2. 8
Learning Objectives (1 of 15)
• Compare an offensive fire attack to a
defensive fire attack, explaining the
basics of each type of attack and
identifying the rationale for each
strategy.
• Describe trial-and-error methods of
calculating rate of flow.
3. 8
Learning Objectives (2 of 15)
• Explain the theory of indirect
extinguishment.
• Compare conditions within a fire
compartment after pulsing versus after
an indirect attack.
4. 8
Learning Objectives (3 of 15)
• Analyze rate-of-flow requirements using
V/100, A/3, and sprinkler calculations.
• Define a ventilation-controlled fire.
• Define a fuel-controlled fire.
5. 8
Learning Objectives (4 of 15)
• Describe “area of involvement” and how
it applies to rate-of-flow calculations.
• Write a brief position paper outlining the
advantages of using the Royer/Nelson
(V/100) rate-of-flow formula.
6. 8
Learning Objectives (5 of 16)
• Explain why a fire attack meeting or
exceeding the calculated rate of flow
could fail to extinguish the fire.
• Explain the relationship between nozzle
type, rate of flow, and nozzle reaction
force.
7. 8
Learning Objectives (6 of 15)
• Discuss the advantages and
disadvantages of using an aerial device
as a portable standpipe.
• Describe extinguishment of ordinary
combustibles by inhibiting pyrolysis.
8. 8
Learning Objectives (7 of 15)
• Discuss the dangers of opposing fire
streams and ways to avoid opposing fire
streams.
• Define external exposure.
• Define internal exposures.
• List factors to consider when evaluating
external exposures.
9. 8
Learning Objectives (8 of 15)
• Describe the purpose of a backup line
and how it can be used to protect fire
fighters attacking the fire.
• Evaluate water supply requirements
based on rate of flow and other factors.
10. 8
Learning Objectives (9 of 15)
• Examine the relationship and proper
use of ventilation during offensive
extinguishment operations.
• Describe the factors that determine the
number of apparatus needed at an
offensive operation.
11. 8
Learning Objectives (10 of 15)
• Discuss apparatus management at a
medium- to large-scale incident.
• Develop a list of advantages and
disadvantages when using Class A
foam during structural firefighting.
12. 8
Learning Objectives (11 of 15)
• Compute and compare the rate of flow
for various areas using A/3 and V/100.
• Evaluate the available flow from
standard pre-connected hose lines and
determine when the rate of flow for a
structure should be pre-incident
planned.
13. 8
Learning Objectives (12 of 15)
• Estimate the number and size of hose
lines needed to apply a calculated rate
of flow.
• Assess staffing requirements for an
offensive attack based on rate-of-flow
and life safety factors.
14. 8
Learning Objectives (13 of 15)
• Assess the probability of an imminent
life-threatening situation.
• Compare staffing available to staffing
requirements.
15. 8
Learning Objectives (14 of 15)
• Using a fire scenario, assess the total
water supply available and apparatus
needs in terms of required fire flow.
• Given fire conditions and location,
determine the ventilation possibilities
and choose the best ventilation
method(s).
16. 8
Learning Objectives (15 of 15)
• Evaluate the flow available from a
standpipe system and standard fire
department standpipe equipment based
on a calculated rate of flow.
• Examine and evaluate various attack
positions in a multi-story building.
• Discuss factors involved in choosing an
offensive strategy.
17. 8
Overview
• Offensive versus defensive fire attack
– Based on staffing levels and risk–benefit
analysis
• Rate-of-flow
– Determines number and size of hose lines
• Resource capabilities must meet
incident requirements
18. 8
Calculating Rate of Flow
• Methods
– Clark’s calculation
– Trial and error
– Royer/Nelson formula
– National Fire Academy formula
– Sprinkler calculations
• Cannot predict every variable
19. 8
Indirect Application
• Lloyd Layman
– Coast Guard tests
– Based on water converting to steam
– Reduced water use = less property
damage
– Disrupts heat balance
• Decreases chances for occupant survival
• Increases chances for fire fighter steam burns
20. 8
Royer/Nelson Formula (1 of 2)
• V/100 = Volume in cubic feet divided by
100
• Oxygen controlled fires
– Require less water
• Valid for most fires
– Accounts for ceiling heights
• Recommended for pre-planning
22. 8
NFA Formula (1 of 2)
• A/3 = Area in square feet divided by 3
• More conservative and less accurate
• Yields a higher rate of flow in most
situations
• Recommended for scene use
24. 8
Sprinkler Calculations (1 of 2)
• Most accurate
• Considers fuel load and type
• Useful in pre-planning
• Published in NFPA documents and
Factory Mutual Data Sheets
• NFPA 13: Standard for the Installation
of Sprinkler Systems
25. 8
Sprinkler Calculations (2 of 2)
• Variables:
– Building type
– Number of floors
– Occupancy type
– Commodity inside the structure
– Storage configuration of the commodity
26. 8
Stages of Fire
• Early stages: fuel dependant
• Late stages: oxygen dependant
• Well involved fires controlled by both
• Once ventilated, fire reacts to type and
amount of fuel.
27. 8
Estimating Compartment Size
• Rate-of-flow based on area or volume of
compartment(s) on fire
• Calculating each area separately is
recommended.
– Provide flow needed for largest area.
• Fire fighters can estimate size for IC.
28. 8
Pre-Planning by Occupancy
• One- and two-family dwellings
• Apartment buildings
– Common areas
• Small businesses
29. 8
Estimating Percent of Area on
Fire
• Royer/Nelson
– Volume of enclosure
– Doesn’t consider modifying formula
• NFA
– Area of involvement
– Percentage-of-involvement modifier
recommended
30. 8
Comparing Rate-of-Flow
Calculations (1 of 2)
• Sprinkler calculations, variables:
– Building type
– Number of floors
– Occupancy type
– Commodity
– Storage configuration
• Most accurate
• Based on actual fire experience
31. 8
Comparing Rate-of-Flow
Calculations (2 of 2)
• U.S. National Fire Academy system
– Yields higher rate of flow
– Field-estimated
– Overestimation leads to quicker
extinguishment with less water
– Gross overestimation may cause a delay in
attack
32. 8
Which Rate-of-Flow
Calculation Is Best?
• Each method has merit.
• If fuel load is heavy, sprinkler
calculations should be used.
• A/3 formula may be easier, but may not
be as accurate.
• Each formula must be modified based
on trial and error.
33. 8
Selecting Attack Hose Size
• Booster hose inappropriate for structure
fires
• 1¾” (44-mm) attack hose lines
recommended as a minimum
– With backup hose line, will be adequate to
extinguish most fires
• Mobility decreases, flow increases with
2½” (64-mm)
34. 8
Nozzle Flow Rates
• Flow rates vary according to:
– Nozzle pressure
– Pump discharge pressure
– Length of hose lay
35. 8
Nozzle Flow Ratings
• Variable-stream nozzles rated by:
– Pump discharge pressure and the length of
hose, or
– Nozzle pressure
• Smooth-bore nozzles rated by:
– Nozzle pressure
37. 8
Nozzle Reaction Force
• Increases as the flow and nozzle
pressure increase
• Makes nozzle more difficult to control
• If reaction force is too great:
– Flow should be reduced
– Nozzle should be replaced with one that is
easier to control
38. 8
Portable Standpipes
• Aerial ladder
– Limited to height of ladder
• Pre-piped waterway
• Pressures supplied by apparatus pumps
– Eliminates potential standpipe problems
• Can be used in buildings not standpipe
equipped
39. 8
Nozzle Selection
• Variable-stream versus smooth bore
• Stream force
– Affects the distance the stream will carry
– Allows the crew to access hidden fires
• Fog streams
– Stop forward extension of fire
– Provide exposure protection
40. 8
Selecting Stream Position (1 of 3)
• Indirect attack
– Little application to structural firefighting
– Steam production is dangerous
• Poor choice in occupied areas
– Useful in unoccupied basements, attics, or
storage areas
– Piercing nozzles
41. 8
Selecting Stream Position (2 of 3)
• Direct attack
– Preferred
– Applies water directly on the burning
material
• Reduces temperature of the fuel
• Reduces or eliminates combustible vapors
42. 8
Selecting Stream Position (3 of 3)
• Combination attack
– Direct and indirect application
– Dangerous for interior application
• Disturbs heat balance
• Generates intense steam
45. 8
Hose Line Placement
• Risk-versus-benefit analysis
• First line should be placed between the
victim and the fire.
– Coordinated with entry and ventilation
• Objective is to get water directly on the
fuel.
46. 8
Number of Attack Lines
• Based on flow requirements
• A single 1¾” (44-mm) hose line for most
dwelling fires
• Backup hose line
– Protects egress routes
– Bolsters attack
47. 8
Evaluating Exposures
• Internal
– Natural pathways
• Concealed spaces, stairs, chutes, and shafts
• Vertically up the exterior of the building from
windows or other openings
48. 8
External Exposures (1 of 2)
• Adjacent buildings
• Improper ventilation can expose
buildings.
• Consider fire apparatus and equipment
parked near the fire building.
50. 8
Factors to Consider
• Proximity to the fire building
• Wind direction
• Height of exposure
• Life hazard in the exposure
• Hazard presented by the exposed
occupancy
51. 8
Backup Lines
• Protect the crew on the initial attack line
– Also provide additional flow if needed
• At least as large as the initial attack line
52. 8
Additional Lines
• To meet the rate of flow in the
immediate fire area
• Backup hose line(s) for immediate fire
area
• To protect egress routes
• To protect internal/external exposures
• Other backup hose lines as needed
53. 8
Water Supply Needs
• Large diameter hose effective
• Two supplies recommended
• Shouldn’t rely solely on water tank
supply
• Must supply calculated rate-of-flow
– Plus backup/exposure lines
54. 8
Ventilation Needs
• Used to assist in extinguishment efforts
– Allows approach to fire
– Controls fire spread
– Makes conditions tenable
• Venting to support extinguishment
– Timing is crucial
– Charged lines must be in place
• Improper venting can extend fire
55. 8
Staffing Needs
• Based on:
– Rate of flow
– Backup lines
– Placement of lines above the fire
– Secondary water supply
56. 8
Initial Response
• NFPA 1710
– Defines tasks and minimum staffing for the
initial response
– If needs not met, must call for mutual aid or
additional alarms
57. 8
Apparatus Needs
• Normally sufficient for initial response to
offensive operation
• Proper positioning crucial
• Use only those necessary to meet tactical
objectives.
• Large scale incident or staging area
– Staging officer
– Staged apparatus: staffed
– Out of service apparatus: not staffed
58. 8
Class A Foam (1 of 2)
• Wildland and wildland/urban interface
uses:
– Pre-wetting fuels
– Providing a foam layer on an exposure
• Reduces radiant heat absorption
– Suppression agent
– Wetting agent
• Resulting in greater penetration
59. 8
Class A Foam (2 of 2)
• Useful in areas with a marginal water
supply
• Less water damage because less water
is used
60. 8
Summary
• Considerations for a safe and effective
offensive operation
– Sufficient personnel and resources:
• to deliver the required rate of flow
• to protect the fire fighters
• Rate-of-flow formulas
– Most valuable when included in pre-plans
– V/100 or sprinkler charts used in pre-plans
