Reading the Fire Site is an Art - Talking about the BE-SAHF Fire Assessment Model

01 Introduction

Firefighters have fought with the fire for more than 200 years. During this long period of time, people have been working hard to improve the methods used to extinguish fires. One of the fire extinguishing skills is of particular importance. It is fire field identification technology.

A fire is a chemical reaction that is out of control in a particular environment. It is not a creature that can sense the surrounding environment, nor can it make any choice on its own initiative.

The nature of fire is determined by the physical and chemical nature. The mutual influence on the surrounding environment is determined by many different factors. Each of these factors can be described in a scientific way. When many factors work together, the final result becomes extremely complicated.

Now, there is a computer program for calculating fire characteristics. In most cases, a lot of simplifications have been made in these fire calculations.

In addition, many high-end computers require a week or two to determine the development of a fire within 10 minutes.

It can be said that it is possible to scientifically judge fires, but this requires investing in computers for a large number of calculations. In other words, fires are also predictable.

Humans do not have as much computing power as computers, but it is possible to observe fires and draw some conclusions from them, and thus predict fire characteristics.

What needs to be reminded is that although we can predict fires through the above methods (identifying the fire scene) many times, this is not always the case.

Identifying the fire is a science and an art.

This is because in the field of fire, many information is not easily available, or you can rely on computers to make accurate predictions.

The fire field's prediction and evaluation is based on the information collected during the fire reconnaissance. In other words, the predictability of the fire in the fire field is limited.

Experienced firefighters will better interpret the fire. Firefighters can become very skilled by conducting regular fire field identification training and actively attempting to apply the technology to the fire scene. This also helps to make decisions in the fire field in a short time.

Scientists have always believed that the decision on the fire field was made by comparing the current fire assessment with previous experience.

This is the so-called recognition priority decision ( rpd = recognition priority decision).

1. History

Shan Raffel is an Australian firefighter. Since 1983 , he has been active in Brisbane with 2.5 million residents. He is now the commander of a fire station.

In early 2000 , he was the first to think about using a model to judge the fire.

He named his model SAHF , which is an acronym for the four English words: smoke, air flow, heat, and flame.

Subsequently, this model was introduced to the Netherlands by Edward Huize . In 2000 , Belgium introduced the model through the Dutch Fire Department.

Shan Raffel is a member of the IFIW (International Fire Instructors Seminar). Scientists and experts from all over the world use IFIW as a platform to share knowledge about fire characteristics and fire fighting. Here, the SAHF model has been recognized by some international experts.

Very quickly, there were some disagreements on certain signs described by Raffel 's SAHF model, such as paint foaming, cracking of glass windows, etc. These were the subject of controversy.

Stefan Svensson of Sweden stated that he has never experienced these phenomena. However, Shan Raffel saw these signs in the developmental fires in Australia.

The United States Fire Department Director Ed Hartin proposed a solution to this problem. He prefixed SAHF with B (for architecture).

Ed Hartin said that the evaluation of the SAHF signature should not be separated from the building where the fire spread, and the building is the basis for the evaluation of the fire signature.

In 2008 , Shan Raffel upgraded his model to B-SAHF .

Under the influence of Karel Lambert , a Dutch acronym, G-RSTV, was born. The widespread use of Siemco Baaij in the book “ Brandverloop ” spread the word in the field of firefighting.

In about 2009 , firefighters in North America discovered wind-fighting.

Studies have shown that under the influence of strong winds, the characteristics of the fire may be fundamentally changed.

However, after many years, people fully realized the seriousness of the problem and many firefighters sacrificed it.

In most cases, these accidents occurred in the upper floors of high-rise buildings, which also led to a misconception that wind-driven phenomena only occur in high-rise building fires.

Until one time, a young firefighter was sacrificed on the first floor of a common house to eliminate the misunderstanding of wind and fire.

Peter McBride of Canada suggested updating the model again. Specifically, he suggested that after the "B-SAHF" in B plus E, E on behalf of the environment.

The idea is to separate the wind from the air flow trajectory and pay special attention to it. After all, the wind will have a very serious impact on the fire.

In 2014 , Shan Raffel decided to change his model to BE-SAHF .

02

Firefighters using the model have a specific goal: They want to find out how the fire will develop in the next few minutes.

This can be achieved by integrating the fire state of the fire and the ventilation characteristics of the fire into the BE-SAHF model.

Through a comprehensive analysis of these three factors, it is possible to make predictions on current and future potential fire phenomena. But this is only an assessment and it cannot be overly dependent.

Because there are often some important factors in the fire field that are not immediately detected by firefighters, this may lead to conclusions based on the above method may be wrong.

Both the BE-SAHF model and the fuel-controlled and ventilation-controlled models are designed to help fight indoor fires.

The fire field recognition model is mainly applied to the fire of a building composed of many small rooms. For larger rooms, such as open offices and factory buildings, these models do not apply.

When applying the BE-SAHF model, you must first answer the following questions:

2.1 How did the fire develop?

There are two kinds of fire characteristics. When the ventilation conditions are good, the fire will develop to the flash fire stage. After the flashover, firefighters will face a full-blown fire, which is characterized by flames coming out of windows and other openings.

This type of fire development is called ventilation   After the fire, there was enough air in the building to cause flash fire.

The second type is that the doors and windows are closed, that is, ventilation is limited, and only the indoor oxygen supply flames burn.

A closed room will lack oxygen as the fire progresses, and it is limited by ventilation before the flashover occurs. Then it will through the fuel control / ventilation control point (FC / VC point).

Firefighters are faced with smoke-filled buildings. There are few flames and smoke emerges from cracks. The development of this type of fire is called a ventilation-controlled fire, that is, there is not enough air to develop a flash fire.

All models are not exactly correct, but they have implications: Ed Hartin

It should be noted that both the fuel-controlled and ventilation-controlled fires are theoretical fire models, which means that they are not 100% accurate, but they are still useful for the fire.

This is what Ed Hartin mentioned above. Both of these models cover most of the fires, but it is important to realize that these models are not very practical for large space fires. For example, industrial building fires.

Another fire that differs from the above is the building structure fire. This type of fire, the building itself is burning. An example here is that fire burns independently in a concealed space in a building.

The characteristics of this fire are very different from the two typical fire models.

This also means fighting fires of this type and using completely different techniques and methods. Firefighters must recognize this and choose the right method.

2.2 What is the current state of fire?

The development of fires can be either fuel-controlled or ventilation-controlled. This can be easily determined by observing the burning of the flame.

It should be noted that a fire can occur in multiple rooms. It may be that the fire in the kitchen begins to spread into the living room, which means that the fire in the kitchen has become a type of ventilation control, and the fire in the living room is still fuel-controlled.

It is also possible that we are fighting two unrelated fires ( such as arson ) that occur in two unconnected rooms . In this case, the two fires will develop independently of each other.

When a fire is in a fuel-controlled combustion state, the possibility of a flashover must be considered. On the other hand, in the ventilation control state, the stage of fire development and ventilation must be considered.

Only based on these two aspects of information can make an accurate assessment.

2.3 What is the current stage of fire development ?

After the fire broke out, the development of the fire ( good ventilation or poor ventilation ) and the state of combustion ( fuel control or ventilation control ) have been determined and the stages of fire development can be determined.

Fire to what extent? What are the specific risks have disappeared, what are the risks still exist? In the near future, we will face what risk?

Experienced firefighters can determine the type of fire he is facing by assessing the different signs that appear on the fire.

2.4 Where is the fire point ?

After determining the state of the fire, the next thing to do is to find the point of fire. Under normal circumstances, according to the above fire characteristic mark, the location or location of the fire can be evaluated.

2.5 What happens next ?

The following information has been collected :

• Types of fire development

• The state of fire in the fire

• The current stage of development of the fire.

Ventilation conditions, as well as possible changes in the situation, can also have a major impact on the fire.

Using the information described above, a trained commander will be able to assess how the next fire will develop.

It can help him to make the following judgments:

1. Assess risk (information is more important than hedging)

2. Determine tactical goals

3. Request reinforcement and raise fire rating if needed

When the firefighters do nothing, the fire will naturally develop according to the law. The development of the fire was determined from the beginning.

In other words, fire does not "select" a particular way.

However, the purpose of the fire brigade is to control the fire, rescue any potential victims and save property. Firefighters can perform many different tasks and actions to achieve these goals.

The BE-SAHF model can also be used to assess the impact of firefighters on the fire development.

These changes in fire development have both positive and negative aspects. Similarly, in both cases, a trained commander can use the BE-SAHF model to evaluate the situation on site.

2.6 Cases

Firefighters arrived at the first floor of an ordinary house where the fire was fully developed.

The deputy squadron leader who arrived at the first car broke off and he was dealing with a post-ventilation fire.

(1) This is a ventilation controlled fire site;

(2) The fire is in full development.

He saw the window of the room fully open. He couldn't see the back of the house, but he could see the danger of the fire spreading to the surrounding buildings.

There is a good chance of a flash fire in the corridor.

The deputy squadron leader must move quickly and the room on the left side of the corridor will soon be consumed by the fire. As long as the fire can be controlled in the first room, trapped persons upstairs will have more chances to survive, of course, depending on the type of floor partition.

He ordered his players to lay two 45 mm trunk lines. He believes that the flow of the two water guns attacks the fire and the fire can be quickly controlled.

  After controlling the fire, the players can safely conduct search and rescue operations. If there is a room on the left side of the hallway, he will first order to search for these places, and then let the player search for the room upstairs.

Laying or extending the mains is not as important as the task above. After all, by correctly identifying the fire, he can assess the fire and whether the vehicle's own water capacity allows the fire to be controlled.

03

3.1 Background

When applying the BE-SAHF model, specific operating methods are used. First, the framework of the fire was established. Buildings are the environment in which all other factors occur.

In most cases, a lot of information about buildings can be seen from the outside. Obviously, hospital fires are very different from ordinary residential fires.

While observing the building, the surrounding environment must be evaluated, and the most important one is to consider the influence of the wind.

Other aspects of the weather may also affect the fire scene. An example here is cold, sub zero temperatures can seriously affect the water supply to the fire.

The four fire signatures ( SAHF ) must be evaluated against the background of the fire. The order in which these signs appear is important.

Smoke is a sign that reveals much about the type of fire. The same is true for airflow trajectories. Compared with the above two points, there is relatively little information about the fire characteristics that heat and flame bring to us.

3.2 Who uses BE-SAHF ?

The specific signs of the investigation of a fire site can be conducted from outside or inside.

The commander (or driver) and the in-house offensive personnel will see different scenarios. They must all be aware that they may see situations that the other party cannot see.

If necessary, important information must be transmitted via the intercom.

Take an example of what happened during the attack. The attack team reported that they had found a fire and started to extinguish. However, externally, smoke is changing rapidly. Smoke increases in volume, the color becomes darker and darker, and it rushes out of the building faster and faster.

In this case, the commander may order internal personnel to retreat because the internal observations are in stark contrast to external signs.

Although the contradictions in the sign of such fire characteristics cannot be explained, for firefighters this undoubtedly indicates an increase in the risk of fire.

3.2 Needs Attention

These four fire characteristics must be considered comprehensively.

No single factor should be analyzed separately, otherwise there will be situations where the judgment of the fire conditions is inaccurate.

By viewing the four flags at the same time, a large amount of information can be collected. This information will help make an accurate assessment of the fire situation.

The evaluation of the fire characteristic sign should be dynamic. It is necessary to reassess the fire characteristic sign within a certain time interval. It is not possible to perform a simple fire assessment only when arriving at the field. "Fire reconnaissance runs through the entire fire"

Firefighters outside will see more fire signals than firefighters inside.

Here is a good example. In an ordinary family home fire, the front door is open. When the fire brigade arrives, very little gray smoke drifts out.

The team commander conducted fire reconnaissance around the fire when the team members laid water hoses, but when the commander scouted for a lap and the players were ready, the fire changed again.

More black smoke emerges from the house, the smoke is thicker, and the flow rate is faster than before. The players started their attack.

However, the driver saw the increasing smoke, the color gradually deepened, and the more and more fluid.

The above example clearly shows that over time, the signs of the fire are constantly changing. This ever-changing phenomenon is a more valuable information, not a single scene phenomenon that firefighters see when they arrive.

For firefighters, it is very important to continuously conduct reconnaissance on the fire site and pay attention to whether these changes are positive or negative.

Using the BE-SAHF model requires some training. After all, many things have to be taken into account at one time, and there is not much time for the fire scene to consider.

Fire is a dynamic situation that is almost constantly changing. Fortunately, you can train on how to identify.

A good way to solve this problem is to watch the video on YouTube . In the video, there is a model for applying and training BE-SAHF . Can pay more attention to the orange rescue WeChat public number, will also publish such video.

Only through sufficient training can the " BE-SAHF " model be used freely in the fire . After reaching the fire, all fire factors will be processed in the subconscious and solidified into the brain.

Edward Huizer called it " SAHF recognition," and a lot of practice will allow you to quickly analyze the situation.

This article is reproduced from WeChat public number: Orange Rescue.