“the science behind positive pressure attack”€¦ · “the science behind positive pressure...
TRANSCRIPT
“The Science Behind
Positive Pressure Attack”
Robin Zevotek, PE
Lead Research Engineer
IFV Conference
November 4th- 5th 2015
UL Firefighter Safety Research Institute
PPV Project Video
PPV Technical Panel
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FPO
• 26 Fire Service Professionals
• 4 Countries
• Over 500yrs combined fire service experience
Project Objectives
• Improve firefighter safety by increasing knowledge of fire behavior.
• Develop knowledge of positive pressure ventilation tactics.
• Identify and disseminate standard best practices for the use of positive pressure ventilation during fire attack based
on science.
• Generate understanding of modern construction practices such as open floor plans and great rooms on positive
pressure ventilation tactics.
• Bring the ‘Science to the Streets’ by transferring science based tactical considerations founded on experimental
results that can be incorporated into firefighting standard operating guidelines.
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Getting on the same page…
Positive Pressure Ventilation – The use of a high
powered fan to remove products of combustion from a
fire building, after the fire has been controlled.
Positive Pressure Attack – The use of a high powered
fan to control the flow of products of combustion, prior
to fire control, with the intent of providing increased
visibility and tenability for firefighters and potential
occupants while fire suppression efforts are underway.
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Reasons for Ventilation
Essentials of Firefighting
• Reduce Interior Heat Levels
• Decreasing Rate of Fire Spread
• Reducing Potential Extreme Fire
Behavior
• Improving Interior Visibility
• Improving Firefighter Efficiency
• Improving Potential Victim
Survivability
• Reducing Smoke Damage and
Property Damage
Officers Handbook of
Tactics
• To Allow attack teams to enter
and operate within the structure
(Venting for fire)
• To provide fresh air for breathing
(Venting for Life)
• To improve visibility while
searching (Venting for Life)
Positive Pressure Attack
for Ventilation and
Firefighting
• Assists with survival and rescue
of trapped victims
• Protects firefighters
• Aids firefighter entry
• Rapid advance to the seat of the
fire.
• Decreases fire spread
• Decreases property damage
How do we most effectively accomplish
ventilation to achieve these goals?
Test Fixtures
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Single Story
• 1200 Sq. Ft Ranch
• 3 Bedroom 1 Bathroom
• 8 Total rooms
Two Story
• 3200 Sq. Ft Colonial Style
• 4 Bedroom 2 Bathroom
• 12 Total rooms
• Open Floor Plan
Single Story
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Two Story – First Floor
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Two Story – First Floor
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DHS – 2012 Positive Pressure Attack
• 30 Cold Flow Experiments
Single Story & Two Story
• 25 Fire Experiments
- 15 Single Story
- 10 Two Story
• Over 500 Visitors during the experiments
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Yields:
• 72hrs of video (Post Processed)
• Over 2 Million Data Points
• 825+ Graphs
Experimental Procedure – Cold Flow
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Blind Selection from Panel Members based on flow results.
Any manufacturer was invited to send fans for blind selection
• Five Manufacturers Participated
• 12 Total fans (1 Gas and 1 Electric)
Fan Flow is Dependent Geometry of Structure
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Gas Fans – Front Door In-Flow Electric Fans – Front Door In-Flow
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Bigger is not necessarily better.
• Increased flow creates more
pressure.
• If ventilation openings are not
present in sufficient square
footage the pressure creates back
flow.
• Back flow allows the fire to burn
out of the compartment.
*Selected fan for fire experiments.
Flow is dependent on exhaust
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Gas Fans Electric Fans
Additional Exhaust Only Helps in the Fire Compartment
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Understanding inlet to outlet ratio
VS.
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VS.
Additional Exhaust Only Helps in the Fire Compartment
Understanding inlet to outlet ratio
Fan Set back has limited effect on flow
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Fan Set back has a significant effect on pressure
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Fan Set back has limited effect on flow
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Fan Set back has a significant effect on
pressure
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Unidirectional Flow can not be achieved at the front door. Flow at
the top of the inlet does not mean ineffective PPA, changing smoke
conditions in the structure indicate PPA effectiveness.
Door
Disclaimer goes here
• Neutral Plane
• Flow is not uniform in the exhaust or inlet
• Fan flow is not uniform
Unidirectional Flow can not be achieved at the front door. Flow at
the top of the inlet does not mean ineffective PPA, changing smoke
conditions in the structure indicate PPA effectiveness.
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An ongoing assessment of the inlet and exhaust is essential for
determining effectiveness.
Reading the inlet:
• Will not determine if fan is
properly placed.
• Takes time to indicate if interior
conditions are clearing.
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An ongoing assessment of the inlet and exhaust is essential for
determining effectiveness.
Reading the exhaust:
• Is more important than effective inlet.
• Can identify if sufficient flow is
established.
• Will not identify if too much flow is
provided.
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Unidirectional Flow can not be achieved at the
front door. Flow at the top of the inlet does not
mean ineffective PPA.
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Unidirectional Flow can not be achieved at the front door. Flow at
the top of the inlet does not mean ineffective PPA, changing smoke
conditions in the structure indicate PPA effectiveness.
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VS.
Understanding Flow through vs. Flow Out
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Understanding Flow through vs. Flow Out
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2
Understanding Flow through vs. Flow Out
Open Concept Presents Challenges to
PPA Effectiveness
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Open Concept Presents Challenges to
PPA Effectiveness
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VS.
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Creating additional openings, not in the fire room, will create
additional flow paths, making PPA ineffective with the potential to
draw fire into all flow paths.
Creating additional openings not in the fire
room will create an additional flow path making
PPA less effective.
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Fan On – 8:28
Flames Bed 1 – 10:28
Any opening decreases pressure and makes PPA less effective
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• Avoid VEIS?
Positive Pressure, Horizontal and Vertical Ventilation are
tactical choices. No one tactic will work in every scenario.
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Living Room
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Dinning Room Kitchen
Positive Pressure, Horizontal and Vertical Ventilation are
tactical choices. No one tactic will work in every scenario.
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Bedroom 1 Bedroom 3
Positive Pressure, Horizontal and Vertical Ventilation are
tactical choices. No one tactic will work in every scenario.
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Extension into the void spaces when using PPA is directly related to
the exhaust capabilities of the void space.
Metal Box
LightsSingle
Plastic
Switches
Single
Plastic
Outlets
Three
1 ½” Holes
5.3 in2
Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Outlets
Switches
Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Extension into the void spaces when using PPA is directly
related to the exhaust capabilities of the void space.
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Extension into the void spaces when
using PPA is directly related to the
exhaust capabilities of the void
space.
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PPA does not negatively affect the impact of being behind a
closed door.
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Systematic Ventilation
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
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Systematic Ventilation
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
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Non - Systematic Ventilation
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
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Non - Systematic Ventilation
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
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Non - Systematic Ventilation Systematic Ventilation
The more openings created during PPV the more effective it is
in ventilating the structure post fire knockdown.
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Non - Systematic VentilationSystematic Ventilation
Next Steps
• Complete data analysis
• Draft report
• Finish online training program
• Disseminate results
• Project Completion Date 8/2016
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Questions
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DHS – 2012 “Study of the Effectiveness of Fire
Service Positive Pressure Ventilation During Fire
Attack in Single Family Homes Incorporating Modern
Construction Practices”
