[National Qualifications You Can Aim For Even in Your 70s (11)] Fire Extinguishing Methods for Hazardous Materials and Types of Extinguishing Agents
We have learned about the types and properties of Class 4 hazardous materials so far.
This time, we will explain the fire extinguishing methods to use in the event of a hazardous materials fire.
In the Otsu-4 exam, questions such as "which extinguishing method to choose," "which extinguishing agent is suitable," and "whether the hazardous material can be extinguished with water" are frequently asked.
Make sure to understand these along with the properties of the hazardous materials.
The Three Principles of Fire Extinguishment
There are broadly three ways to extinguish a fire.
Removal Extinguishment
This is a method of removing the burning combustible material so that it can no longer continue to burn.
For example, moving burning wood away from the source of the fire or stopping the supply of combustible material falls under this category.
Smothering Extinguishment
This is a method of cutting off the oxygen necessary for combustion.
You can cut off the air by covering the liquid surface with foam extinguishing agent or by covering the source of the fire with sand or a blanket.
This is a very important extinguishing method for fires involving liquid hazardous materials.
Cooling Extinguishment
This is a method of using water or other substances to remove heat and lower the combustion temperature below the ignition point.
While this is the most basic extinguishing method for general fires, caution is required for Class 4 hazardous materials.
Fire Extinguishing Methods for Class 4 Hazardous Materials
Class 4 hazardous materials are flammable liquids.
Therefore, extinguishing methods that cause the burning liquid to scatter are not suitable.
Especially with hazardous materials that do not dissolve in water, such as gasoline or kerosene, spraying water with force may cause the liquid to spread, potentially causing the fire to expand instead.
For such fires, foam extinguishing agents that can cover the liquid surface to block oxygen, or powder extinguishing agents that suppress combustion reactions, are suitable.
Characteristics of Major Extinguishing Agents
In the exam, it is important to understand the characteristics of each extinguishing agent.
Water
It has an excellent cooling effect.
However, for hazardous materials lighter than water, such as gasoline or kerosene, the liquid floats on the water surface and continues to burn, so it is not suitable for extinguishing.
On the other hand, for water-soluble hazardous materials, dilution with water can sometimes be effective.
Foam Extinguishing Agent
It covers the liquid surface with foam, cutting off the supply of oxygen.
Furthermore, there is also a cooling effect from the moisture contained in the foam.
It is a representative extinguishing agent for Class 4 hazardous material fires.
Powder Extinguishing Agent
It extinguishes fires by suppressing the chain reaction of combustion.
It has a fast extinguishing speed and is used in many hazardous material facilities.
It is also widely adopted at gas stations and similar locations.
Carbon Dioxide Extinguishing Agent
It extinguishes fires by lowering the oxygen concentration.
Since it leaves no residue from the agent, it is also used for fires in electrical equipment and the like.
Points Often Mistaken in the Exam
In this field, the following types of questions are frequently asked.
Pouring a large amount of water onto a gasoline fire.
Foam extinguishing agents extinguish fires through a smothering effect.
Dry chemical extinguishing agents inhibit the chain reaction of combustion.
Carbon dioxide extinguishing agents can also be used for electrical fires.
For example, if there is an option stating "Water is most suitable for gasoline fires," it is incorrect.
Since gasoline floats on water, pouring water on it carries the risk of spreading the fire.
Such trick questions appear almost every year.
Key points to remember for the exam
The important points for this session are as follows:
The three principles of fire extinguishing are "removal, smothering, and cooling."
Foam extinguishing agents are suitable for liquid fires.
Dry chemical extinguishing agents inhibit the chain reaction of combustion.
Pouring a large amount of water is not suitable for gasoline fires.
Carbon dioxide extinguishing agents can also be used for electrical equipment.
Conclusion
In the event of a hazardous material fire, choosing the wrong extinguishing method in an attempt to put out the fire can actually cause the fire to spread.
In the Otsu-4 exam, questions are asked by linking the properties of each hazardous material with the characteristics of the extinguishing agents.
Instead of memorizing fire extinguishing methods in isolation, try to learn them as a set: "which extinguishing agent to use for which hazardous material."
Next time, we will review everything we have learned so far and organize the points that appear most frequently in the Otsu-4 exam.