Full Fire Fighting & Fire Protection Course - (Part 2)

         This is the 2nd part of this fire fighting and fire protection full series. You can access the previous parts, by clicking on the links provided at the end of this post. In this part, we will learn about the Classification of Fire.

Classification of Fire

The classification of fire in buildings is the classification of the type of building materials, design, location, construction condition, occupancy, and use. These factors determine how much time it takes for a fire department to arrive at a site, how fast they respond, and what tactics they employ. In order for the fire department to know where to deploy their firefighters safely, they need to know the type of building being constructed. A classification system is also valuable to determine if the structure is safe before firefighters enter.

Fire classification refers to how a building will burn once ignited. There are three types of fires that we are going to cover. They are Flammable materials fire, Structural collapse fire, and Toxic/poisonous fire.

Flammable Materials Fire

In the flammable material fire, a fire starts due to the ignition of flammable material. These materials can be anything from furniture, curtains, papers, plastics, chemicals, aerosols, etc. Typically, these are small fires and burn themselves out relatively quickly, unless they start in confined spaces where ventilation is difficult.

Structural Collapse Fire

This type of fire occurs when a structure fails under its own weight and collapses. The failure may occur from a structural point (e.g., foundation failure), design (e.g., lack of adequate bracing, insufficient shear wall thickness, inadequate roofing system) or construction (e.g., improper installation). In any case, the result is the same-a loss of containment and subsequent rapid spread of fire.

Toxic/Poisonous Fire

A toxic/poisonous fire is caused by the release of toxins-either intentionally or accidentally into the environment. A chemical fire is an example of a toxic/poisonous type of fire. Toxic/poisonous fires are more challenging than other types of fires because they can be fueled by virtually any combustible material. If a toxic/poisonous fire starts indoors, the effects of exposure can range from mild illness to death. Toxicity is determined more by the composition of the released substance than by the quantity.

1. Class A fires

A class A fire is defined as any building where there is not a sprinkler system installed. In some states they can still be classified as a class B or C depending on how small the area of the building is. In general, if the fire department calls out for a class A fire, then there should be no water damage and no damage at all. If the first responders have trouble getting inside and seeing what exactly happened, then there could be some minor damage. However, if the fire is strong enough and spreads fast, then there may be severe damages or even loss of property.

This type of fire is caused by combustible materials, such as paper, wood, textiles, plastics, rubber, etc., which have been subjected to ignition, either deliberately or accidentally. These materials continue to burn until they produce sufficient oxygen (usually about 30 minutes) to consume all the fuel completely. When combustibles reach this point, they are said to be burning at a steady rate.

2. Class B fires

Fire may ignite spontaneously if a material contains volatile compounds that promote combustion. Common examples of these types of fires are natural gas leaks, electrical short circuits, chemical reactions, spontaneous autoignition of mixtures containing flammable liquids, etc. In cases where a fire starts spontaneously, it is not immediately apparent what started the fire. This type of fire burns slowly and continuously until the fire reaches self-sustaining conditions.

                This type of fire requires sprinklers and it happens when the sprinkler system is not working correctly or is not present. When using a sprinkler system, there is an advantage to having them installed in a way that only covers certain areas of the structure. Not doing so means that the rest of the ceiling is open to the flames. If the sprinkler system does work correctly, then there should be minimal damage and water will flow down, but the amount that exits should be able to put out fires relatively easily.

3. Class C fires

These fires are normally associated with a person's carelessness. There is no doubt that the origin of the fire was human action. However, the fire could start without any prior indication of danger. Firefighters often say, "It looks like someone forgot to turn off the stove." Or, "It looks like an accident." Such fires burn slowly and continuously until they reach self-sustaining levels.

                    In this case, the fire is contained to a specific space in the building. In order to use a sprinkler system, the location of the fire needs to be known before it starts. Once the fire is started, the sprinkler system will go off, putting out the fire. If the location of the fire is not known, then using spray foam or a similar product will help prevent the fire from spreading to other parts of the building.

4. Class D fires

The cause of this fire is unknown. It is unlikely that the fire would have occurred without human activity. Often, firefighters cannot determine the specific cause of a fire.

Classical fire classification systems were designed to identify the type of fire that caused the greatest amount of damage and loss of life. This system does not apply well to modern building construction methods. Modern buildings do not generally use traditional materials; therefore, they do not burn as easily as older structures did. Modern building codes require that all exits be clearly marked and accessible. Also, most people are trained to exit the structure safely in order to prevent major injury or death. Unfortunately, some fires still occur due to negligence or faulty design.

5. Class K fires

The classification of a fire is determined by its intensity. The two classes of Fire Classes are A and B. Class A fires have an average intensity of greater than 1,000 calories per square foot of surface area. Class B fires have an average intensity less than 500 calories per square foot of the same surface area. Class C fires are those that are between 400-999 calories per square foot. Fire Class K represents the lowest intensity fire, which burns at an intensity less than 400 calories per square foot. (This is also known as Low Intensity Flame.)

2. Class K Fire

There are three types of low intensity fires (Class K) that are classified according to their use:

(a) Propane

(b) LPG

(c) Liquid petroleum gas (LPG)

Propane/gasoline/diesel engines do not start with very little fuel. Typically, these fuels require a minimum amount of 9-10 gallons of fuel to get a good flame going. These fires burn very slowly and normally are lit after dark. When the spark plug of the engine is removed, the fire dies out. They should only be lit outside if the temperature is below freezing and if weather conditions are windy.

For a propane tank to explode it requires a pressure buildup of about 3 psi over an extended period of time. There are several ways to prevent this explosion:

(a) Properly store containers of propane away from any flammable material;

(b) Store containers above ground to allow air circulation around them;

(c) Use a vent cap on top of the container to release excess pressure.

In addition, some users may choose to purchase smaller tanks and refill them frequently to avoid having to go to the trouble of purchasing larger tanks.

1. Fire Type 1

Fire type 1 is classified as a primary fire event. These fires occur when flammable materials ignite due to contact with other combustible substances, sparks, flames, or high temperatures. Such events commonly happen in enclosed spaces such as apartments and offices. Common causes for these types of fires include smoking cigarettes, cigars, pipes, or chewing tobacco; using lighters, matches, or lighter fluid; cooking food on hot plates or ovens; and smoking marijuana indoors.

2. Fire Type 2

Fire type 2 is classified as a secondary fire event. These fires start after a primary fire event has occurred. Typically, fires of this type are caused by the spontaneous ignition of highly flammable material such as gasoline, kerosene, or diesel fuel. Spontaneous combustion is a type of fire where a substance (usually a liquid) spontaneously ignites due to decomposition, oxidation, heating/cooling cycles, or just plain old exposure to oxygen.

3. Fire Type 3

The third type of fire occurs after fire type 2 has started. Fire type 3 is often referred to as a tertiary fire event. It is caused by electrical arcing between two conductors. This type of fire is called arc flash, or arc blast, and is extremely dangerous. Arc flash occurs when electricity strikes certain metals at high voltage, causing them to release oxygen molecules. These oxygen molecules then combine with charged particles to create a spark. If the sparks touch or strike anything flammable (like air), the result is a fire.

Access all the previous parts of this full fire fighting series by clicking the links provided below:

Part 1 --- Click Here!!!