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

– CO– HCN– Hydro Carbons

• Methane • Propane

• Pyrolisis– Decomposition by heat– ↑ build up of combustible

gases– Where does the heat come

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?• At 900° F visible

• Heat Release Rate– Cigarette 5w– Wastebasket 50-150 KW– Pool of Gasoline (2 QTS)

1MW– Sofa 1-3 MW

• Direct Summer Sun– 1kw/m² 100° F Surface

• No Pain

• Near Proximity to Fireplace– 10kw/m² 200-300° F Surface

• 2° Burns ≤ 10Sec• Scorching of and Melting of

• Adjacent to flames– 50 kw/m² 800° F Surface– 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• Incipient and Growth

Stage– What is happening?– What is the next

phase?

– Phase 2• Flashover• What happened?• Auto-ignition temp

– What is the significance?

» Transition From Room and Contents

– Phase 3• Fully Developed

– Phase 4• Decay Stage

• What is a significant threat at this stage?

Extreme Fire Behavior

• Smoke Explosion• Flame Over• Flash Fire

• Fire Gas Ignitions• Flashover• Back Draft

The Firefighter must remain ever vigilant of the conditions around them

These are not some strange uncontrolled phenomenen.

There are key things to watch for both inside on the knob and outside as IC.

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 OxygenPyrolisis 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