2.3 Fires In The Workplace
D.M. Donner
The Chemistry of Fire
Before we can discuss fire safety awareness in the workplace, you first need to understand how fire works. The process referred to as a fire is more accurately defined as combustion. Combustion is the process of combining a fuel and oxygen and then adding an ignition source. Once you have those three elements in the proper proportion, the end result is fire. Fire, like a three-legged stool, will fail if you remove one of the supporting elements. Fuel provides the base substance which, when heated enough, breaks down into molecules, releasing gaseous energy which then ignites, creating heat and light. Heat is the energy that must be maintained to sustain the chemical breakdown of the fuel, providing the base for combustion. The final side of the fire triangle is oxygen which reacts with the fuel molecules that break apart and combine with other atoms and molecules.
To extinguish a fire, you will need to remove one of the three key elements: fuel, heat, or oxygen. This is performed by different processes depending upon the fuel or ignition present. Fuel and ignition define what classification of fire it is. Classes of fire will be discussed later.
Classifications of Fire
Fires are classified into different categories based on the type of fuel involved. The classification system helps explain the nature of the fire and determines the appropriate firefighting methods and extinguishing agents to be used. The most commonly used classification system is the one developed by the National Fire Protection Association (NFPA) in the US which categorizes fires into five classes (O’Connor, 2023).
Class A: These fires involve ordinary combustible materials, such as wood, paper, cloth, rubber, and some plastics. These fires typically leave behind ash after combustion. Class A fires are extinguished using water, which cools the fuel and removes heat from the fire triangle.
Class B: Class B fires involve flammable liquids or gases, such as gasoline, oil, grease, propane, butane, and certain paints and solvents. These fires are characterized by their ability to spread rapidly and may produce large flames or explosive conditions. Class B fires are extinguished using foam, carbon dioxide, or dry chemical agents that smother the fire and eliminate the oxygen supply.
A flammable liquid is any liquid having a flashpoint at or below 199.4 °F (93 °C).
As per its standard on flammable liquids (OSHA, 1970a), the OSHA Office of Training and Education (n.d.) states:
It should be mentioned that flash point was selected as the basis for classification of flammable liquids because it is directly related to a liquid’s ability to generate vapor, i.e., its volatility. Since it is the vapor of the liquid, not the liquid itself, that burns, vapor generation becomes the primary factor in determining the fire hazard. (p. 3)
Class C: Fires in this class involve energized electrical equipment, such as electrical appliances, wi