Heroic mother, please send a sorrow! We will study the fire technology carefully to ensure that our brothers go home safely!

First, the definition of fire smoke

As one of the important tactics in the fire extinguishing process, the purpose of the fire smoke exhaust is to discharge the combustion products produced by the building fire. In recent years, firefighters have continuously developed and refined the method of smoke emission from fire sites, and the efficiency of the discharge of combustion products within buildings has become higher and higher.

Exhaust from the fire can be defined in such a way that the heat inside the building and toxic fumes are systematically and harmoniously discharged and replaced with room temperature and fresh air.

In this definition, there are two words that must be grasped to understand what constitutes the best way to discharge smoke: systemic and collaborative.

"Systematic" means following or obeying a plan. Just as with all firefighting actions, effective smoke emission is not a random event. It is achieved through systematic and practical planning.

An effective exhaust should start with the established procedures and follow the plan. If done correctly, you can get the expected smoke exhaust effect.

"Synergistic" refers to acting together in a coordinated, seamless way. Exhaust smoke is as important as fire extinguishing. In order to obtain the best efficiency, exhaust smoke and skirts will be deflated. Rebel rabbits, halo swords, and bananas will be knocked on.蟮蟮跋欤?踔烈允О芨嬷铡?/span>

Cooperative smoke exhausting plays an important role in the entire fire extinguishing and rescue operation, but there are also great difficulties. It is an important issue that needs to be paid attention to in the study of fire extinguishing tactics in the process of fire extinguishing.

Second, what is an effective fire smoke exhaust

Regardless of the stage of the fire, it is beneficial to emit heat and toxic fumes. Not only does it help the safety evacuation of people in the fire, but the effective smoke can also be a fire field.

In the fire field, speed and efficiency are extremely important. This requires that the exhaust, rescue and fire fighting can all be completed as quickly as possible, and they can cooperate with each other.

When the fire commanders face the fire, they should not only consider extinguishing fires. Exhaust smoke is also one of the most important tasks to be considered and should be given priority.

This is because a suitable fire smoke exhaust can rapidly eliminate a large number of toxic gases and a lot of heat in the fire. It will have a positive impact on the safety of people, fire fighting and property protection.

Exhaust fumes should be coordinated with fire fighting, but the timing of smoke exhaust plays a crucial role in it.

Ideal timing: Exhaust smoke should be conducted before the firefighters extinguish the fire. Since the flue gas = combustibles, it is best to have substantial bring the water, just in case.

This is not to say that firefighters try to save people and extinguish fire while trying to smoke. On the contrary, exhaust smoke should be carried out before actions such as saving people and extinguishing fires take place.

Firefighters can quickly control the fire if they face a good environment in the fire scene, that is, the visibility of the fire field is good enough and the temperature is not high.

At the same time, in this kind of environment, firefighters can only observe the larger fire area through the naked eye, and can quickly transfer the trapped people exposed to toxic smoke.

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Time is an important factor. Only effective discharge of smoke as soon as possible can be used to obtain time for internal attack and extinguishing. If exhaust smoke is conducted too late, it will greatly affect its effectiveness.

In addition to time, there are other factors that need attention. The actual situation of smoke exhaust and fire is related to each other, and the relationship between the two must be balanced.

If you do not increase the visibility of your building after you have exhausted it, you must be clear about what limitations exist. No matter which smoke exhaust method is adopted, it must adapt to the fire in the fire field and the demand of the flue gas produced.

The fourth quarter , the role of fire smoke

The correct and effective smoke emission from the fire can help the firefighters to carry out firefighting and rescue operations to a large extent, and can enable the firefighters to enter an environment that could not have been operated.

However, at the same time, the operating requirements for the smoke from the fire are extremely strict. If you make mistakes, you may speed up the spread of the fire and quickly spread the fire to the entire building, resulting in major property damage and casualties.

Effective smoke extraction has the following advantages:

First, it is conducive to the survival and search and rescue of trapped persons

The building is full of toxic gases, which can reduce the amount of oxygen that can be inhaled. Visibility is reduced. One of the most important goals for firefighters to carry out smoke on the fire is to increase the chance of survival for the trapped.

In building fires, dangers such as burning and collapse continue to threaten trapped people, and the smoke in fire is the most harmful to those trapped.

According to the NFPA handbook, “Most of the deaths in building fires are related to smoke, which is usually caused by reduced oxygen in the blood and the replacement of oxygen in hemoglobin with carbon monoxide.” This is not smoke. The only effect on trapped people.

In the firefighting manual, it was also written: "The thick smoke layer will not only reduce the visibility but also have a strong stimulant effect on people's eyes. These two points will cause trapped people to have anxiety, panic and other emotions."

These factors make the trapped people panic and disorientate, greatly increasing the difficulty of escape.

A research institute in the United States conducted a related fire environment simulation study on a hotel. The main research object in this simulation scenario was a hotel room where furniture was placed.

Research shows that after the chair has changed from smoldering to flaming, the fire has developed rapidly and the fire has developed into a flash fire in about 8 minutes.

At the same time , a series of life-threatening conditions, such as an increase in temperature in the room, increased toxic gases such as CO and HCN, and reduced oxygen levels, will occur.

After the flashover occurred, the environment in the farther room deteriorated, and the experimental animals inside could not move within 2 minutes. After the flashover occurred, the suffocation death caused by CO occurred in about 11 minutes. People in more distant rooms will also be unable to move and die at the same time.

From the point of view of the development of the fire, the most important thing in controlling the fire is to grasp the eight minutes before the flash fire , because this is the best time for rescue.

During this period of time, the fire brigade must be alerted in a timely manner. The fire brigade should quickly rush to the scene and quickly spread the water. In addition, firefighters should enter the building to conduct investigations to find and rescue trapped people as soon as possible.

During the time that trapped people are waiting for rescue, they have been inhaling toxic substances, and the temperature of these toxic substances has been rising even to a deadly extent.

The deceased person caused by the fire has black carbon black in the respiratory tract and lungs, and the amount of CO contained in the blood reaches a lethal concentration.

The Canadian International Research Council report pointed out that trapped persons can only survive for a short period of time when the temperature of the inhaled air exceeds 149 °C .

If there is a high temperature of steam in the air, trapped people have no possibility of survival.

When the fire starts to develop from the initial stage, the temperature in the building will rise rapidly, and at this time, the possibility of survival will only increase as close to the floor as possible.

When the high temperature inside the building, inside will produce large amounts of water vapor to the water jet, which if trapped in a positive result in serious injury. If you do not pass the timely exhaust and remove a lot of heat inside the building, the trapped will not be able to survive.

Trapped people in the fire will also be directly affected by the high temperature of the flame. When the temperature of the fire exceeds 55 °C , the human skin will burn quickly in a short period of time.

Due to the effects of various aspects of the fire environment, trapped persons may experience increased shock, inhalation of excessive toxic gases and heat, and may experience shock, hyperthermia, and fatal heart disease.

The use of thermal imagers in firefighting forces is becoming more and more common. Even if the instrument can assist in locating trapped persons and speed up rescue operations, such instruments are only used to locate trapped persons.

If the interior of the building is full of smoke and there is not enough personal protective equipment, the chances of survival of the trapped are not as great.

For those trapped inside the building, exhaust smoke can improve their survival.

This is because the smoke can not only emit a large number of toxic gases, effectively reducing the temperature of the fire field, but also can greatly increase the visibility in the fire field, creating favorable conditions for the evacuation of people and the search and rescue of firefighters, thereby greatly improving the survival probability of the trapped.

Modern protective equipment allows firefighters to go deeper into the interior of a building than ever before. The smoke will reduce the efficiency of the rescue. Only the smoke exhaust can enable firefighters to observe with their eyes, except touching and listening.

Increased visibility can increase the speed of the rescue process and increase the survival rate of the trapped.

If the fire is full of smoke, the firefighters will not be able to see trapped persons. The best rescue time for those trapped will also be delayed. High-efficiency exhaust smoke will also allow firefighters to quickly evacuate after finding trapped persons.

On the other hand, being able to see the nearest safe exit is also the only way for trapped people to save themselves.

Second, protect firefighters

When the line of sight was blocked, most of the firefighters had to make advancement on the floor and could only touch any possible trapped person with their hands and feet.

The weakening of smoke by firemen is a huge threat. There are various “traps” hidden in the fires filled with fire smoke, including vertical shafts, open stairs, burnt floors, bare wires and other dangers.

A variety of news and industry magazines have reported that many firefighters could not find the right exit due to the smoke of fire after they entered the fire scene, which in turn led to death.

Sometimes, these dead people are only one step away from the safe exit at the time of death, but a lot of smoke makes them unable to find a way out.

In this case, it is advisable to exhaust the building quickly, and the smoke must be coordinated with internal attackers to prevent the fire from spreading to the location of the trapped person.

In areas where smoke is discharged, rescue workers can rescue trapped people more quickly, while also improving the safety of rescue operations and protecting the firefighters' own safety.

Modern protective equipment and air respirator can protect firefighters in an extremely complex environment while firefighters are working in the building.

However, when the gas in their gas cylinders was exhausted, they also had to take off the empty face mask.

At this time, if the building is filled with high-temperature fire smoke, the firefighters will have the same breathing difficulties as those trapped due to the effects of poison and heat. In this case, if the smoke is discharged in time, it can be avoided. A lot of trouble.

When firefighters can see the situation around the fire, the safety factor will greatly increase.

The smoke exhaustion can solve this problem, but the exhaust smoke must be mutually complementary with the fire extinguishment, and it should be completed as soon as possible to help firefighters conduct effective search and rescue.

Third, assist firefighters to carry out skirts

When firefighters arrive at the fire, they are often ignited by smoke on the fire, and hot air mixed with flames rushes out of doors and windows. More often, they need to enter a room full of dark smoke and high temperatures.

Although the visibility is poor and nothing can be seen, they still need to lay fire hoses, and through the guidance of walls and floors to explore the dark, high-temperature fire.

Before the smoke evacuation personnel discharge the toxic fumes from the room and send fresh air to the roof, the attack speed of firefighters is usually very slow.

When seeing the fire, the firefighters turned on the water gun to extinguish the fire, which would have a certain control over the spread of the fire and reduce the indoor temperature to a certain extent, but at the same time generate a lot of water vapor.

The increase of water vapor will reduce the buoyancy of various combustion products, reduce the amount of smoke discharged from the roof smoke outlet, and is not conducive to the emission of smoke.

In spite of this, the water will reduce the fire extinguishing temperature and reduce the amount of smoke in the fire water.

For better results, the smoke exhaust should be ready when the firefighters enter the building and begin implementation.

As mentioned earlier, efficient smoke extraction must be coordinated with the outflow attack.

Fourth, it helps to quickly locate the fire point

Before the firefighters extinguish water, they should first determine the location of the fire point. Sometimes, firefighters fire out of water because they saw the smoke, but it is generally believed that the most effective method of fire fighting during a fire should be to see the fire and then out of the water.

But in a smoke-filled, high-temperature environment, firefighters usually take a long time to see the open flame.

In the case of limited field of vision, the class will not be able to make any sacrifices.

They explored through dark passages and rooms, and judged the point of ignition by feeling the change in temperature. Fortunately, in the end they could see a predictive orange flare and confirm the fire point.

However, this will slow down the firefighters' positioning of the fire and keep the firefighters in a dangerous environment.

If high-efficiency smoke emission can be implemented early in the fire, the situation will be greatly improved. It will not only protect firefighters from the threat of high-temperature and toxic smoke, but also help to quickly discover the location of fire and quickly control the fire.

Strategic design, timely and reasonable smoke emission, prevention of smoke and heat to threaten firefighters, and control of the fire in a certain area, so as to truly accelerate the fire fighting action.

Fifth, reduce the speed of flame propagation

In a building fire, the fire spreads horizontally and vertically and ignites the combustibles encountered during the spread.

Exhausting smoke from buildings can hinder the spread of fire in two ways:

First of all, exhaust smoke can emit heat. Exhaust of heat can reduce the likelihood of combustibles being ignited. Every 10 °C decrease in temperature can reduce the chemical reaction rate in the combustion process by 50% .

Second, proper smoke extraction can spread the fire along the route determined by the firefighters, or spread through the natural smoke vents and openings opened by firemen.

For example, when the roof has an opening, due to the high indoor pressure, various combustion products are forced to move from these openings to the lower pressure external environment.

In modern building fires, large amounts of heat are generated due to the extensive use of synthetic materials. If heat is not discharged in time, it may spread the fire to other areas.

Six, help to reduce property loss

After the fire, there will be a lot of smoke marks on personal items, internal buildings and windows. High temperatures can melt or deform plastics, internal devices, circuits, and other items.

Protecting property is an important part that fire fighters should pay attention to, and a small fire may also generate enough smoke to permeate the entire building.

In the early stages and development stages of the fire, effective exhaust smoke can greatly reduce the losses caused by smoke and flames. At the same time, if firefighters can quickly find the point of fire, they can also reduce water damage.

Author Armed Police Academy Li Sicheng