Combustion Processes (con’t from Unit 4) Unit 6 Seminar

Objectives Discuss the B-SAHF model and what each letter stands for. Explain B-SAHF model for each phase of fire development and the use of the model for each phase. Discuss if the students think this is a useful tool for teaching fire dynamics to fire service professionals.

Review from Last Week (Chapter 3) Combustion/Fire Fire Triangle Fire Tetrahedron Pyrolysis Smoldering/Flaming Combustion CO Fire Classifications Stages Ignition Growth Fully Developed Decay Flashover Backdraft Compartmentation Heat Transfer

From Unit 4 Assignment

Traditional Fire Behavior

Typical Fire Behavior?

Fire Dynamics The detailed study of how chemistry, fire science, and the engineering disciplines of fluid mechanics and heat transfer interact to influence fire behavior. NFPA 921 Guide for Fire and Explosion Investigations, 2008 Edition

What is B-SAHF? Acronym used to help size up critical fire behavior indicators. Consists of the following: Building Factors Smoke Air Track Heat Flame

Let’s discuss each critical factor! Building- Can be pre-planned to determine fire loads Fuel packages* Inventory fire behavior indicators present before a fire begins Construction and features Will help determine fire behavior and spread

Smoke, the second critical factor Along with air track the two most important indicators of fire behavior. Provides valuable cues as to the location of fire. Its burning regime (ventilation or fuel controlled*). Stage of burning throughout the structure.

Conshohocken,PA August 2008

Ventilation-Controlled Fire A fire in which the heat release rate or growth is controlled by the amount of air available to the fire. “Ventilation-Limited Fire”

Fuel-Controlled Fire Fire in which the heat release rate and growth rate are controlled by the characteristics of the fuel, such as quantity and geometry, and in which adequate air for combustion is available. “Fuel-Limited Fire”

Air Track and its impact Observe air movement from outside and continue while on the interior. Watch how smoke changes with fluctuations in the air track. Make air tracks work for you not against you!

Heat While heat cannot be observed directly, observe its effect on air track (i.e. velocity of smoke discharge), the building or exposures, and sensation of changes in temperature. Can be a significant fire behavior indicator It is important to remember that our personal protective equipment provides significant insulation and slows the transfer of heat and resulting sensation of changes in temperature.

Flame, the visible part! The most visible part of the B-SAHF model. Do not get so focused on visible flames that you miss important, but subtle building, smoke, air track, and heat indicators! Flame indicators such as location, volume, color, etc. provide help more complete picture but must be integrated with other factors to see the big picture!

B-SAHF for each phase Model can be used for each phase of fire. Get your reading assignment from Fire Growth and Development http://cfbt-us.com/pdfs/FBIandFireDevelopment.pdf Turn to page 4 and let’s review the phases and the application of B-SAHF.

Charlie House Bravo Delta Alpha Street

Other parts of the puzzle Ventilation controlled fires Operations conducted by firefighters can cause a ventilation controlled fire to enter back into the growth phase. Firefighters can be caught in vent induced extreme fire behavior. Watch the B-SAHF indicators to help recognize signs of impending extreme fire behavior.

Fuel Package A single burning item or object exposed to heat transfer resulting from a fire is referred to as a fuel package. Fuel packages can be comprised of a single fuel (e.g., wood, plastic) or they may be composites of a number of different materials (e.g., upholstered chair, sofa, or mattress).

Approximate Peak Heat Release Rates Burning cigarette 5 W  Burning match 80 W Burning coffeemaker 40 kW Small Trash Can, Trash Bag Fires 50 to 300 kW Burning Upholstered Chair 80 kW to 2.5 MW Burning Upholstered Sofa 3 MW to 5 MW Burning Christmas Tree 1.6 MW to 5.2 MW

Is it useful? How do you feel as a class after reading and reviewing the B-SAHF model? Is it a useful tool to train fire service professionals?

To Do… Review Key Terms Read Fire Growth and Development Attend the Weekly Seminar Respond to the Discussion Board Complete and Submit the Unit 6 Project Take the Self-Check Quiz Check out Extra! Extra!