Fire Behavior Understanding the Basics

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					     Fire Behavior
Understanding the Basics




           Pat Hultman FF/MICT/LEO-AAS
                   Training Officer
Learning Outcomes
• List different types of Extreme Fire
  Behavior
• Differentiate between Fuel and Air
  controlled fires
• Understand the importance of
  reading smoke and fire
• Appreciate the dangers assosciated
  in regards to extreme fire behavior
Why this matters
  • In 2007, 20 LODD due to Extreme
    Fire Behavior. Plus numerous close
    calls.




  Video 4.5 min. !!!1:41!!!
          Fire Tetrahedron
• Fire Triangle

• H2O??

• Combustion


        C6H12O6   + 6 O2   = 6 CO2   + 6 H2O
Flame Types
                Fuel State
• What Burns?

• So how does a
  solid burn?
  – Pyrolisis
         Fire Gases and Pyrolisis
• Common Fire Gases • Pyrolisis
  – CO                  – Decomposition by heat
  – HCN                 – ↑ build up of combustible
  – Hydro Carbons         gases
     • Methane          – Where does the heat come
     • Propane            from?
Heat Transfer
• Conduction
  – Direct transfer through contact
• Convection
  – Transfer through a medium such as air,
    H2O, etc
• Radiation
  – Transfer in the form of light energy
            Understanding Radiant Heat
• Is radiant heat visible?     • Direct Summer Sun
• At 900° F visible                – 1kw/m² 100° F Surface
                                        • No Pain
                               • Near Proximity to Fireplace
• Heat Release Rate
                                   – 10kw/m² 200-300° F Surface
   – Cigarette 5w                  • 2° Burns ≤ 10Sec
   – Wastebasket 50-150 KW         • Scorching of and Melting of
   – Pool of Gasoline (2 QTS) • Adjacent to flames
     1MW
                                – 50 kw/m² 800° F Surface
   – Sofa 1-3 MW
                                – Autoignition of nearly all
                                  materials in ≤ 5 sec

                                 The avg residential fire will double in size
                                 every 15-30 secs
Limits of Flamability
• LFL/UFL

• What are some materials you can think of?
     •   Propane 2.1-9.5% Ideal 4%
     •   Gasoline 1-6%
     •   Acetylene 2.5-80%
     •   CO 12.5-74% What is this in PPM (move decimal
         right add 3 zeros)


• Think about the CGI
  – We know we are immersed in flammable
    gases when going into a fire
Smoke is Fuel




                Smoke
                Video
Smoke is Fuel
The Neutral Plane
• Two Separate Layers
  – Hot Buoyant Combustible gas
    • Major source of radiant heat
  – Cooler, cleaner


• Commonly discussed as thermal
  layering (Discussed More Later)
       Fire Progression
• Stages of Fire
  – Phase 1                          – Phase 3
     • Incipient and Growth             • Fully Developed
       Stage
         – What is happening?
                                     – Phase 4
         – What is the next
           phase?                       • Decay Stage
  – Phase 2
     • Flashover                  • What is a significant
     • What happened?               threat at this stage?
     • Auto-ignition temp
         – What is the
           significance?
              » Transition From
                Room and
                Contents
    Extreme Fire Behavior
These are not some strange uncontrolled phenomenen.
There are key things to watch for both inside on the knob and
outside as IC.


• Smoke Explosion                  • Fire Gas Ignitions
• Flame Over                       • Flashover
• Flash Fire                       • Back Draft



                                  The Firefighter must remain ever
                                  vigilant of the conditions around them
Flashover
• Sudden and Sustained transition from
  a developing fire to a fully developed
  fire.

• 2/3rds of the heat is radiated down
  from the neutral plane



                                   Video 1:01
       Signs and Symptoms of
              Flashover
•   Ventilated Fire
•   Painful Radiant Heat (forces you down)
•   Hot Surfaces (Conduction)
•   Lowering Neutral Plane
    – Fingers of flame – Dancing angels
• Increased Pyrolisis
• Increased turbulence of smoke and flame
Back Draft
• The spontaneous ignition of
  combustible fire gases.
• What are some cause? Why?
  – Gases at auto ignition temperature
  – Lack of Oxygen
  Pyrolisis will continue to occur until
    sufficient cooling



                                Video 0:44
     Signs and Symptoms of
           Back Draft
• No or limited ventilation
• Lack of visible or blue flame
• Thick rolling black, yellow, or white
  smoke
• Smoke Pulsating/Whistling
Point of No return
• 5 feet (Chief Dunn)
• Burns
  – 1° @ 118° F
  – 2° @ 131° F
  – 3° @ 152° F

       – Heat Output
          » Trash Can Fire
Methods of Extinguishment
• Direct vs. Indirect
   – Smooth Bore vs. Fog
• Gas Cooling
   – Can disrupt neutral plane
   – Use small fine droplets in short bursts to
     minimize

          – How much water in GPM for a 19x16 MBR
              » 300 ft² approx
              » Round Up to 375 ft² or 3000 ft³ for chart
              » NFA- 125 GPM
              » Iowa – 30 GPM
              » 3D- 75 GPM
Case Study
•   April 16 2007
•   24 Y/O Kyle Robert Wilson 2 yrs exp.
•   0604 AM
•   Weather- 25 MPH sustained

				
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posted:12/11/2011
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