Training Document: Fire Dynamics
Firefighting services have extended to the community nowadays as opposed to what the situation was in the past. Firefighters need to have in-depth knowledge about dynamics that applies to their area and location of work. Madrzykowski (2013) defines fire dynamics as the study on the start, spread, development, and extinguishing of the fire. This training document outlines fire combustion, evolution, classification, spread, emergency, and behavior relevant to beginner firefighters in the community.
Fire Combustion
Fire combustion requires fuel, heat, and oxygen, a relationship demonstrated by the fire triangle (Madrzykowski, 2013). The combustion process requires gaseous reactants; thus, fire is produced when a fuel is heated to a gaseous state, or it releases gases. The hot gases dissociate and combine with oxygen in the air to form carbon dioxide and water molecules depending on the amount of oxygen. Fire occurs when the hot dissociated gas molecules combine with oxygen causing burning (Madrzykowski, 2013). Fire spread occurs due to the ignition of the emitted gases in the presence of oxygen. The chemical chain reaction continues in the availability of fuel and oxygen.
The combustion chain reaction is, fuel + oxygen = CO2 + H2O + heat energy.
Stages of Fire Evolution
The International Fire Service Training Association (IFSTA) identifies the following as stages of fire evaluation:
- Incipient stage: This is the ignition stage where the combination of fuel, oxygen, and heat causes a fire. The small fire is often extinguished before it spreads.
- Growth stage: The fire load of the structure and oxygen acts as fuels for the fire. Flashovers are likely to occur at this stage and trap, injure or kill firefighters.
- Fully Developed Stage: At this stage, the fire has ignited all combustible substances. It is the hottest and most dangerous phase of fire development.
- Decay Stage: At this stage, oxygen or fuel decreases ending the fire. Re-ignition may occur if oxygen is reintroduced or non-flammables are not fully extinguished.
Classifications of Fire
- CLASS A: These fires involve ordinary combustibles such as paper, plastics, wood, rubber, or cloth.
- CLASS B: These involve flammable gases and liquids such as oil, paint, petrol, or tar.
- CLASS C: These are electrical fires from wiring, motors, or appliances.
- CLASS D: Fires involving burnable metals such as sodium or magnesium.
- CLASS K: These fires originate from burnable cooking appliances in the kitchens.
Fire Emergency
The awareness of fire classes influences the installation of capable fire safety equipment during fire emergencies and accidents. For instance, Class D fires are extinguishable by dry powders, Class B by smothering, while Class A with water. Thus, fire classification is essential in the choice of extinguishers during a fire emergency. The knowledge of fire evolution also influences the emergency response to fire incidents. Reorganization of fire at the incipient stage increases the chances of escape or suppression. Besides, analyzing factors influencing the growth stage, such as adjacent combustibles, source of fire, and ceiling heights, impacts extinguishing procedures.
Factors of Fire Spread and Behavior
Fire behavior encompasses flame ignition, fire development, spread, and other factors that influence the process (US Forest Service). The elements of fire spread are topography, fuels, and weather, as in the fire behavior triangle.
- Topography: Fires spread faster uphill thus;, topography affects the process of heat transfer even in structures.
- Fuels: These are anything burnable. They exist in wildlands and structures as wood or petroleum products. The fuel characteristics are responsible for different fire behaviors.
- Weather: This affects the intensity, size, or severity of the fire. Wind increases oxygen to the fire, while temperature and precipitation influence fuel properties that affect the spread and behavior of fire.
References
Madrzykowski, D. (2013). Fire Dynamics: The science of fire fighting. International Fire Service Journal of Leadership and Management, 7, 1–76.
The International Fire Service Training Association (IFSTA). Retrieved May 05, 2020, from https://www.ifsta.org/
US Forest Service, Wildland Fire. (n.d.). Retrieved May 05, 2020, from https://www.fs.usda.gov/managing-land/fire