Behind a fire, there is a group of people who immediately walked into the ruins that were burned beyond recognition after putting out the fire. Through clues and clues, they unraveled the cause of the fire and let the ruins "speak".

National Fire Protection Awareness Day
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Fire has burned, water has washed over, trampled on, and even collapsed... What clues are left in the ruins of the fire scene? Behind a fire, there is a group of people who immediately walked into the ruins that were burned beyond recognition after putting out the fire. Through clues and clues, they unraveled the cause of the fire and let the ruins "speak". They are fire cause investigators in the fire rescue team. The task of the fire dispatcher is to restore the truth of the fire to the greatest extent possible and even help the criminal police identify the arsonist. A few days ago, a Zaobao reporter talked with a member of the National Fire Cause Investigation Professional Committee with 21 years of fire investigation experience, a member of the National Fire Investigation Technical Academic Committee of the Fire and Rescue Bureau of the Ministry of Emergency, a member of the Shandong Provincial Fire and Rescue Corps Fire Investigation Expert Group, and a member of the Qingdao Fire Rescue Detachment Fire Xin Zhibin, senior engineer of the Investigation Department, listened to him tell the story behind "Holmes" at the fire scene.

Xin Zhibin investigates at the fire scene.

Xin Zhibin investigates the fire scene.

/ Dialogue /

Spontaneous combustion of battery car batteries is very scary

Reporter: After investigating many fire scenes, you would like to remind citizens which fire hazards in the home should be paid the most attention.

Xin Zhibin: Home fires are easily caused by electrical wiring, household appliances and natural gas . In recent years, fires caused by spontaneous combustion of battery vehicles have become even more terrifying.

Reporter: How to avoid the accident of spontaneous combustion of battery car batteries?

Xin Zhibin: Battery cars must not be charged or parked at home or in the corridor, but outside the building. The battery of a battery car uses a diaphragm to separate the positive and negative electrodes. Once aged or damaged, the positive and negative electrodes are connected and discharged, causing "thermal runaway" and spontaneous combustion, which will then explode and produce a large amount of toxic smoke.

Reporter: What should I do if the battery of a battery car ignites spontaneously?

Xin Zhibin: There is currently no better way. dry powder fire extinguisher has no effect unless there is a lot of water around and the battery is completely immersed in the water. Otherwise, if you find that the battery has spontaneously ignited, you should quickly find a way to escape from the scene, because the gas produced by the spontaneous combustion of the battery is toxic and can be fatal if you inhale it a few times.

Fire scene investigation is very "brain-burning"

"There is always only one truth!" The famous detective Conan in the cartoon often said this.

Our job is not to go to the fire scene and draw conclusions, but to find evidence to prove and determine the cause of the fire, and to summarize experience and lessons. Because sometimes, the truth is not what we see later. "Xin Zhibin speaks very rigorously, a bit like a teacher giving a lecture. Every point is explained very clearly. Sometimes he will repeatedly give examples to explain a professional terminology that non-professionals do not understand.

Fire investigation is similar to criminal police solving a case. Evidence must be found at the scene. In Finding the truth at a fire scene is often more difficult than finding the truth at a crime scene.

Xin Zhibin told reporters that everyone knows that crime scenes must be protected, but fire scenes are often damaged beyond recognition. “Fire scenes are usually damaged beyond recognition. Three levels of damage. The first level of damage is being destroyed by fire, which is the most serious. Just like many scenes of destroying criminal evidence in movie scenes, they are burned by fire. The second level is damage done as a last resort when putting out fires, such as using water. Flush and use dry powder fire extinguishers to quickly rescue the injured; the third level is the damage caused by building collapse. Buildings burned by fire often collapse. "Xin Zhibin said that after these three damages, there were very few first-hand traces left at the scene, making it even more difficult to find the cause of the fire.

After the fire accident, the scene was not only dirty, but also filled with various harmful gases. The air is filled with all kinds of tiny carbon dust. If you don't wear a mask, your nostrils and mouth will be filled with black oil smoke. Xin Zhibin and his colleagues stood in the fire scene, quietly observing the entire scene like in the movie. Every corner is not spared, and small and suspicious traces at the scene must be extracted and returned for technical testing.

Under such circumstances, especially when encountering some difficult investigations, the current popular saying is "script killing", making judgments through various "brain-burning" such as investigation, analysis, reasoning and induction, and "burning" "Brain" is not just a simple guess, but also needs to be confirmed by evidence. Xin Zhibin said that he often carefully rummaged through a pile of ashes layer by layer with tweezers in order to find a small molten bead after the wire was burned by fire, just like archeology. In a rural haystack fire a few years ago, he discovered the metal cover of a disposable lighter from the ashes of the haystack, and finally found the cause of the fire.

The fire control position covers a wide range of knowledge

"The first priority is to determine how the fire started and where it started." By moving from light areas to serious areas, we can understand the spread of the fire more systematically and determine the source of the fire more accurately.

Fire investigation positions are technical positions and require professional learning. "Physics and chemistry are the basis, such as combustion , fluid mechanics , electrical engineering, reactions between chemical substances, etc., and we must also master the humanities and social sciences." Xin Zhibin told reporters that with the development and progress of high technology, it is necessary to More and more scientific and technological means are being applied, which also places higher demands on the professional knowledge and skills of fire dispatchers. For example, three-dimensional modeling of fire scenes, electronic evidence extraction, professional photography and videography, and even during the interrogation process, it is necessary to detect polygraphs and observe micro-expressions like criminal police.

"Many advanced technologies were not available in the past few years, and we need to continue to learn to enrich our knowledge coverage." Xin Zhibin introduced that the three-dimensional modeling of the fire scene is based on VR scene technology, shot by drones, etc. Equipment, shoot and record the entire post-fire scene, and use corresponding software to restore the immersive scene. This retains the original files of the scene for later verification, and also facilitates remote investigations by many experts; the extraction of electronic evidence is also critical, and can be With the advancement of the times, many surrounding surveillance cameras, mobile phones of on-site personnel, household appliances with recording functions, and even the readings of smart meters and can provide effective clues.

Xin Zhibin told reporters that he and his team members participated in two national and provincial industry technology competitions this year, and the subjects involved seven major projects including three-dimensional modeling, on-site mapping, electronic evidence extraction, on-site photography, on-site video recording, and video analysis. Through competitions, experience has been accumulated and the team has been trained.

For the position of fire dispatcher, accumulation of experience is very important. If you want to become a fire investigation expert, you must go through thousands of fire scenes and gradually mature with the increase of experience and knowledge. There is no other way.

There is a saying in the industry that a fire dispatcher who has participated in 100 difficult fire investigation is considered a beginner, and a fire dispatcher who has participated in 500 difficult fire investigation is considered qualified for the job. Only one who has participated in more than 1,000 difficult fire investigation can be considered an expert, and this It may take 5 to 10 years of continuous accumulation. Xin Zhibin, who has 21 years of work experience, has become an expert in the industry. In recent years, he has participated in more than ten major fire accident investigations across the country, including major oil pipeline leaks and explosions, major hazardous chemical deflagrations, major underground mine fires and offshore fires. Accidents etc.

Peeling away the cocoons to find the truth about the fire

Many fire scene investigations are very "brain-burning". Xin Zhibin told reporters about a home fire case he investigated. "Judging from the scene, the fire broke out first near the TV wall. The TV, surrounding TV cabinets, and other equipment were all burned out. The homeowner initially judged that the TV set was on fire due to a short circuit." Xin Zhibin said that on the surface it seemed consistent with the homeowner's statement. In this case, the area around the TV was the most severely burned. No one was at home when the fire broke out, and the possibility of external fire sources was ruled out.

“However, I always feel that TV sets generally do not spontaneously ignite, and there may be other reasons."Xin Zhibin said that he and his colleagues launched a detailed investigation and soon discovered a detail worthy of attention. The homeowner's cable TV cable has a voltage of more than 140 volts. "Normal cable TV cables are divided into four circles. The middlemost copper core conductor is for transmitting signals and carries weak current. It is wrapped with a layer of insulating material. The outside of the insulating material is wrapped with a layer of metal wire braided signal shielding net. The outermost layer is an insulating protective sheath. "Xin Zhibin said that the problem lies in the layer of the signal shielding network. Normally it is not charged, but it is abnormal to have a voltage of more than 140 volts. After investigation, it was found that it was in the amplifier where the cable enters the home. There was contact between a damaged cable and a damaged wire, which caused voltage.

Xin Zhibin said that through a series of subsequent investigations, the cause of the fire was finally figured out. The cable TV cable was plugged into the TV. On the digital set-top box below, the power cord of the set-top box is connected to the ground, forming a complete current process. "The circuit board in the set-top box can only carry 12 volts, and more than 140 volts are suddenly connected, which is unbearable." , it gradually became hot and caught fire, eventually igniting the TV above. ”

Source | Guanhai News/Qingdao Morning Post Chief Reporter Sun Qimeng Correspondent Xu Guangliang

Editor | Yu Xiaoping