How to classify fire extinguishing levels of fire extinguishers

As fire emergency equipment, fire extinguishers are of various types and widely used. When choosing a fire extinguisher of appropriate type and specification, we should not only consider its fire extinguishing agent category, but also focus on its key performance indicator, the "fire extinguishing level". The fire extinguishing level reflects the ability of the fire extinguisher to actually control and extinguish the fire source, and is the core basis for evaluating its effectiveness and adaptation scenarios.

Definition of fire extinguishing level
The fire extinguishing level refers to the scale of the standard fire source that the fire extinguisher can extinguish under standard test conditions, which is used to measure its actual fire extinguishing effectiveness. The fire extinguishing level consists of letters and numbers, where the letters represent the fire category and the numbers represent the maximum standard fire source model that can be extinguished.
Common fire extinguishing level formats include:
Class A fire: for example, "3A", "5A", "8A";
Class B fire: for example, "21B", "55B", "89B";
Class C, D, and F fires: some countries do not use numbers to divide, but only use letters to indicate applicability.
Fire extinguishing level information is usually marked on the fire extinguisher label and instruction manual, which is a mandatory label content.

Classification standard of fire extinguishing level
Class A fire: refers to combustible solid materials, such as wood, paper, fabric, etc.
The number of Class A fire extinguishing level represents the fire extinguishing ability on the standard firewood pile model;
For example, "5A" means that the fire source of the wood pile model with a height of 1.5 meters and a width of 0.5 meters can be extinguished;
The layout, moisture content, and ignition method of the wood pile model are all subject to national standards.
Class B fire: refers to liquid or fusible solids, such as gasoline, alcohol, lubricating oil, paraffin, etc.
The number of Class B fire extinguishing level represents the fire extinguishing ability on the standard fuel liquid tray;
For example, "55B" means that the fire source of the fuel oil tray with a diameter of 55 cm can be extinguished;
In the fire extinguishing experiment, the flame must be extinguished within the specified time and re-ignition must be prevented.
Class C fire: gas fire, usually without a numerical level. Whether the fire extinguisher is suitable for Class C fire is determined by conductivity and the diffusion capacity of the fire extinguishing agent.
Class D fire: Metal burning fire, the level assessment is based on the actual test results, and there is no unified classification. It is usually marked separately as "applicable to magnesium, sodium, aluminum fires", etc.
Class F fire: Vegetable oil fire, mainly occurs in the kitchen. Some standard systems (such as EN 3) set the fire extinguishing level of Class F fire extinguishers, such as "25F".

Test method for fire extinguishing level
Class A fire extinguishing test:
Construct a standard firewood pile model;
Use a certain amount of fuel to assist ignition;
The fire extinguisher sprays the fire extinguishing agent within the specified time;
Observe whether the fire source is completely extinguished and prevented from re-igniting.
Class B fire extinguishing test:
Use a metal combustion tray to hold a specified amount of fuel;
Start extinguishing after ignition to a stable combustion state;
Judge whether the fire extinguisher extinguishes the fire within the specified time and the fuel does not re-ignite.
All tests must be carried out at room temperature and windless conditions, and the spraying distance, spraying time, residual amount of fire extinguishing agent, and operational stability are all used as evaluation factors.

Factors affecting the fire extinguishing level
Type of fire extinguishing agent:
Dry powder fire extinguishers usually have a higher class B fire extinguishing level;
Water-based fire extinguishers are more advantageous in class A fires;
Carbon dioxide fire extinguishers are suitable for class B and class C fires, but the fire extinguishing level is relatively limited.
Fire extinguisher capacity:
The amount of fire extinguishing agent directly affects the fire extinguishing level;
For the same type of fire extinguishing agent, 6kg fire extinguishers are usually higher than 3kg.
Spraying performance:
Spraying distance and spraying time determine the fire extinguishing range and continuous ability;
High-performance fire extinguishers are usually equipped with enhanced nozzles and stable compressed gas systems.
Manufacturing process:
High-standard fire extinguishers use pressure-resistant bottles and double-sealed designs;
Precise pressure control systems can improve fire extinguishing efficiency and spray consistency.

Practical application of fire extinguishing level in configuration
Fire extinguisher configuration standards are usually based on the matching of fire extinguishing level and risk level:
Ordinary offices and residences are equipped with 3A/21B and above fire extinguishers;
Shopping malls, warehouses, factories and other places with high fire loads are equipped with 5A/55B and above;
Oil depots and laboratories are equipped with high-efficiency fire extinguishers with fire extinguishing level ≥89B;
Special vehicles or electrical rooms give priority to fire extinguishers with Class C identification.
The design of building fire extinguisher configuration also needs to refer to the "Building Fire Extinguisher Configuration Design Code" (GB 50140) and the "General Technical Conditions for Portable Fire Extinguishers" (GB4351).