Fire safety knowledge article

First, the basic principles of fire fighting

According to several basic conditions necessary for combustion, fire extinguishing is the process of destroying combustion conditions and terminating combustion reaction. Its basic principle can be summarized as the following four aspects: cooling, suffocation, isolation and chemical inhibition.

1. cooling fire extinguishing: for general combustible substances, one of the conditions for continuous combustion is to reach their respective ignition temperatures under the action of flame or heat. Therefore, for the general combustible fire, when the combustible is cooled below its ignition point or flash point, the combustion reaction will stop. The fire extinguishing mechanism of water is mainly cooling.

2. Asphyxiation and fire extinguishing: The combustion of various combustible materials must be carried out above its minimum oxygen concentration, otherwise the combustion cannot continue. Therefore, the fire can be extinguished by reducing the oxygen concentration around the combustion products. The common fire extinguishing mechanism of carbon dioxide, nitrogen and steam is mainly suffocation.

3. Isolation and fire extinguishing: the combustible substance is isolated from the fire source or oxygen, and the combustion reaction will automatically stop. In case of fire, close the relevant valves and cut off the passage of combustible gas and liquid to the fire area; Opening the relevant valves to lead the liquid combustible in the container that has been burned or threatened by fire to a safe area through pipelines are all measures to isolate and extinguish the fire.

4. Chemical suppression fire extinguishing: that is, the fire extinguishing agent reacts with the intermediate free radicals in the chain reaction, thus interrupting the chain reaction of combustion and making the combustion unsustainable. The main fire extinguishing mechanism of commonly used dry powder fire extinguishing agents and halon fire extinguishing agents is chemical inhibition.

Second, several commonly used fire extinguishing agents and extinguishers

(A) several commonly used fire extinguishing agents

1. Water is the most widely distributed and cheapest fire extinguishing agent in nature. Because of its high specific heat (4. 186J/g℃) and latent heat (2260J/g), the cooling effect in fire extinguishing is very obvious, and its fire extinguishing mechanism mainly depends on cooling and suffocation. The main disadvantages of water extinguishing agent are water damage and pollution, so it can't be used to put out open flames.

2. Foam fire extinguishing agent: it is a kind of fire extinguishing agent which is miscible with water and produces foam through mechanical or chemical reaction. Generally, it consists of chemical substances, hydrolyzed protein or aqueous solutions of surfactants and other additives. There are usually chemical foam extinguishing agents, mechanical foam extinguishing agents and detergent foam extinguishing agents. The fire extinguishing mechanism of foam extinguishing agent is mainly cooling and suffocation, that is, a continuous foam layer is formed on the surface of the combustion object, the surface of the combustion object is cooled by the foam itself and the separated mixed liquid, and the combustion object is isolated from oxygen through the covering effect of the foam layer, thus extinguishing the fire. The main disadvantages of foam extinguishing agent are water damage and pollution, so it can't be used to put out open flames.

At present, the foam used in fire extinguishing system is mainly air-mechanical foam. According to the foaming multiple, it can be divided into three types: the foaming multiple below 20 times is called low-multiple foam; Between 2 1-200 times, it is called medium multiple foam; The foam with the ratio of 20 1- 1000 is called high multiple foam.

3. Dry powder fire extinguishing agent: it is a dry and flowable fine powder used for fire extinguishing, which consists of inorganic salt with fire extinguishing function and a small amount of additives. It is dried, crushed and mixed into fine solid powder. Mainly chemical inhibition and suffocation. In addition to the special dry powder extinguishing agent for metal fire, the commonly used dry powder extinguishing agents are generally divided into BC dry powder extinguishing agent and ABC dry powder extinguishing agent, such as sodium bicarbonate dry powder, modified sodium salt dry powder, ammonium dihydrogen phosphate dry powder, diammonium hydrogen phosphate dry powder, phosphoric acid dry powder and so on.

Dry powder fire extinguishing agent is mainly used to extinguish the fire through physical and chemical actions when the powder mist sprayed by pressurized gas contacts and mixes with the flame. First, the volatile decomposition of inorganic salts in dry powder and the free radicals or active free radicals produced by combustion substances have chemical inhibition and negative chemical catalysis, which interrupts the chain reaction of combustion and puts out the fire; Second, the powder of dry powder falls on the surface of combustible materials, causing chemical reaction, forming a covering layer under the action of high temperature, isolating oxygen and suffocating the fire. The main disadvantage of dry powder extinguishing agent is that it is easy to pollute the fire of precision instruments.

4. Carbon dioxide is a kind of gas fire extinguishing agent, which widely exists in nature and is cheap and easy to obtain. Its fire extinguishing mainly depends on suffocation and local cooling. The main disadvantage is that the fire extinguishing concentration needs to be high, which will cause suffocation and poisoning.

5. The fire extinguishing mechanism of haloalkane extinguishing agent is that when haloalkane is in contact with high temperature surface or flame, the active free radicals generated by decomposition will capture and consume a large number of free radicals generated in the chain reaction of combustion through the negative chemical catalysis and chemical purification of halogen hydride such as bromine and fluorine, thus destroying and inhibiting the chain reaction of combustion and quickly extinguishing the flame; Is to use chemical suppression to put out the fire. In addition, there are some oxygen dilution and cooling effects. The main disadvantage of haloalkane fire extinguishing agent is that it destroys the ozone layer. At present, there are two commonly used halon extinguishing agents:121kloc-0/and 130 1. 12 1 1 the molecular formula of the fire extinguishing agent is CF2ClBr, which is the most widely used halon fire extinguishing agent in China at present. 12 1 1 fire extinguishing agent is a liquefied gas with low boiling point, which has the advantages of high fire extinguishing efficiency, low toxicity, low corrosiveness, no deterioration after long-term storage, no trace after fire extinguishing, no pollution to protected objects and good electrical insulation performance. However, its chemical stability is good, the atmospheric ozone layer is seriously damaged, and advanced countries in the world have begun to eliminate it. China will also be eliminated after 20 10. 130 1 fire extinguishing agent has low toxicity, and it is one of halogenated alkyl fire extinguishing agents. It can be used in manned state, but the stability of 130 1 fire extinguishing agent is better than that of121kloc-0/fire extinguishing agent, which damages the ozone layer in the atmosphere.

(2) Brief introduction of several common fire extinguishers

The fire extinguisher consists of steel cylinders, nozzles, etc. It sprays the filled extinguishing agent with the help of driving pressure to achieve the purpose of fire extinguishing. It is an important fire-fighting equipment to put out the initial fire. Fire extinguishers can be divided into foam, dry powder, haloalkane, carbon dioxide, acid and alkali, clear water, etc.

1. foam extinguisher: refers to the foam extinguishing agent installed in the fire extinguisher, which can be divided into chemical foam extinguisher and air foam extinguisher.

Chemical foam extinguisher contains two chemicals: aluminum sulfate (acidic) and sodium bicarbonate (alkaline). When in use, the mixing of the two solutions causes a chemical reaction to produce foam, which is sprayed out under pressure to extinguish the fire. Air foam extinguisher filled with air foam fire extinguishing agent has excellent performance, long shelf life, high fire extinguishing efficiency and convenient use. It is an updated product of Chemical foam extinguisher. It can be filled with protein foam, fluorine-containing protein foam, polymer foam, light water (water film forming) foam and anti-soluble foam according to different needs.

The scope of application of foam extinguisher is Class B and Class A fires; Not applicable to open flames and C and D fires. Anti-solvent foam extinguisher can also put out water-soluble flammable and combustible liquid fires.

How to use the chemical foam extinguisher: The lifting ring on the upper part of the portable gas cylinder is close to the fire, and when it is about10m away from the fire point, the gas cylinder is turned over. Hold the lifting ring with one hand and the bottom ring of the cylinder with the other hand, and aim the jet at the burning object. When extinguishing the fire of flammable liquid, if it is already flowing and burning, spray foam from far and near, so that the foam completely covers the surface of the burning liquid; If burning in a container, the foam should be shot at the inner wall of the container, so that the foam can flow along the inner wall of the container and gradually cover the fire surface. It is strictly forbidden to spray directly on the liquid surface, so as to avoid the burning liquid rushing out of the container due to the impact of the jet and expanding the combustion range. When putting out a solid fire, the jet should be aimed at the place where the burning is the fiercest. During use, the fire extinguisher should always be in an inverted state, otherwise the spraying will be interrupted.

Maintenance requirements of chemical foam extinguisher:

(1) Store in a cool, dry, ventilated and convenient place. Don't be close to high temperature or sun exposure to prevent decomposition of sodium bicarbonate, prevent freezing in winter, and regularly check whether the nozzle is blocked and keep it unobstructed.

(2) Check regularly whether the sodium bicarbonate solution is invalid every year. The inspection method is to take out three parts of sodium bicarbonate solution from the steel cylinder, one part of aluminum sulfate solution from the bottle liner, and quickly put the two solutions into a measuring cup to see if the foam generated is more than six times the volume of the four parts. If it is less than 6 times, replace the extinguishing agent.

(3) If the extinguishing agent is replaced every time or the service life has exceeded two years, the water pressure test shall be conducted every year, and the test pressure shall be 0.5 times of the test pressure of 65438+ fire extinguisher. Only after passing the test can it be used, and the date of pressure test should be marked on the fire extinguisher.

How to use the air foam extinguisher: Lift the fire extinguisher about 6 meters away from the fire, pull out the safety pin, hold the opening knob in one hand and the spray gun in the other, squeeze the opening knob hard, open the seal or puncture the sealing plate of the gas cylinder, and air foam can be sprayed from the spray gun. The fire extinguishing method is the same as chemical foam extinguisher. However, unlike chemical foam extinguisher, when air foam extinguisher is used, the fire extinguisher should be in an upright state and cannot be used upside down or horizontally, otherwise the injection will be interrupted; Do not loosen the opening knob, otherwise the injection will be interrupted.

Maintenance of Air foam extinguisher

(1) The fire extinguisher should be placed in a cool, dry, ventilated and accessible place. The ambient temperature is 4~40 degrees, so pay attention to antifreeze in winter.

(2) Regularly check whether the nozzle is blocked and keep it unobstructed. Check whether the fire extinguisher has working pressure every six months. For the pressure storage air foam extinguisher, just check the pressure indicator, and if the pointer points to the red area, repair it in time; For air foam extinguisher with air bottle, it is necessary to open the cover to check the carbon dioxide cylinder, and check whether the weight is consistent with the weight on the cylinder. If the total weight of the cylinder is less than 25g, it should be inspected and repaired.

(3) Every time the fire extinguishing agent is replaced or three years after leaving the factory, the fire extinguisher should be tested for hydraulic strength, and it can only be used after the hydraulic strength is qualified.

(4) Fire extinguishers should be inspected by trained professionals and maintained by professional units with maintenance licenses.

2. Carbon dioxide fire extinguisher: The carbon dioxide fire extinguisher uses the vapor pressure of liquid carbon dioxide contained in it to spray carbon dioxide to extinguish the fire. Because carbon dioxide fire extinguishing agent has the characteristics of no trace and certain electrical insulation performance, it is more suitable for extinguishing the initial fires in places such as live appliances, expensive equipment, books and materials, instruments and meters below 600 volts, as well as the fires of general flammable liquids. That is, its application scope is Class A and Class B fires and low-voltage live fire.

When using carbon dioxide fire extinguisher to put out the fire, lift or carry the fire extinguisher to the fire site. When it is about 5 meters away from the combustible materials, put down the fire extinguisher, pull out the safety pin, hold the handle at the root of the horn with one hand, and hold the pressure handle of the switch valve with the other. For carbon dioxide fire extinguishers without water hose, pull the horn up 70-90 degrees. When using, do not directly grasp the outer wall of the horn or the metal connecting pipe with your hands to prevent frostbite. When extinguishing the fire, when the combustible liquid is burning in a flowing state, the user should spray the jet of carbon dioxide extinguishing agent from the near and far flame; If flammable liquid burns in the container, the user should raise the horn and spray it into the burning container from the upper part of one side of the container, but the carbon dioxide jet can not directly impact the surface of the flammable liquid, so as to prevent the flammable liquid from rushing out of the container, expanding the fire and causing fire extinguishing difficulties.

Cart-type carbon dioxide fire extinguishers are generally operated by two people. When in use, the fire extinguisher is pushed or pulled to the burning place by two people together, and stops at a distance of about 10 meter from the burning object. One person quickly takes off the horn, unfolds the water hose, holds the handle at the root of the horn, and the other person quickly turns the handwheel clockwise to the maximum position. The fire extinguishing method is the same as the portable method.

When using a carbon dioxide fire extinguisher, if it is used outdoors, it should be sprayed in the upwind direction; if it is used indoors in a narrow space, the operator should leave quickly after extinguishing the fire to prevent suffocation.

Maintenance of carbon dioxide fire extinguisher;

(1) The fire extinguisher should be stored in a cool, dry and ventilated place, not close to the fire source, and the ambient temperature should be between -5+45 degrees.

(2) The weight of the fire extinguisher should be checked once every six months and checked by weighing method. Compare the weighed weight with the total weight of the stamped steel seal at the bottom of the fire extinguisher cylinder. If it is less than 50g shown in the steel seal, it should be sent to the maintenance unit for maintenance.

(3) After each use or every five years, it should be sent to the maintenance unit for hydrostatic test. The hydrostatic test pressure should be the same as the value printed on the bottom of the cylinder. At the same time, the residual deformation rate of the cylinder should be measured. Only cylinders that have passed the water pressure test and the residual deformation rate is less than 6 can continue to be used.

3. Halon fire extinguishers: All fire extinguishers equipped with halon fire extinguishing agent are collectively called halon fire extinguishers. Commonly used are 12 1 1 and 130 1 fire extinguishers.

12 1 1 The fire extinguisher ejects by nitrogen pressure in the steel cylinder 12 1 1 extinguishing agent. Because 12 1 1 fire extinguishing agent is chemically inhibited, it has the advantages of high fire extinguishing efficiency, no pollution and insulation, and can be applied to all fires except metal fires, especially to the initial fires of precision instruments, computers, precious cultural relics and precious materials warehouses. 1

When using 12 1 1 fire extinguisher, it should be carried to the fire site by hand or shoulder. Put down the fire extinguisher about 5 meters away from the combustible, first pull out the safety pin, hold the opening knob with one hand and the nozzle at the front end of the spray hose with the other. If the fire extinguisher has no spray hose, hold the opening knob with one hand and the bottom ring of the fire extinguisher with the other. Firstly, aim the nozzle at the burning place, and open the handle hard to make the fire extinguisher spray. When the rescued combustible liquid flows and burns, the user should aim at the ignition point from near to far and from left to right, and advance quickly until the flame is completely extinguished. If combustible liquid burns in the container, the quasi-flame should be shaken and sprayed from left to right. When the flame is driven out of the container, the jet will follow the flame until it is completely extinguished. However, it should be noted that the jet cannot be directly sprayed on the surface of the burning liquid, so as to prevent the momentum of the extinguishing agent from flushing the flammable liquid out of the container, which will expand the fire and bring difficulties to the fire extinguishing. If the initial surface fire of combustible solid materials is put out, the jet should be aimed at the place where the burning is the fiercest. After the flame is extinguished, measures should be taken in time to prevent reignition. 12 1 1 When using the fire extinguisher, it should not be inverted or placed horizontally, otherwise the fire extinguishing agent will not be sprayed out. In addition, when used outdoors, it should be sprayed in the upwind direction. When putting out the fire in a narrow indoor space, the operator should spread it quickly after putting out the fire, because the extinguishing agent 12 1 1 is also toxic to prevent harm to human body.

12 1 1 Maintenance of fire extinguishers:

(1) should be stored in a ventilated, dry, cool and convenient place, and the ambient temperature should be between-10-+45 degrees.

(2) Don't store it near heating equipment, and don't put it in a place with direct sunlight and strong corrosiveness.

(3) Check the internal pressure display on the fire extinguisher about once every six months. If it is found that the pointer has dropped to the red area, it should be sent to the maintenance department for repair in time.

(4) After each use, whether there is surplus or not, it should be sent to the maintenance department for refilling. Before each refilling or more than three years after leaving the factory, the water pressure test should be carried out. The test pressure is the same as the value marked on the label, and can only be used after passing the test.

(5) If there is no internal pressure indicator on the fire extinguisher, it can be weighed. When the weighing weight is less than 90% of the weight indicated on the label, it should be sent to the maintenance department for maintenance. It is best to buy a 12 1 1 fire extinguisher with an internal pressure indicator.

130 1 CF2Br fire extinguisher: 13065438+

130 1 Use and maintenance of fire extinguishers

130 1 The use method and application scope of the fire extinguisher are the same as those of 12 1 kloc-0/fire extinguisher, but the fire extinguishing ability of 130 1 fire extinguisher is not as good as that of/kloc-0 when it is used outdoors in windy conditions.

The maintenance method is the same as 12 1 1 fire extinguisher. Please refer to 12 1 1 fire extinguisher.

4. Dry powder fire extinguisher: The dry powder fire extinguisher is powered by liquid carbon dioxide or nitrogen, and the dry powder extinguishing agent in the extinguisher is sprayed to extinguish the fire. It is suitable for extinguishing initial fires of petroleum and its products, flammable liquids, flammable gases and flammable solid substances. Because dry powder has more than 50 thousand volts of electrical insulation, it can also put out the fire of live equipment. This kind of fire extinguisher is widely used in factories, mines, oil depots and traffic places.

Application scope of dry powder fire extinguisher: Sodium bicarbonate dry powder fire extinguisher is suitable for the initial fire of flammable, combustible liquid, gas and charged equipment; Ammonium phosphate dry powder fire extinguisher can be used not only for the above kinds of fires, but also for the initial fire of solid substances. But they can't put out the burning flame of light metal.

When using dry powder fire extinguisher to put out the fire, you can quickly walk to the fire with your hands or shoulders, and put down the fire extinguisher about 5 meters away from the burning materials. If you are outdoors, you should choose to spray against the wind. If the dry powder fire extinguisher used is an external gas cylinder, the operator should hold the spray gun tightly with one hand and lift the opening bail on the gas cylinder with the other hand. If the opening of the gas cylinder is pushed by hand, unscrew it in the opposite direction and turn it to the highest position, then lift the fire extinguisher. When the dry powder is ejected, it is quickly aimed at the root of the flame. If the dry powder fire extinguisher used is a built-in gas cylinder or pressure storage type, the operator should first remove the safety pin on the opening handle, then hold the nozzle root at the front end of the spray hose, press the opening handle with the other hand, and open the fire extinguisher to spray and extinguish the fire. When using a fire extinguisher with spray hose or accumulator fire extinguisher, always hold down the handle with one hand and never let go, otherwise the spray will be interrupted.

When using dry powder fire extinguisher to put out flammable and combustible liquid fires, shoot at the root of the quasi-flame. If the extinguished liquid fire is burning, aim at the root of the flame from near to far and spray the flame from left to right until the flame is completely extinguished. If combustible liquid burns in the container, the user should shake the root of quasi-flame left and right to make the sprayed dry powder flow cover the whole opening surface of the container; When the flame is driven out of the container, the user should continue to spray until the flame is completely extinguished. When extinguishing the flammable liquid fire in the container, it should be noted that the nozzle should not be directly aimed at the liquid surface to prevent the impact of the jet from spraying flammable liquid, which will expand the fire and bring difficulties to the fire extinguishing. If the combustible liquid burns in a metal container for a long time, the wall temperature of the container is higher than the self-ignition point of the extinguished combustible liquid, which is easy to cause re-ignition after fire extinguishing. It can be used with foam extinguisher to achieve better fire extinguishing effect.

Maintenance of dry powder fire extinguisher

(1) The fire extinguisher should be placed in a ventilated, dry, cool and convenient place with the ambient temperature of -5-+45 degrees.

(2) The fire extinguisher should avoid high temperature, humidity and severe corrosion to prevent the dry powder extinguishing agent from caking and decomposing.

(3) Check whether the dry powder is caked and whether the carbon dioxide gas in the gas cylinder leaks every six months. Check the carbon dioxide cylinder. Remove the gas cylinder and weigh it. Whether the weighing value is the same as the value marked on the steel seal on the gas cylinder. If it is less than 7 grams of the marked value, it should be sent to the maintenance department for repair. If it is a pressure storage type, check its internal pressure display table to see if the pointer is in the green area. If the pointer is already in the red area, it means that the internal pressure has leaked and cannot be used, and it should be sent to the maintenance department for repair.

(4) Once the fire extinguisher is turned on, it must be refilled. When refilling, the type of dry powder fire extinguishing agent shall not be changed, that is, ammonium phosphate dry powder fire extinguishing agent shall not be used instead of dry powder sodium bicarbonate fire extinguisher.

(5) Before each replenishment or three years after the fire extinguisher leaves the factory, a water pressure test should be conducted. During the water pressure test, the fire extinguisher cylinder and gas cylinder should be carried out separately. The hydrostatic test pressure shall be the same as that shown on the label or steel seal of the fire extinguisher. It can only be refilled after passing the water pressure test.

(6) Maintenance must be carried out by trained personnel, and maintenance and supplement should be sent to professional maintenance units.