TN 106.4- Flow Path and Door Control Part 1

Fire Fighters Guidance Note

• Fire departments should develop training in fire dynamics for suppression personnel to understand compartment fire behavior and rapid fire progression events. (Guidance Note #6-6).

History of Firefighting

• Firefighting has been a process of trial and error for over 200 years, with varying results.
• Upgrades in firefighting equipment and changes in building construction have made it necessary to study the science of fire.

Fire Dynamics

• Fire dynamics is the study of how fires start, spread, and develop.
• Understanding fire dynamics assists operations firefighters in developing strategies and tactics when responding to a fire incident.

Importance of Fire Dynamics

• Knowledge of fire behavior helps firefighters understand potential hazards and catastrophic fire events.
• Recognizing these events early aids in mitigating contributing factors and deciding to continue with a tactic or retreat.

Modern Construction Materials

• Modern construction materials and methods contribute to fires of higher energy and greater potential for structural compromise.
• Knowing the building profile and fire progression helps arriving crews develop a strategy or tactic.

UL/NIST Studies

• Studies from UL/NIST applied various firefighting practices in acquired structures to determine measurable results.
• These results, combined with fire dynamics, have greatly improved understanding of fire progression and behavior.

Firefighter Safety

• Firefighters armed with a basic knowledge of fire dynamics will be more effective and safer on the fireground.

Fire Dynamics Definitions

• Fire: a rapid oxidation process, resulting in the evolution of light and heat in varying intensities.
• Heat Energy: a form of energy characterized by vibration of molecules, capable of initiating and supporting chemical changes and changes of state.
• Temperature: a measure of the degree of molecular activity of a material compared to a reference point.
• Heat Release Rate (HRR): the rate at which fire releases energy, measured in Watts (W), Kilowatts (kW), or Megawatts (MW).
• Heat Flux: the rate of heat energy transferred per surface unit area, measured in kW/m2.
• Heat Transfer: a major factor in the ignition, growth, spread, decay, and extinction of a fire, always transferred from hotter to cooler objects.

Heat Flux Examples

• Sunny day: 2.5 kW/m2
• Typical firefighter exposure: 3-5 kW/m2
• Pain to skin within seconds: 20 kW/m2
• Threshold flux to floor at flashover: 84 kW/m2
• Thermal Protective Performance Test (NFPA 1971): 60-200 kW/m2

Heat Transfer Modes

• Conduction: heat transfer within solids or between contacting solids.
• Convection: heat transfer through natural movement of gases or liquids from higher pressure areas to lower pressure areas (buoyancy).
• Radiation: heat transfer by electromagnetic waves.

Fire Phenomena

• Fire Development: a function of many factors, including fuel properties, fuel quality, ventilation, compartment geometry, location of fire, and ambient conditions.

Learn about the importance of fire dynamics training for fire suppression personnel, including understanding modern contents' combustibility and its impact on compartment fire behavior.