Week 1 Seminar

Combustion Processes
(con’t from Unit 4)
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.
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
 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
 Its burning regime (ventilation or fuel
 Stage of burning throughout the structure.
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
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
 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!
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
Fire events
Rollover or flameover
Fire stages
Incipient or ignition stage:
 Occurs after ignition
 Flames are small and are contained within
material first ignited.
 No oxygen reduction (21%)
 Convection brings in additional oxygen
Fire stages
Growth stage:
 Fire grows in intensity and more fuel is
involved releasing additional energy.
 Increased fuel consumption and heat
 Heat carried up by convection and spreads
horizontally until reaching the walls.
Fire stages
Fully developed stage:
 After reaching walls, heated gases bank downwards into
lower portions.
 Heat is radiated which brings materials in the room up to
ignition temperature.
 Oxygen is reduced to 9 – 12%.
 Upper portions 1000 degrees F.
 If flashover occurs it is between growth and fully
developed stages.
 Hot temperatures but heat released slowed due to lack of
 Backdraft conditions may be present.
Fire stages
 Plenty of heat waiting on introduction of additional
 Proper ventilation can prevent/reduce backdraft.
Transfer of heat
Direct flame
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