What is fire extinguishing agent?
In the past, water was the main tool for human beings to put out fires. With the development of science and technology, humans have invented different forms of fire extinguishing agents, which have greatly improved the fire extinguishing efficiency of water, or used them in fire scenes where water cannot be directly extinguished, expanding the scope of fire extinguishing and protecting us from various fire hazards. Fire extinguishing agents can be roughly divided into water-based fire extinguishing agents, foam fire extinguishing agents, dry powder fire extinguishing agents and gas fire extinguishing agents according to their material form. Different types of fire extinguishing agents have different physical characteristics, different fire extinguishing mechanisms, and different types of fires. When we face a fire, choosing the right fire extinguishing agent and fire extinguishing equipment can achieve twice the result with half the effort.
Type of fire extinguishing agent, What fire scenarios can it cope with?
The most common fire extinguishing agent in life is water-based fire extinguishing agent. As the name suggests, it is a liquid fire extinguishing agent mixed with water and other chemical components. After being sprayed, the water-based fire extinguishing agent becomes a mist, which quickly evaporates the heat of the fire and reduces the temperature. The surfactant contained in it quickly forms a layer of water film on the surface of the combustible material, which has the dual functions of cooling and isolating oxygen, and participates in fire extinguishing at the same time, thereby achieving the purpose of rapid fire extinguishing.
When common solid combustibles such as coal, wood, cotton, linen, paper, plastic, rubber, etc. catch fire, water-based fire extinguishing agents can be used to put out the fire. Wood fire is a common fire scene in life. The following experiment uses a water-based fire extinguishing agent to put out a woodpile fire. It can be seen that after the fire extinguishing agent is sprayed into the woodpile, the flame is quickly extinguished.
Foam fire extinguishing agent
Foam fire extinguishing agent is an effective fire extinguishing agent for extinguishing flammable liquids. Foam fire extinguishing agent is miscible with water and produces foam for extinguishing fire through mechanical action or chemical reaction. It produces foam floating on the upper layer of flammable liquid, blocking the contact between liquid and air and cooling the burning liquid surface.
Foam fire extinguishing agents are commonly used to extinguish fires of liquids such as gasoline, kerosene, diesel, crude oil, methanol, ethanol, asphalt, paraffin, etc. In fires involving the petrochemical industry, a large amount of foam fire extinguishing agents are often required for fire fighting. The following experiment uses foam fire extinguishing agents to extinguish gasoline fires. It can be seen that after the foam is sprayed into the oil pan, the flame is gradually suppressed.
Dry powder fire extinguishing agent is made of fine particles made by mixing fire extinguishing base material with appropriate amount of lubricant and moisture-proof agent, and carbon dioxide is often used as the spray power. The fire extinguishing components in dry powder fire extinguishing agent can absorb free radicals in the combustion reaction and inhibit the chain reaction of combustion.
When some combustible metals such as magnesium, sodium, potassium, etc. catch fire, they react violently with water due to their active chemical properties. Therefore, dry powder fire extinguishers are often used to put out metal fires. The following experiment shows the use of dry powder fire extinguishers to put out the fire after magnesium metal catches fire. The magnesium metal catches fire quickly when it encounters fire, and the fire gradually decreases under the continuous spraying of dry powder fire extinguishers.
Gas fire extinguishing agent
Gaseous fire extinguishing agents are generally a mixture of inert gases such as carbon dioxide and nitrogen and halogenated alkanes such as heptafluoropropane and hexafluoropropane. When extinguishing a fire, the gaseous fire extinguishing agent quickly fills the fire space, effectively reducing the oxygen concentration in the space, thereby achieving the fire extinguishing effect.
Its biggest feature is that it will not cause pollution after extinguishing the fire, so it is often used to protect scenes such as libraries, archives, computer rooms, banks, etc. that store precision instruments or live equipment. The following experiment mainly simulates the use of heptafluoropropane gas fire extinguishing agent to extinguish a fire in a distribution cabinet. The automatic fire extinguishing equipment is triggered shortly after the oil pan in the distribution cabinet is ignited. The heptafluoropropane gas it sprays is mainly used for chemical fire extinguishing to achieve rapid and clean fire extinguishing. The fire is rapidly weakened, and the distribution cabinet after the fire is extinguished is almost not polluted by the fire extinguishing agent again.
