THE SCIENCE BEHIND FIRE
Fire is defined as a rapid persistent chemical change causing the release of light and heat accompanied by flame. In a controlled setting it is one of the basic necessities of life. When uncontrolled, it is a significant problem causing property destruction and loss of life.
Fire Tetrahedron
The latest research lists 4 required elements necessary to make and sustain fire. These include the 3 basics of Oxygen, Heat, Fuel along with a 4th element, a chemical or chain reaction. This reaction is a self-sustaining chemical response that produces continued heat that serves to keep the fire propagating/burning.
To help illustrate that these four elements must occur together in order for a fire to exist, the 4-sided pyramidal shaped tetrahedron model was developed. Remove any one of these elements from the fire tetrahedron and the fire will not start or, if already burning, will be extinguished.
Stopping a Fire
A burning fire is actually a chemical reaction that consumes fuel and oxygen to produce heat and light as byproducts. By removing any of the pieces of the tetrahedron, you break the chain and stop the chemical reaction and the fire is extinguished.
CLASSES OF FIRE
There are four categories or classes of fires. An understanding of what constitutes a class of fire is important so as proper fire and smoke containment procedures may be followed. The four classes are referred to as A, B, C, and D.
Class A Fires
Common carbon-based combustible products are considered class A. These include items such as wood, paper, cloth, rubber and plastics. If it leaves an ash when it burns, it is usually a Class A fire. Examples - Seats, carpet, trash, paper, catering trays. *Lithium Battery Fires (Portable Electronic Devices) have a class A element. How to extinguish a Class A fire: Large amounts of water to cool the fire, removing the heat.
Class B Fires
Flammable liquids including oils, greases, tars, oil-based paints, lacquers and flammable gases Examples- Cooking oil & grease, fuel How to extinguish a Class B fire: Blanket the fire to stop chemical reaction or separate the flame from the fuel.
Class C Fires
Energized electrical fire. May also contain elements of a class A fire. If the entertainment system fails, both A&C fires will be present. Examples - Lighting, entertainment systems, electronics, wire bundles How to extinguish a Class C fire: Non conductivity of extinguishing agent is important... No water! Chemical disruption is necessary to stop the fire.
Class D Fires
Fires involving combustible metals. Items containing magnesium, titanium, sodium, lithium, potassium to name a few. Examples- Brakes, wheels, hull, portable electronic devices. Lithium batteries also have a class D element. How to extinguish a Class D fire: Requires special extinguishing agents and techniques and requires special extinguishing agents and special techniques for effective abatement.
FAA ADVISORY CIRCULAR AC 120-80B
Subject: Firefighting of General and High-Energy In-Flight Fires
https://www.faa.gov/
documentLibrary/media/Advisory_ Circular/AC_120-80B.pdf
Inflight Fire and Smoke 4
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