【Q&A】May 26, 2017

Principle: Compressed carbon dioxide is used to blow out the dry powder, thereby interrupting the combustion reaction and isolating oxygen to extinguish the fire

Dry powder and inert gases prevent oxygen from reaching the fire, preventing it from continuing to burn and thus extinguishing the fire

A fire extinguishing agent is a dry, flowable fine powder used for extinguishing fires; it is composed of inorganic salts with fire-extinguishing properties along with small amounts of additives, all combined into a fine solid powder through drying, crushing, and mixing. It is a fire extinguishing agent widely used in firefighting, and it is primarily used in fire extinguishers. Apart from the specialized dry chemical extinguishing agents used to fight metal fires, dry powder extinguishing agents are generally divided into two main categories: BC dry powder extinguishing agents and ABC dry powder extinguishing agents. Dry powder fire extinguishants extinguish fires through physical and chemical reactions that occur when the powder mist, ejected under the action of pressurized gas, comes into contact with and mixes with the flame. In addition, it also has a role in diluting oxygen and cooling. 　　The most common way to operate a dry powder fire extinguisher is by pressing the handle. After bringing the fire extinguisher to an appropriate distance from the source of fire, invert it several times up and down to loosen the dry powder inside the cylinder. Then aim the nozzle at the area where the fire is most intense, remove the safety pin, press the handle, and the extinguishing agent will be discharged to put out the fire. To activate the dry powder fire extinguisher, hold its middle part with the left hand and aim the nozzle at the base of the flame. With the right hand, remove the safety latch and turn the activation knob to open the gas cylinder; after a delay of 1–4 seconds, the dry powder will be discharged to extinguish the fire.

First, it relies on the volatile decomposition products of the inorganic salts in the dry powder, which exert a chemical inhibitory and negative catalytic effect on the free radicals or reactive groups generated by the fuel during combustion, thereby interrupting the chain reaction of combustion and extinguishing the fire； Secondly, the powder in the dry chemical extinguisher falls onto the surface of the combustible material, where it undergoes a chemical reaction; under high temperatures, this forms a glass-like coating that prevents oxygen from reaching the fuel, thereby suppressing the fire. The most common way to activate a dry chemical extinguisher is by pressing the handle. After bringing the fire extinguisher to an appropriate distance from the source of fire, invert it several times up and down to loosen the dry powder inside the cylinder. Then aim the nozzle at the area where the fire is most intense, remove the safety pin, press the handle, and the extinguishing agent will be released to put out the fire. To activate a dry powder fire extinguisher, hold the middle part with the left hand and aim the nozzle at the base of the flame. With the right hand, remove the safety pin and turn the activation knob to open the gas cylinder; after a delay of 1–4 seconds, the dry powder will be ejected to extinguish the fire.

:Principle of fire extinguishing: Dry powder consists of fine solid particles, whose main component is sodium bicarbonate (or potassium bicarbonate). Under the pressure of carbon dioxide or nitrogen, it is sprayed in the form of a powder mist. In the burning area, the following reaction takes place: 2NaHCO3 → Na2CO3 + H2O + CO2↑ – Q (heat). During this reaction, a large amount of heat is absorbed, along with significant amounts of water vapor and carbon dioxide gas. The dry powder reacts with hydrocarbons to produce free OH and H radicals. The OH radicals absorb oxygen from the burning surface to form vapor, while the free hydrogen atoms capture oxygen atoms in the burning area to form OH radicals. This chain reaction occurs very rapidly, reducing the oxygen content in the burning area and thus extinguishing the fire. Applications: Suitable for extinguishing fires involving petroleum products, organic solvents, and electrical equipment. Usage: To use it, remove the safety pin, hold the nozzle against the flame with your left hand, and lift the trigger with your right hand to release the dry powder.

Principle: A dry powder fire extinguisher uses carbon dioxide or nitrogen as a propellant to spray the dry powder inside the cylinder to extinguish the fire. Dry powder is a dry, flowable fine solid powder composed of a fire-extinguishing base material along with additives such as moisture inhibitors, flow promoters, and anti-caking agents. Usage: When extinguishing a fire, stand 5 meters away from the source of the fire, hold the nozzle in one hand and the opening ring in the other, position yourself upwind, and spray while aiming at the base of the flame. If there is a safety plug, it should be removed before spraying, and then spraying can proceed. The process must not be interrupted, otherwise the flame will reignite.

Dry powder fire extinguishers are filled with dry powder extinguishing agent. Dry powder extinguishing agents are dry and flowable fine powders used for extinguishing fires; they consist of fine solid particles formed by drying, crushing, and mixing inorganic salts with fire-extinguishing properties along with small amounts of additives. It is a fire extinguishing agent widely used in firefighting, and it is primarily used in fire extinguishers. Apart from the specialized dry chemical extinguishing agents used to fight metal fires, dry powder extinguishing agents are generally divided into two main categories: Bc dry powder extinguishing agents and ABC dry powder extinguishing agents. Dry powder fire extinguishants extinguish fires through physical and chemical reactions that occur when the powder mist, ejected under the action of pressurized gas, comes into contact with and mixes with the flame. In addition, it also has a role in diluting oxygen and cooling. The most common way to operate a dry powder fire extinguisher is by pressing the handle. After bringing the fire extinguisher to an appropriate distance from the source of fire, invert it several times up and down to loosen the dry powder inside the cylinder. Then aim the nozzle at the area where the fire is most intense, remove the safety pin, press the handle, and the extinguishing agent will be discharged to put out the fire. To activate the dry powder fire extinguisher, hold its middle part with the left hand and aim the nozzle at the base of the flame. With the right hand, remove the safety latch and turn the activation knob to open the gas cylinder; after a delay of 1–4 seconds, the dry powder will be discharged to extinguish the fire.

How to use a dry powder fire extinguisher: When extinguishing a fire, stand 5 meters away from the burning area, hold the nozzle in one hand and the release ring in the other, position yourself upwind to spray, and aim at the base of the flame. If there is a safety pin, it should be removed before spraying, and then spraying should proceed. The process must not be interrupted, otherwise the flame will reignite.   Principle of dry powder fire extinguishers: Dry powder fire extinguishers use carbon dioxide or nitrogen as a propellant to spray the dry powder inside the container to extinguish fires. Dry powder is a dry, flowable fine solid powder composed of a fire-extinguishing base material along with additives such as moisture inhibitors, flow promoters, and anti-caking agents.  

Principle: Firstly, it relies on the volatile decomposition products of inorganic salts in the dry powder, which exert a chemical inhibitory and negative catalytic effect on the free radicals or reactive groups generated by the fuel during combustion, thereby interrupting the chain reaction of combustion and extinguishing the fire； Secondly, the powder falls on the surface of the combustible material, where it undergoes a chemical reaction; under high temperatures, this forms a glass-like coating that prevents oxygen from reaching the material, thereby extinguishing the fire through suffocation. In addition, there is also some dilution of oxygen and a cooling effect. Usage: The most common way to activate a dry powder fire extinguisher is by using the handle. After bringing the extinguisher to an appropriate distance from the source of fire, shake it up and down several times to loosen the dry powder inside the container. Then point the nozzle at the area where the fire is burning most intensely, remove the safety pin, and press the handle – the extinguishing agent will then be released to put out the fire. The rotation method can also be used. To activate the dry powder fire extinguisher, hold the middle part with the left hand and aim the nozzle at the base of the flame. With the right hand, remove the safety latch and turn the activation knob clockwise to open the gas cylinder; after a delay of 1–4 seconds, the dry powder will be discharged to extinguish the fire.