What properties of carbon dioxide are used in fire extinguishing?

Taking advantage of the fact that carbon dioxide is not combustible, it cannot support combustion, and at the same time, the density is higher than that of oxygen, which can isolate the action of oxygen.

Carbon dioxide properties.

1) Physical properties of carbon dioxide:

a.Carbon dioxide is a colorless, odorless gas that is soluble in water. In standard condition.

The density of carbon dioxide is, about twice the weight of air. Under pressurization and cooling, carbon dioxide is converted into a liquid. At lower temperatures, liquid carbon dioxide.

It can solidify into a white snow-like solid called "dry ice."

As shown in the figure below).Dry ice can be sublimated and converted directly from a solid to a gas carbon dioxide. - Dry ice.

b.Carbon dioxide is not combustible and does not support the combustion of general combustibles, so it can be used to extinguish fires. Carbon dioxide does not support animal respiration.

Usually the air contains very little carbon dioxide (, no harm to people, if more than 1% is harmful, it will make people uncomfortable, more than 10%, so that people do not wake up, respiratory arrest and death.

CO2 fire extinguisher.

Fire extinguishing principle: under normal temperature and pressure conditions, the state of carbon dioxide is the gas phase. When stored in sealed high-pressure cylinders, below the critical temperature.

It is the coexistence of gas and liquid. During the extinguishing process, when carbon dioxide is released from the storage cylinder, the pressure drops suddenly, causing the carbon dioxide to change from liquid to gaseous, diluting the oxygen content in the air. A decrease in oxygen content reduces the rate of heat generation during combustion, and combustion stops when the rate of heat generation decreases below the rate of heat loss.

When carbon dioxide is released, the temperature drops sharply due to the enthalpy drop, forming fine solid dry ice particles, which absorb the surrounding heat and sublimate, that is, it can produce the effect of cooling combustibles.

However, the fire extinguishing effect of carbon dioxide is mainly suffocation, and cooling plays a secondary role. Application place: It is suitable for places where there can be no stains after extinguishing the fire, according to the "Building Design Code".

and Code for Fire Protection of High-rise Civil Buildings

can be applied to computer rooms, data repositories, power distribution rooms, generator rooms, libraries, archives.

Installed in fire hazard places of production operations: such as oil immersion tanks, rolling mills, drying equipment, cooking stoves, painting production lines, pulverized coal silos, etc.

1. Carbon dioxide does not burn and does not support combustion.

2. The density of carbon dioxide is higher than that of oxygen, which plays the role of isolating oxygen.

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Carbon dioxide fire extinguishers are suitable for extinguishing books, archives, valuable equipment, precision instruments, electrical equipment and oil fires below 600 volts. It is suitable for fighting Class B fires (such as kerosene, diesel, **, methanol, ethanol, asphalt, paraffin, etc.) ), Class C fires (such as gas, natural gas, methane, ethane, propane, hydrogen, etc.) , and Class E fires (fires in which objects are burned with electricity). Carbon dioxide extinguishing agent is a fire extinguishing agent that has been used for more than 100 years. It is cheap, readily available and prepared, and relies primarily on asphyxiation and local cooling to extinguish fires.

Carbon dioxide fire extinguishers are suitable for fighting Class B fires (such as kerosene, diesel, **, methanol, ethanol, asphalt, paraffin, etc.); Suitable for fighting Class C fires (such as gas, natural gas, methane, ethane, propane, hydrogen, etc.); Extinguishing Class E fires (fires in which objects are charged and burned). In addition, it can also be used to extinguish books, archives, valuable equipment, precision instruments, electrical equipment below 600 volts and oil.

CO2 fire extinguisher.

It has excellent properties such as good fluidity, high injection rate, non-corrosive container and non-deterioration, and is used to extinguish the initial disaster of books, archives, valuable equipment, precision instruments, electrical equipment below 600 volts and oil. It is suitable for fighting Class B fires (such as kerosene, diesel, **, methanol, ethanol, asphalt, paraffin, etc.); Suitable for fighting Class C fires (such as gas, natural gas, methane, ethane, propane, hydrogen, etc.); Extinguishing Class E fires (fires in which objects are charged and burned).

Fire extinguishers "five families".

In everyone's impression, the appearance of fire extinguishers is red, but in recent years, there are many green bottle fire extinguishers on the market. Is there any difference? In this regard, the Nanjing fire department explained that the distinction of fire extinguishers is not based on the color of the bottle, but according to the filled fire extinguishing agent.

There are five most common types of fire extinguishers, which are water-based fire extinguishers, foam fire extinguishers, dry powder fire extinguishers, halide fire extinguishers, and carbon dioxide fire extinguishers.

For different types of fires, fire extinguishers can not be big or small, but choose different types of fire extinguishers according to the type of fire in the place. If you choose an inappropriate fire extinguisher, not only can you not extinguish the fire, but also may cause a reverse chemical reaction, and even cause a first-class injury accident.

The most common things we come into contact with in our citizens' lives are water-based fire extinguishers and dry powder fire extinguishers. The former is suitable for extinguishing the initial disaster of flammable solids or non-water-soluble liquids. The latter has a wide range of applications and is suitable for extinguishing initial disasters such as oil, combustible gas, and electrical equipment.

1. Non-flammable, non-combustible.

2. Easy to compress (in the storage tank, it is actually solid carbon dioxide, that is, dry ice).

3. The density of Zhaoye is greater than that of air, so that spraying on the flame can cover the flame like a pot lid, so that the flame can be suffocated and extinguished.

4. At low temperature, a large amount of heat is absorbed during the vaporization of dry ice, so that the temperature of the ejected CO2 gas is very low, and the ridge can be hidden to absorb the heat of the flame.

5. Carbon dioxide is not conductive, so it can be used to extinguish the fire of the electric family let without fear of leakage.

6. After the fire is extinguished, there is no residue of fire extinguishing agent, and the damage to the first object is minimal. This is the biggest advantage of carbon dioxide fire extinguishers over water, foam, and dry chemical fire extinguishers, so it is especially suitable for extinguishing fires such as precision instruments and precious documents.

Answer]: a, b

The extinguishing effect of carbon dioxide is mainly suffocation, followed by cooling. The wetting effect in option C and the emulsification effect in option D are mainly for the water medium, and the isolation effect in option E is not accurate enough, and the carbon dioxide in Xinghuai is only diluted and suffocated rather than disturbed and isolated.

First of all, there are three necessary conditions for the combustion of objects: combustibles, oxygen, and the necessary temperature, and removing one of the three can achieve the effect of extinguishing the fire, and carbon dioxide can be used to extinguish the fire because:

1. Carbon dioxide can neither burn nuclear travel nor support combustion in the air;

2. The density of carbon dioxide is larger than that of air, which can cover the surface of the combustion and play the role of isolating the air.