li>Water is not always the best extinguishing agent </li></ul><ul><li>A...
Dry Chemicals <ul><li>Principle chemicals used for dry chemical agents: </li></ul><ul><ul><li>Sodium bicarbonate, potassiu...
Dry Chemicals (cont’d.) Figure 4-6  Stored pressure dry chemical extinguisher
Application of Dry Chemicals <ul><li>Two common arrangements: </li></ul><ul><ul><li>Stored pressure </li></ul></ul><ul><ul...
Carbon Dioxide <ul><li>Consist of high-pressure cylinders or low-pressure tanks containing carbon dioxide under pressure <...
Application of Carbon Dioxide <ul><li>Known as “dry ice” </li></ul><ul><li>Extinguishes fires by smothering </li></ul><ul>...
Halogenated Agents <ul><li>Halon 1301 emerged as effective extinguishing agent not serious toxic threat to humans </li></u...
Alternative (Clean) Halogenated Fire Extinguishing Systems <ul><li>Not effective against fires in certain chemicals or mix...
Clean Agent Application Methods <ul><li>Triggering detectors or manual release starts an alarm sequence </li></ul><ul><li>...
Special Extinguishment Situations <ul><li>Many metals and some chemicals are incompatible with water, dry powder, and carb...
Combustible Metal Fires Table 4-2  Extinguishing materials for some metal fires
Chemical Fires <ul><li>Encountered in high school or college labs, leather tanning plants, and wool dying processes </li><...
Pressurized Gas Fires <ul><li>Difficult to extinguish because the gas is under pressure </li></ul><ul><li>Damaged tank, fi...
Pressurized Gas Fires (Cont’d.) Figure 4-10  Diagrams of BLEVE events
Summary <ul><li>Fires extinguished by: </li></ul><ul><ul><li>Cooling, depleting the oxygen, removing fuel, or breaking cha...
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Chapter 04-Extinguishing Agents

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• Review and examine the basic components of the fire extinguishment process
• Review the five basic classifications of fire and explain the various types of agents used to extinguish or control fires in these five classifications
• Examine in detail the variety of agents used for fire extinguishment and explain the application methods for each of these agents
• Identify and explain the benefits of using the latest technological advances in fire extinguishing agents such as compressed air foam and ultrafine water mist systems

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Chapter 04-Extinguishing Agents

  1. 1. Extinguishing Agents Chapter 4
  2. 2. Objectives <ul><li>Review and examine the basic components of the fire extinguishment process </li></ul><ul><li>Review the five basic classifications of fire and explain the various types of agents used to extinguish or control fires in these five classifications </li></ul>
  3. 3. Objectives (cont’d.) <ul><li>Examine in detail the variety of agents used for fire extinguishment and explain the application methods for each of these agents </li></ul><ul><li>Identify and explain the benefits of using the latest technological advances in fire extinguishing agents such as compressed air foam and ultrafine water mist systems </li></ul>
  4. 4. Introduction <ul><li>Fire combustion process modeled by using a fire tetrahedron </li></ul><ul><li>Fire professionals use this model daily to extinguish fires </li></ul><ul><li>Fire professionals’ task is to select the method that will stop the progress of the fire quickly and safely </li></ul>
  5. 5. Fire Extinguishment Theory <ul><li>Heat and temperature are not the same </li></ul><ul><li>Heat: form of energy </li></ul><ul><ul><li>Defined as the molecular motion of the material </li></ul></ul><ul><li>Temperature: measure of average molecular velocity or degree of intensity of the heat </li></ul>
  6. 6. Interruption of the Combustion Process <ul><li>Combustion is interrupted by removing one or more components of the fire tetrahedron </li></ul><ul><li>Four extinguishment processes: </li></ul><ul><ul><li>Temperature reduction </li></ul></ul><ul><ul><li>Fuel removal </li></ul></ul><ul><ul><li>Oxygen removal </li></ul></ul><ul><ul><li>Breaking release of additional fuel from material </li></ul></ul>
  7. 7. Temperature Reduction/Heat Removal <ul><li>Water cools temperature of fuel to below ignition temperature </li></ul><ul><li>Insufficient cooling can lead to rekindling </li></ul><ul><li>Flammable vapors may continue to be released </li></ul><ul><li>If fuel temperature is above flash point, a source of ignition with sufficient energy will cause reignition </li></ul>
  8. 8. Fuel Removal <ul><li>Stop flow of liquid or gaseous fuel </li></ul><ul><li>Wildland fires </li></ul><ul><ul><li>Remove vegetation in front of the fire </li></ul></ul><ul><ul><li>Backfire or burn fuel in front of main fire </li></ul></ul>
  9. 9. Oxygen Depletion <ul><li>Reduce the amount of oxygen available to the combustion </li></ul><ul><ul><li>Cover pan containing burning food </li></ul></ul><ul><ul><li>Flood area with inert gas </li></ul></ul><ul><ul><li>Blanketing fuel with foam </li></ul></ul>
  10. 10. Chemical Flame Inhibition <ul><li>Extinguishing agents interrupt the combustion reaction </li></ul><ul><li>Exact mechanisms have not been completely determined </li></ul>
  11. 11. Extinguishment and Classification of Fires <ul><li>Classification of fire based on the type of fuel being burned </li></ul><ul><li>Five fire classifications: A, B, C, D, and K </li></ul><ul><ul><li>Each has own specific requirements for fire extinguishment </li></ul></ul>
  12. 12. The Process and Agents of Extinguishment <ul><li>Water has ability to absorb heat energy more than all other elements except mercury </li></ul><ul><ul><li>Non-conforming characteristic in processes of expansion and contraction </li></ul></ul><ul><li>Latent heat of vaporization: quantity of heat absorbed by a substance when it changes from a liquid to vapor </li></ul>
  13. 13. Agents to Improve Plain Water <ul><li>Water not always best extinguisher for fires </li></ul><ul><ul><li>Gasoline fires or other hydrocarbon liquids with flash points below 100°F should not use water </li></ul></ul><ul><ul><li>Water not effective on most metallic dusts and shavings, or in pyrophoric metals </li></ul></ul>
  14. 14. Additives to Improve Water Applications <ul><li>Several chemicals developed to increase water’s effectiveness when combined </li></ul><ul><ul><li>Temperature can be lowered </li></ul></ul><ul><ul><li>Can be made thicker </li></ul></ul><ul><ul><li>Surface tension can be reduced to decrease the amount of friction loss </li></ul></ul>
  15. 15. Wet Water <ul><li>Water with a wetting agent added </li></ul><ul><li>Wetting agent reduces surface tension of water </li></ul><ul><ul><li>Allows it to flow and spread better </li></ul></ul><ul><li>Used when need to penetrate deeply to reach seat of a fire in tightly baled materials </li></ul><ul><ul><li>Cotton </li></ul></ul><ul><ul><li>Tightly packed cardboard boxes </li></ul></ul>
  16. 16. Slippery Water <ul><li>Uses polymers, a plastic like additive </li></ul><ul><li>Increases amount of water moved through hose line </li></ul><ul><li>Reduces friction loss </li></ul><ul><ul><li>Pressure lost by fluids while moving through pipes, hoses, lines, or other limited spaces </li></ul></ul><ul><li>Flowing larger quantities of water will increase the reaction backpressure </li></ul>
  17. 17. Thick Water <ul><li>Designed to improve water’s ability to provide insulating barrier surface of a solid fuel </li></ul><ul><ul><li>Expensive </li></ul></ul><ul><ul><li>Reports on use have not been very positive </li></ul></ul>
  18. 18. Viscous Water <ul><li>Thickening agents added to water: </li></ul><ul><ul><li>Clings and adheres to surfaces of fuel by providing a continuous coating thicker than untreated water over the fuel surface </li></ul></ul><ul><ul><li>Projects further when discharged from nozzle </li></ul></ul><ul><ul><li>Better resists wind and air currents </li></ul></ul>
  19. 19. Water Application Methods <ul><li>Straight stream </li></ul><ul><li>Fog or spray </li></ul><ul><li>Water mist systems </li></ul><ul><li>Foams </li></ul>
  20. 20. Straight Stream Water Applications <ul><li>Should not impact the thermal layer zones </li></ul><ul><li>Cools temperature of ceiling area over fire </li></ul><ul><li>Highly effective on a high flash point liquid fire </li></ul>
  21. 21. Fog or Spray Water Applications <ul><li>Divides water stream into very small drops resulting in more water surface area </li></ul><ul><li>Absorbs great deal of heat </li></ul><ul><li>Can produce thermal imbalance between hot and cool smoke layers </li></ul><ul><li>Purges an area of smoky and noxious gases </li></ul>
  22. 22. Water Mist Systems <ul><li>New research and technological improvements in nozzles and pressure systems demonstrate possibility of efficient fire suppression </li></ul><ul><li>Dependant on: </li></ul><ul><ul><li>Mist droplet size </li></ul></ul><ul><ul><li>Mist stability </li></ul></ul><ul><ul><li>Transportation behavior of mist </li></ul></ul><ul><ul><li>Unobstructed nozzles </li></ul></ul><ul><ul><li>Efficiency and rate of droplet vaporization </li></ul></ul>
  23. 23. Foams <ul><li>Long history of success </li></ul><ul><li>Two-powder foam to single-powder foam to mechanical foam </li></ul><ul><li>Now surfactant or detergent foam is also used </li></ul><ul><ul><li>Better penetrates a porous solid fuel source as it reduces surface tension of water </li></ul></ul><ul><ul><li>Known as wet water or wetting agent </li></ul></ul>
  24. 24. Foam Classifications <ul><li>Class A </li></ul><ul><ul><li>Extinguish Class A fires, or fires in combustible solids </li></ul></ul><ul><li>Class B </li></ul><ul><ul><li>Extinguish Class B fires </li></ul></ul><ul><li>Special foams </li></ul><ul><ul><li>Compressed air foam systems </li></ul></ul><ul><li>Low, medium, or high expansion foam </li></ul>
  25. 25. AFFF Concentrate <ul><li>Combination of water and perfluorocarboxylic acid </li></ul><ul><li>Loses water content rather rapidly </li></ul><ul><li>May provide less burn-back resistance compared to other protein-based foams </li></ul>
  26. 26. Application of Class A Foams <ul><li>Mixture of water, foam concentrate, and air </li></ul><ul><li>Can be made wetter or dryer </li></ul><ul><li>Size of bubbles determined by air pressure </li></ul><ul><li>Wet, dry, and fluid foams </li></ul>
  27. 27. Figure 4-4 Foam expansion ratio and drain time
  28. 28. Wet Foam <ul><li>Smaller bubbles </li></ul><ul><li>Less expansion </li></ul><ul><li>Fast drain times </li></ul><ul><ul><li>Drain time : amount of time for the water to drain away from the foam solution </li></ul></ul><ul><li>Good for initial fire suppression, overhaul, and penetration into deep-seated fires </li></ul>
  29. 29. Dry Foam <ul><li>High expansion ratio </li></ul><ul><li>Fluffy and consists mainly of air </li></ul><ul><li>Slow drain times </li></ul><ul><li>Hold shape for a long period of time </li></ul><ul><li>Good for exposure protection </li></ul>
  30. 30. Fluid Foam <ul><li>Medium to smaller bubbles </li></ul><ul><li>Moderate drain times </li></ul><ul><li>Works well for: </li></ul><ul><ul><li>Direct attack </li></ul></ul><ul><ul><li>Exposure protection </li></ul></ul><ul><ul><li>Mop-up operations </li></ul></ul>
  31. 31. Fire Extinguishing Chemicals and Other Agents <ul><li>Water is not always the best extinguishing agent </li></ul><ul><li>Agents that have been developed to fill in for water: </li></ul><ul><ul><li>Dry chemicals </li></ul></ul><ul><ul><li>Carbon dioxide </li></ul></ul><ul><ul><li>Halogenated agents </li></ul></ul>
  32. 32. Dry Chemicals <ul><li>Principle chemicals used for dry chemical agents: </li></ul><ul><ul><li>Sodium bicarbonate, potassium bicarbonate, potassium chloride, and urea-potassium bicarbonate </li></ul></ul><ul><li>Used on Class B, D and K fires </li></ul><ul><li>Discharged under high pressure by gas expellant </li></ul><ul><li>Forms blanket over top of the fire </li></ul><ul><li>Extinguishes fire by excluding oxygen </li></ul>
  33. 33. Dry Chemicals (cont’d.) Figure 4-6 Stored pressure dry chemical extinguisher
  34. 34. Application of Dry Chemicals <ul><li>Two common arrangements: </li></ul><ul><ul><li>Stored pressure </li></ul></ul><ul><ul><li>Separate pressure container </li></ul></ul><ul><li>Activation can be manual, automatic, or both </li></ul><ul><li>Location of discharge nozzles need to be located in the center above the cooking surface </li></ul>
  35. 35. Carbon Dioxide <ul><li>Consist of high-pressure cylinders or low-pressure tanks containing carbon dioxide under pressure </li></ul><ul><li>Colorless, odorless, electrically non-conducive gas that is non-corrosive to most metals </li></ul>
  36. 36. Application of Carbon Dioxide <ul><li>Known as “dry ice” </li></ul><ul><li>Extinguishes fires by smothering </li></ul><ul><li>Creates a refrigerating effect </li></ul><ul><li>Creates shrill noise </li></ul><ul><li>Creates static electricity </li></ul>
  37. 37. Halogenated Agents <ul><li>Halon 1301 emerged as effective extinguishing agent not serious toxic threat to humans </li></ul><ul><ul><li>Seriously depleted the ozone layer surrounding the earth </li></ul></ul><ul><li>Production of certain halons used for extinguishing purposes banned in certain countries (Halon 1211,a liquid, and Halon 1301, a gas) </li></ul><ul><li>New “environmentally clean” agents developed </li></ul>
  38. 38. Alternative (Clean) Halogenated Fire Extinguishing Systems <ul><li>Not effective against fires in certain chemicals or mixtures of chemicals </li></ul><ul><li>Designed primarily for areas where persons are prohibited </li></ul><ul><li>Monthly inspection of the enclosure is needed </li></ul>
  39. 39. Clean Agent Application Methods <ul><li>Triggering detectors or manual release starts an alarm sequence </li></ul><ul><li>Control head provides gas escape route into atmosphere through discharge control valve </li></ul><ul><li>Escape of gas creates imbalance of pressure </li></ul><ul><li>Nozzles designed to distribute extinguishing agent at controlled rate, smoothly and evenly in fan-shaped patterns </li></ul>
  40. 40. Special Extinguishment Situations <ul><li>Many metals and some chemicals are incompatible with water, dry powder, and carbon dioxide extinguishing agents when burning </li></ul><ul><ul><li>May react violently when incompatible agents used </li></ul></ul><ul><ul><li>Specialized extinguishing agents are required </li></ul></ul>
  41. 41. Combustible Metal Fires Table 4-2 Extinguishing materials for some metal fires
  42. 42. Chemical Fires <ul><li>Encountered in high school or college labs, leather tanning plants, and wool dying processes </li></ul><ul><li>Runoff of contaminated water may impact groundwater </li></ul><ul><li>Imperative that firefighters make provisions to have persons who can provide technical expertise and advice respond to the incident </li></ul>
  43. 43. Pressurized Gas Fires <ul><li>Difficult to extinguish because the gas is under pressure </li></ul><ul><li>Damaged tank, fitting, or valve will provide a continuous supply of fuel </li></ul><ul><li>Where there is no fire, immediate evacuation required </li></ul><ul><li>Need to ensure gas supply cut off </li></ul><ul><li>Tank must be cooled </li></ul>
  44. 44. Pressurized Gas Fires (Cont’d.) Figure 4-10 Diagrams of BLEVE events
  45. 45. Summary <ul><li>Fires extinguished by: </li></ul><ul><ul><li>Cooling, depleting the oxygen, removing fuel, or breaking chain of combustion </li></ul></ul><ul><li>Water is not the only extinguishing agent </li></ul><ul><ul><li>Can be made more effective by making it slippery, reducing its surface tension, and making it thicker </li></ul></ul><ul><li>Carbon dioxide, dry chemicals, and foam also used as extinguishers </li></ul>
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