0. Essentials of Fire Fighting, 5th Edition
Chapter 14 — Fire Streams
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1. Chapter 14 Lesson Goal
After completing this lesson, the student shall be able to effectively apply fire fighting foam using various foam types, concentrates, and delivery devices following the policies and procedures set forth by the authority having jurisdiction (AHJ).
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2. Specific Objectives
1. Describe the suppression characteristics of fire fighting foam.
2. Define terms associated with types of foam and the foam-making process.
3. Discuss how foam is generated.
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3. Specific Objectives 4. Discuss foam concentrates.
5. Describe methods by which foam may be proportioned.
6. Discuss foam proportioners.
7. Discuss foam delivery devices.
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4. Specific Objectives
8. List reasons for failure to generate foam or for generating poor-quality foam.
9. Describe foam application techniques.
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5. Specific Objectives
10. Discuss hazards associated with foam concentrates.
11. Place a foam line in service — In-line eductor. (Skill Sheet 14-II-1)
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6. Ways Fire Fighting Foam Extinguishes/Prevents Fire
Separating
Cooling
Smothering
Penetrating
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7. Terms Associated With Foam
Foam concentrate
Foam proportioner
Foam solution
Foam (finished foam)
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8. How Foam is Generated
Foams used today are of mechanical type and before use must be
Proportioned
Aerated
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9. How Foam is Generated Elements needed to produce fire fighting foam
Foam concentrate
Water
Air
Mechanical agitation
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10. How Foam is Generated
All elements must be present and blended in correct ratios
Aeration produces foam bubbles to form effective foam blanket
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11. Foam Expansion The increase in volume of foam when aerated
Method of aerating results in varying degrees of expansion
Types of foam
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12. Foam Concentrates — General Considerations
Foam concentrates must match fuel to which applied
Class A foams not designed to extinguish Class B fires
Class B foams designed solely for hydrocarbon fires will not extinguish polar solvent fires
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13. Class A Foam
Increasingly used in both wildland and structural fire fighting
Special formulation of hydrocarbon surfactants
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14. Class A Foam
Aerated Class A foam coats, insulates fuels, preventing pyrolysis and ignition
May be used with variety of nozzles
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15. Class B Foam
Used to prevent ignition of or extinguish fires involving flammable and combustible liquids
Used to suppress vapors from unignited spills of these liquids
Several types of Class B foam concentrates available
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16. Class B Foam Manufactured from synthetic or protein base
May be proportioned into the fire stream through fixed system, apparatus-mounted system, or by portable foam proportioning equipment
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17. Class B Foam
Foams such as AFFF and FFFP foam may be applied with standard fog nozzles or air-aspirating foam nozzles
Rate of application depends on several factors
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18. Class B Foam
Unignited spills do not require same application rates as ignited spills
To be most effective, blanket of foam 4 inches (100 mm) thick should be applied to fuel surface
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19. Specific Application Foams
Numerous types of foam available for specific applications
Properties of foams vary
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20. Proportioning
Mixing of water with foam concentrate to form foam solution
Most concentrates can be mixed with fresh/salt water
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21. Proportioning
For maximum effectiveness, foam concentrates must be proportioned at designated percentage
Most fire fighting foams intended to be mixed with 94 to 99.9 percent water
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22. Proportioning Methods
Induction
Injection
Batch-mixing
Premixing
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23. Foam Proportioners — General Considerations
May be portable or apparatus-mounted
Operate by one of two basic principles
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24. Portable Foam Proportioners
Simplest, most common form of proportioning devices
In-line foam eductors
Foam nozzle eductors
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25. Apparatus-Mounted Proportioners
Mounted on structural, industrial, wildland, and aircraft rescue and fire fighting apparatus, as well as on fire boats
Three types
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26. Compressed-Air Foam Systems (CAFS)
Newer structural engines are equipped with CAFS
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27. Compressed-Air Foam Systems (CAFS)
Standard centrifugal pump supplies water, direct-injection foam-proportioning system mixes foam solution with water on discharge side of pump, onboard air compressor adds air to mix before discharging from engine
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28. Compressed-Air Foam Systems (CAFS)
Unlike other systems, hoseline contains finished foam
Advantages
Disadvantages
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29. Handline Nozzles Solid-bore nozzles Fog nozzles
Air-aspirating foam nozzles
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30. Medium- and High-Expansion Foam Generating Devices
Produce foam that is semistable with high air content
Medium-expansion foam
High-expansion foam
Water-aspirating type nozzle
Mechanical blower generator
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31. Reasons for Poor-Quality Foam/ Failure to Generate Foam
Eductor, nozzle flow ratings do not match so foam concentrate cannot induct into fire stream
Air leaks at fittings cause loss of suction
Improper cleaning of proportioning equipment causes clogged foam passages
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32. Reasons for Poor-Quality Foam/ Failure to Generate Foam
Nozzle not fully open, restricting water flow
Hose lay on discharge side of eductor is too long
Hose is kinked and stops flow
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33. Reasons for Poor-Quality Foam/ Failure to Generate Foam
Nozzle is too far above eductor
Mixing different types of foam concentrate in same tank results in mixture too viscous to pass through eductor
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34. Roll-On Foam Application Method
Directs foam stream on ground near front edge of burning liquid spill
Foam rolls across surface of fuel
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35. Roll-On Foam Application Method
Firefighters continue to apply foam until spreads across entire surface of fuel and fire extinguished
Used only on pool of liquid fuel on open ground
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36. Bank-Down Foam Application Method
May be employed when elevated object is near/ within area of burning pool of liquid or unignited liquid spill
Object may be wall, tank shell, similar vertical structure
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37. Bank-Down Foam Application Method
Foam stream directed onto object, allowing foam to run down onto surface of fuel
Used primarily in dike fires, fires involving spills around damaged/ overturned transport vehicles
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38. Rain-Down Foam Application Method
Used when other two methods not feasible because of size of spill area or lack of object from which to bank foam
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39. Rain-Down Foam Application Method
Primary manual application technique on aboveground storage tank fires
Directs stream into air above fire/spill, allows foam to float gently down onto surface of fuel
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40. Foam Hazards to Humans
Foam concentrates pose minimal health risks to humans
May be mildly irritating to skin, eyes
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41. Foam Hazards to Humans Affected areas should be flushed with water
Some concentrates, vapors may be harmful if ingested/inhaled
Consult MSDS for specific information
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42. Foam Hazards to Equipment
Most Class A, Class B foam concentrates are mildly corrosive
Follow proper flushing procedures to prevent damage
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43. Foam Hazards to Environment
Primary impact is effect of finished foam after application to fire/liquid spill
Biodegradability of foam determined by rate at which environmental bacteria cause decomposition
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44. Foam Hazards to Environment
Environmental impact of foam concentrates varies
In the U.S., Class A foams should be approved by USDA Forest Service
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45. Foam Hazards to Environment
Chemical properties of Class B foams and environmental impact vary on type and manufacturer
Protein-based foams safer for environment
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46. Summary
Firefighters must know the differences between the classes of foam, how to generate foam, and how to apply foam most effectively
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47. Review Questions
1. What are the ways that fire fighting foam extinguishes and/or prevents fire?
2. Describe types of foam concentrates.
3. What are the methods by which foam may be proportioned?
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48. Review Questions
4. What are the types of portable foam proportioners and how do they work?
5. Describe the techniques used to apply foam.
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