ARFF IFSTA Chapter 6

1. Aircraft Rescue and Fire
Fighting,
5th
Edition
Chapter 6 — Extinguishing
Agents

2. ARFF
6–2
Chapter 6 Lesson Goal
• After completing this lesson, the student
shall be able to describe types of
extinguishing agents and systems used
in aircraft rescue and fire fighting
operations.

3. ARFF
6–3
Objectives
1. Explain the use of water as an
extinguishing agent in aircraft rescue
and fire fighting operations.
2. Explain the use of foam as an
extinguishing agent in aircraft rescue
and fire fighting operations.
3. Identify types of foam
concentrates. (Continued)

4. ARFF
6–4
Objectives
4. Describe foam proportioning
systems.
5. Discuss portable foam application
devices.
6. Explain foam application.
(Continued)

5. ARFF
6–5
Objectives
7. Describe dry chemicals and
their applications.
8. Describe clean agents and their
applications.

6. ARFF
6–6
Water Use in ARFF
• Water — most commonly used
extinguishing agent in the fire service
• Alone not generally suitable for large
aircraft fuel fires
– Foaming agents added
– May push burning fuel away
– May increase size of Class B fires
(Continued)

7. ARFF
6–7
Water Use in ARFF
• Uses in ARFF operations
– Cool aircraft fuselage
– Controlling spot fires/eliminating reignition
sources
– Provide heat shield
• Preferred agent for Class A interior fires

8. ARFF
6–8
Structural Apparatus and Water
• Guidelines when used for spilled fuel
fire
– 1 ½-inch (38 mm) or larger lines
– Fog pattern
– Avoid straight streams
(Continued)

9. ARFF
6–9
Structural Apparatus and Water
• Structural apparatus water supply
– Does not carry as much water
– Supply may last long enough for personnel
to effect rescue

10. ARFF
6–10
Hazards of Water
• Excellent conductor
of electricity
• Steam can obscure
vision, scald
individuals

11. ARFF
6–11
Water and Aircraft Interior
Fires
• Straight stream — may be best in well-
involved, unventilated interior fires
• Straight stream advantages
– Will not upset thermal layering
– Will generate less steam
– Will have better reach

12. ARFF
6–12
Foam Use in Fire Fighting
• Used to combat fires in hydrocarbon
fuels
– Lower specific gravity than hydrocarbon
fuels
– Floats on surface
(Continued)

13. ARFF
6–13
Foam Use in Fire Fighting
• Works by forming blanket
– Excludes oxygen
– Stops burning process
• Water in foam
– Slowly released
– Provides cooling effect

14. ARFF
6–14
Foam Extinguishing Methods
• Separating
• Smothering
• Cooling
• Suppressing
(Continued)

15. ARFF
6–15
Foam Extinguishing Methods

16. ARFF
6–16
Applying Foam
• Applying foam
– Cools the fuel
– Prevents flammable vapors from mixing
with air to form a flammable mixture
• Foam blanket
– Should be homogeneous mass
– Minimally disrupted by factors
(Continued)

17. ARFF
6–17
Applying Foam
• As foam is applied
– Breaks down
– Water content drains out or vaporizes
• Foam must be applied
– In sufficient volume
– At an adequate rate
– Reapplied as necessary

18. ARFF
6–18
Critical Area
• Density and rate of application are
crucial
• Critical area
– Around aircraft fuselage
– Feasible to extinguish or control a fire for
rescue
• NFPA®
403 contains information

19. ARFF
6–19
Foam Proportioning
• Foams — must be proportioned and
aerated
• Requires specific factors
– Foam concentrate, water, air, and
mechanical aeration
– Removing an element
–No foam
–Poor-quality foam (Continued)

20. ARFF
6–20
Foam Proportioning
• The foam tetrahedron

21. ARFF
6–21
Terms
• Foam concentrate
• Foam proportioner
• Foam solution
• Finished foam

22. ARFF
6–22
Using Foam Concentrates
• Aeration — produce an adequate
amount of bubbles to form an effective
blanket
– Better aerated, longer blanket will last
– Air-aspirating foam nozzle/attachment
(Continued)

23. ARFF
6–23
Using Foam Concentrates
• Must match fuel to which applied
• Class A foams not designed to
extinguish Class B fires
• Class B fuels
– Hydrocarbons
– Polar solvents
(Continued)

24. ARFF
6–24
Using Foam Concentrates
• Hydrocarbon fuels
– Petroleum-based
– Hydrophobic
• Standard fire fighting foam
– Effective agent and vapor suppressant
– Float on surface of hydrocarbon fuels
(Continued)

25. ARFF
6–25
Using Foam Concentrates
• Polar solvents
– Flammable
– Hydrophilic

26. ARFF
6–26
Class A Foam
• Effective in incidents involving deep-
seated Class A fuels
• May be used to attack interior aircraft
cabin fires/structural-related fires
• Essentially wetting agents

27. ARFF
6–27
Class B Foam
• Uses
– Extinguish fires involving flammable and
combustible liquids
– Suppress vapors from unignited spills
• Proportioned into the fire stream via
apparatus-mounted or portable foam
proportioning equipment
(Continued)

28. ARFF
6–28
Class B Foam
• Do not mix different manufacturers’
foam concentrates
– Military specifications AFFF is exception
– Causes no adverse effects for military
specification AFFF
(Continued)

29. ARFF
6–29
Class B Foam
• Chemical properties and environmental
impact vary
– Generally not good for environment
– Use minimum needed
– Contain and recover aircraft fuel and foam
runoff

30. ARFF
6–30
Class B Foam: Proportioning
• Mixed in proportions from 1% to 6%
• Some multipurpose foams used on both
hydrocarbon and polar solvent fuels

31. ARFF
6–31
Class B Foam: Foam
Expansion
• Increase in volume of a foam solution
when it is aerated
• Expansion depends on factors
– Type and quality of foam concentrate
– Accurate proportioning
– Methods of aspiration
(Continued)

32. ARFF
6–32
Class B Foam: Foam
Expansion
• Depending on its purpose foam is:
– Low-expansion
– Medium-expansion
– High-expansion

33. ARFF
6–33
Class B Foam: Rates of
Application
• Depend on several variables
– Type of foam concentrate used
– Whether or not the fuel is on fire
– Type of fuel
– Whether fuel is spilled or in a tank
(Continued)

34. ARFF
6–34
Class B Foam: Rates of
Application
• NFPA®
403 states application rates
• Unignited spills — do not require same
application rates as ignited spills

35. ARFF
6–35
Specific Foam Concentrates
• Foams are selected based on:
– Properties
– Performance
• Consult the UL listing

36. ARFF
6–36
Aqueous Film Forming Foam
(AFFF)
• Recommended extinguishing agent for
hydrocarbon fuel fires
• Characteristics make it good for ARFF
operations
• Applied to a hydrocarbon fire causes
specific actions
(Continued)

37. ARFF
6–37
Aqueous Film Forming Foam
(AFFF)
• Available in 1%, 3%, or 6%
• Mixed with water
• Resists breakdown by dry chemicals
(Continued)

38. ARFF
6–38
Aqueous Film Forming Foam
(AFFF)
• How fast fire is extinguished depends
on:
– Manner applied
– Application rate
– Density
• Applied with an aspirating foam or
nonaspirating nozzle
(Continued)

39. ARFF
6–39
Aqueous Film Forming Foam
(AFFF)
• Alcohol-resistant AFFF is available
• Store AFFF in a temperature controlled
environment

40. ARFF
6–40
Regular Protein Foam and
Fluoroprotein Foam
• Protein foam
– Used widely before the 1970s in ARFF
– No longer widely used in ARFF
• Fluoroprotein foam
– Not widely used in ARFF
– Used to protect fuel tanks and petroleum
processing facilities

41. ARFF
6–41
Film Forming Fluoroprotein
Foam
• Incorporates benefits of aqueous film
and fluoroprotein foam
• Available in alcohol-resistant
formulation
• Effective agent on flammable liquid fires
(Continued)

42. ARFF
6–42
Film Forming Fluoroprotein
Foam
• Available in 3% and 6% solutions
• Effectiveness depends on:
– Application rate
– Density
– Blanketing of the fuel
• Not as effective as AFFF in foam
stability

43. ARFF
6–43
High-expansion Foams
• Special-purpose foams; detergent base
• Low water content
• Three basic applications
– Concealed spaces
– Fixed extinguishing systems
– Class A fire applications
• Varying expansion ratios

44. ARFF
6–44
How Foam Concentrates are
Stored
• Pails
• Barrels
• Intermediate bulk
containers
• Apparatus tanks
Courtesy of Doddy Photography.

45. ARFF
6–45
General Principles of Foam
Proportioning
• Strict design specifications for
equipment
• Failure to operate equipment
– Poor-quality foam
– No foam
(Continued)

46. ARFF
6–46
General Principles of Foam
Proportioning
• Operate by one of two principles
– Venturi effect
– Injection into water stream
• Low-energy foam system — uses a fire
pump
• High-energy foam systems — introduce
compressed air

47. ARFF
6–47
Foam Proportioning
• Proportioning — mixing of water with
foam concentrate
• Failure to proportion correctly
– Poor-quality foam
– Waste resources
(Continued)

48. ARFF
6–48
Foam Proportioning
• ARFF apparatus foam system testing
– FAA recommends at least twice a year
– Refractometer or conductivity meter
• Concentrates are mixed with 94 to 99.9
percent water
(Continued)

49. ARFF
6–49
Foam Proportioning
• Selection of proportioner depends on
several factors
• Four basic methods
– Induction
– Injection
– Batch mixing
– Premixing

50. ARFF
6–50
Foam Proportioning: Induction
• Uses the pressure energy in stream of
water to induct foam concentrate into
the fire stream
• Stream of water passes through an
eductor
• Examples: In-line eductors and foam-
nozzle eductors

51. ARFF
6–51
Foam Proportioning: Injection
• Uses an external pump or water
pressure to force foam concentrate into
the fire stream
• Used in apparatus-mounted or fixed-fire
protection systems
• Examples: Direct injection and
balanced pressure proportioners

52. ARFF
6–52
Foam Proportioning: Batch
Mixing
• Pouring an appropriate amount of foam
concentrate into a tank of water
• Simplest method
• Used with regular AFFF and Class A
• Disadvantage — all water is converted
to foam solution

53. ARFF
6–53
Foam Proportioning: Premixing
• Premeasured portions of water and
foam concentrate are mixed
• Commonly used

54. ARFF
6–54
Portable Foam Proportioners
• Simplest and most
common foam
proportioning devices
• Three common types
– In-line foam eductors
– Foam nozzle eductors
– Self-educting master
stream nozzles (Continued)

55. ARFF
6–55
Portable Foam Proportioners
• In-line eductors — most common type
in structural fire service
• Foam nozzle eductor — eductor is built
into the nozzle
• Self-educting master stream foam
nozzle — used where flows in excess of
350 gpm (1 400 L/min) are required

56. ARFF
6–56
Apparatus-mounted Foam
Proportioning Systems
• Systems are commonly mounted on
vehicles
– Fire boats
– Structural, industrial, wildland, and ARFF
fire apparatus
• Majority can be used for both Class A
and Class B foam concentrates
(Continued)

57. ARFF
6–57
Apparatus-mounted Foam
Proportioning Systems
• Installed in-line eductors
– Permanently attached to apparatus
pumping system
– Same precautions as portable in-line
eductors
– Supplied from pickup tubes or foam
concentrate tanks
(Continued)

58. ARFF
6–58
Apparatus-mounted Foam
Proportioning Systems
• Around-the-pump
proportioners
– Rated for specific flow
– Have disadvantages
(Continued)

59. ARFF
6–59
Apparatus-mounted Foam
Proportioning Systems
• Balanced-pressure and direct-injection
proportioners
– Used by most ARFF apparatus
– Various types of systems
• Each system has advantages and
limitations
(Continued)

60. ARFF
6–60
Apparatus-mounted Foam
Proportioning Systems
• Systems include
– Bypass-type balanced pressure
proportioners
– Variable-flow demand-type balanced-
pressure proportioners
– Variable-flow variable-rate direct-injection
systems

61. ARFF
6–61
High-energy Foam Generating
Systems
• Introduce compressed air into foam
solution prior to discharge
• Uses a standard centrifugal fire pump to
supply water
(Continued)

62. ARFF
6–62
High-energy Foam Generating
Systems
• Called a compressed-air foam system
(CAFS)
• Most commonly found on structural and
wildland fire apparatus

63. ARFF
6–63
Portable Foam Application
Devices
• Foam solution must be mixed with air
• Low-energy foam systems — aeration
and discharge accomplished by a fog
nozzle or a foam nozzle
(Continued)

64. ARFF
6–64
Portable Foam Application
Devices
• Low-expansion foams — discharged
through handline nozzles or master
stream devices

65. ARFF
6–65
Portable Foam Application
Devices: Handline Nozzles
• “Any nozzle that one to three firefighters
can safely handle and that flows less
than 350 gpm (1 400 L/min)”
• Two most common
– Standard fog nozzles
– Air-aspirating foam nozzles
(Continued)

66. ARFF
6–66
Portable Foam Application
Devices: Handline Nozzles
• Low-expansion, short
lasting foam —
produced by fixed-flow
or automatic fog nozzles
• Air-aspirating foam
nozzle — uses a venturi
action
Courtesy of John Demyan, LVI
Airport.

67. ARFF
6–67
Portable Foam Application
Devices: Turret Nozzles
• Large, pre-plumbed master stream
appliances
• Capable of sweeping side to side and
delivering large volumes of foam or
water
(Continued)

68. ARFF
6–68
Portable Foam Application
Devices: Turret Nozzles
• May be aspirating, nonaspirating, or
combination
• Consider several factors when
selecting

69. ARFF
6–69
Aspirating Versus
Nonaspirating Nozzles
• Nonaspirating application — only film
forming foams
• Protein or fluoroprotein foams —
require air-aspirating nozzles
• AFFF — aspirating or nonaspirating
turrets and nozzles
(Continued)

70. ARFF
6–70
Aspirating Versus
Nonaspirating Nozzles
• Nonaspirating nozzles — advantages
and limitations
• Air-aspirating devices — designed to
produce a good quality foam

71. ARFF
6–71
Foam Application Techniques
• Correct application — as important as
type of agent
• Principle of “insulate and isolate”
– Insulate the fuselage
– Separate fire from the fuselage

72. ARFF
6–72
Foam Application Techniques:
Roll-on Method
• Directs the foam stream on the ground
near the front edge of a burning liquid
pool
• Foam rolls across fuel surface
(Continued)

73. ARFF
6–73
Foam Application Techniques:
Roll-on Method
• Continue to apply
foam across entire
fuel surface
• Used only on a
pool of liquid fuel
on the ground or
pavement
Courtesy of James Mack,
Richmond International Airport

74. ARFF
6–74
Foam Application Techniques:
Deflection or Bank-down
Method
• Used when an
elevated object is
near a burning pool
of liquid or unignited
spill
• Direct the foam
stream at the object
Courtesy of James Mack,
Richmond International Airport

75. ARFF
6–75
Foam Application Techniques:
Base-of-the-Fire Method
• AFFF can be applied
with a zero-degree
“base-of-the-fire”
angle
• Usually applied
through a bumper
turret
Courtesy of James Mack,
Richmond International Airport

76. ARFF
6–76
Foam Application Techniques:
Rainfall Method
• 40 degree rainfall method — extends
reach of foam stream
• Consider wind
• Used when other methods are not
feasible
(Continued)

77. ARFF
6–77
Foam Application Techniques:
Rainfall Method
• Primary technique used on
aboveground storage tank fires

78. ARFF
6–78
Dry Chemicals
• Dry-chemical agents — used on Class
A, B, or C fires
• Dry-powder agents — used only on
Class D fires
(Continued)

79. ARFF
6–79
Dry Chemicals
• Effective
– For initial attack and quick knockdown of
certain fires
– On three-dimensional or running fuel fires
• Not effective on large spill fires with
obstructions
(Continued)

80. ARFF
6–80
Dry Chemicals
• Do not have vapor-sealing properties
or flashback-preventive characteristics
of foam
• Inhibit chemical chain reaction
• Are nonconductive
• May contain a number of chemical
compounds
(Continued)

81. ARFF
6–81
Dry Chemicals
• Compatible
– With film-forming foams
– With water and foam for master stream or
turret operations
• Hydro-Chem — use of dry chemical,
water and AFFF
(Continued)

82. ARFF
6–82
Dry Chemicals
• Guidelines for applying
– Apply from upwind
– Apply so agent will blanket fire
– Be aggressive but do not splash or churn
fuel
– Monitor fire area for reignition
(Continued)

83. ARFF
6–83
Dry Chemicals
• Are nontoxic, generally considered
safe to use
– Cloud of chemicals may reduce visibility
– Respiratory irritant
– Wear SCBA

84. ARFF
6–84
Dry Chemicals: Extinguishers
• Consult the UL listing
for rating
• Two basic types
– Regular B:C rated
– Multipurpose A:B:C-
rated
• Additives are mixed
with base
Courtesy of Doddy Photography
(Continued)

85. ARFF
6–85
Dry Chemicals: Extinguishers
• Handheld and wheeled
extinguishers
– Stored-pressure
– Cartridge operated
• Wheeled units are similar
to handheld units but
larger

86. ARFF
6–86
Apparatus Mounted Units
• ARFF apparatus may
be equipped with dry-
chemical or wet-
chemical extinguishing
systems
• Consist of several
components
(Continued)

87. ARFF
6–87
Apparatus Mounted Units
• FAR Part 139.317 lists requirements
• ARFF vehicles carry dry chemical as
an auxiliary agent
– Usually Purple K
– Compatible with AFFF
• Systems start at 500 lb (227 kg)
(Continued)

88. ARFF
6–88
Apparatus Mounted Units
• Dry chemical is dispensed in three
ways
– Handline
– Piggybacking systems
– Water stream injection systems
• Handlines and turrets must meet
specific requirements

89. ARFF
6–89
Clean Agents
• Designed to extinguish fires and leave
little, if no, residue
• Traditional agents — Halon 1211 and
Halon 1301
– Halogens phased-out by 2000
– Exceptions for essential uses
(Continued)

90. ARFF
6–90
Clean Agents
• Clean agent systems are being
replaced
– Because of high cost
– Changing to dry chemical or PKP systems
• Halon replacements — often require
higher concentration
(Continued)

91. ARFF
6–91
Clean Agents
• Halotron®
I — approved by FAA and
EPA as a “clean agent” replacement
• Progress in replacing halogenated
agents

92. ARFF
6–92
Characteristics of Halons
• Rapidly vaporize in fire
• Nonconductive
• Almost no flashback-preventive
capabilities
(Continued)

93. ARFF
6–93
Characteristics of Halons
• Penetrate inaccessible areas
• Effective for fires in complex equipment
• Compatible with dry chemicals and
AFFF

94. ARFF
6–94
Summary
• ARFF personnel should be familiar with
the common extinguishing agents they
will use to fight aircraft fires.
• Water, foam, dry-chemical, dry-powder,
and clean agents all have specific uses
in ARFF fire fighting.
(Continued)

95. ARFF
6–95
Summary
• Foam applications are the most widely
used due to their greater ability to
extinguish hydrocarbon and polar
solvent fuel fires.
(Continued)

96. ARFF
6–96
Summary
• Personnel should be familiar with the
proportioning process through which
fuel concentrate becomes finished
foam.
• Personnel should understand the four
methods used to apply foam as well as
foam application equipment.
(Continued)

97. ARFF
6–97
Summary
• Firefighters must have a working
knowledge of dry-chemical, dry-powder,
and clean agent extinguishing agents.

98. ARFF
6–98
Review Questions
1. Why is water alone not usually
a suitable extinguishing agent for
large aircraft fuel fires?
2. What are the methods by which
foam extinguishes or prevents fire?
3. How is foam induction
achieved?
(Continued)

99. ARFF
6–99
Review Questions
4. Upon what variables does the
rate of application for fire fighting
foam depend?
5. What are the three basic
applications of high-expansion foam?
6. How does an installed in-line
eductor system work? (Continued)

100. ARFF
6–100
Review Questions
7. What is a handline nozzle?
8. How does the bank-down foam
application technique work?
9. What are the two basic designs
for handheld dry-chemical
extinguishers?
(Continued)

101. ARFF
6–101
Review Questions
10. Why are halogenated
extinguishing agents being replaced
by alternative agents?