How can infrared thermal imager play a role in fire rescue?

The use of an infrared thermal imager allows firefighters to determine the temperature gradient at the site of the fire, thereby analyzing the process of fire occurrence, development, and extinction. This is of great value both for firefighting and for investigation of the cause of the accident.

1 , infrared thermal imager works

Any object whose temperature is above -273 °C (absolute zero ) will continuously emit infrared rays due to the random movement of its own molecules or atoms. An infrared thermal imager is a device for detecting such infrared rays that cannot be directly observed and discovered by the naked eye, and its core is an infrared detector. It can receive the infrared radiation of the object and convert the invisible infrared light into an electronic signal. After being processed by the signal system, it is output to the display screen and displays the temperature field distribution image of the target object in gray scale or pseudo color.

2 , the advantages of infrared camera

( 1 ) Wide range of environmental adaptation. The infrared camera can work normally in low light conditions such as visible light, nighttime, and heavy smoke.

( 2 ) Infrared penetrating ability is strong, able to penetrate dense smoke, dense fog, easy to work when the line of sight is not good.

( 3 ) Lightweight and convenient. The instrument is small in size, light in weight, easy to carry, easy to operate and easy to use.

( 4 ) High precision. The image acquisition accuracy is high, and the smaller temperature difference on the fire scene can be distinguished.

( 5 ) The image is intuitive. The temperature distribution of the instrument output image is intuitive, the results do not require further processing, features clear, strong proof.

3 , infrared thermal imager in the fire and rescue applications

Infrared thermal imaging cameras have great application space in firefighting. However, due to the limitations of the infrared thermal imaging camera itself, the scope of its use is also very limited, and it is not as magical as advertised by manufacturers and scientific research. It is necessary to see the essence of the thermal imager through gorgeous propaganda, use its strengths, and use various other traditional methods to make up for its shortcomings, and ultimately achieve the purpose of effectively improving the efficiency of firefighting and rescue.

3.1 Fire Investigation

Fire reconnaissance is all information that the fire-fighting forces obtain about the target of fire fighting. It is the basis for commanders to deploy their missions and fights, and is one of the most important tasks in the entire fire scene. Without the data and information provided by fire reconnaissance, other firefighting and rescue operations lost their direction. However, in our actual combat process, fire reconnaissance is often simply asked and taken a look. There are occasional flies and flies. Even with simple eyes, the situation that leads to greater losses also occurs. . An infrared camera can be used as an aid in fire detection to determine the flame center position, the degree of combustion, and the spread. The on-site commanders and soldiers can observe the fire scene through the thermal imager. According to the information obtained, the fire commander can correctly arrange the force and effectively extinguish the fire.

The thermal imager is best suited to detect fires in the fire. When the fire is completely burning, the fire situation can be clearly judged with the naked eye. The thermal imager cannot obtain more information than the naked eye due to high-temperature smoke and other reasons. Another reason is that the resolution of the existing thermal imager ( 320*240 or 640*480 ) is limited , and the image resolution obtained by the thermal imager is not high enough.

When the fire is in a smoldering fire and the fire is relatively small, the thermal imager can effectively play a role, which is conducive to improving the fire extinguishing efficiency and reducing water loss during fire extinguishing. As shown in Fig. 2 , a cutting shop fire in a small factory. At that time, the factory smoke filled the entire plant. The scene only felt a large smoke, no obvious heat wave. If you use the traditional method, you will waste a lot of time looking for the source of fire, and many obstacles in the plant are more difficult to walk, because at the time the visibility under the bright light is less than 1 meter. However, with the help of the thermal imager, it was obvious to see the roads and obstacles on the side of the building. A hot spot was initially found at about 10 meters, and the fire source was further confirmed. After that, a water gun was used to extinguish the fire within 2 minutes. The entire fire fighting and rescue operation does not exceed 5 minutes.

3.2 auxiliary fire

The thermal imager can be used to assist firefighters in extinguishing fires and judging the roots of the flame through the thermal imager instead of the conventional fire. This can effectively increase the combat fighting ability and extinguish the fire better and faster. However, when using the thermal imager, it is not possible to draw water at the same time, because the colder water flow will significantly interfere with the thermal imager's judgment of the flame temperature and lose its use effect. Figure 3 shows a fire in a wooden house. It can be seen that the open fire is bright white, and the cooler stream is darker in the image of the thermal imager. The thermal imager can assist in the search for fire spots, especially the hidden smoldering.

3.3 Building Structure Safety Inspection

The thermal imager can also perform non-destructive testing on the safety of the structure of the building. At the same time when the fire is saved, the load-bearing parts of the building are continuously tested to determine whether the building has experienced a decrease in strength. Especially in the combustion of large-span steel structures, because the steel structure begins to reduce its strength at 300 degrees, thermal imagers can be used to determine whether the steel structure is safe and where special cooling is required to ensure the plant and personnel. Safety.

3.4 Non-destructive temperature monitoring of fluid level and hazardous source

When no insulation layer oil tank and other tanks are exposed to heat radiation, the thermal imager can easily determine the liquid level of the liquid storage tank because the heat capacity of the tank material is lower than that of the empty tank assembly. It is also possible to test liquefied gas cylinders in tank trucks and fires to determine if there is a risk of explosion from a hazardous source. On the scene of special disasters such as oil and chemical industry, a large number of inflammable storage tanks are stored, making it a high-risk disaster relief site. In such enterprise fires, the data collection of tank temperature and liquid level is particularly important for commander decision-making. The naked eye can not directly see the specific liquid level of petrochemical products and raw materials in the tank. However, when these liquids are stored in the tank, a certain temperature difference will occur because the stored flammable liquid has a larger heat capacity than the empty tank area. With the use of an infrared camera, fire commanders can quickly determine the remaining level in the fire tank and surrounding tank (Figure 5 ), and determine the degree of danger of each tank in order to take appropriate rescue measures.

Similarly, firefighters often encounter liquefied petroleum gas tanks in residential areas on fire sites, but it is difficult to determine whether they will explode in the liquefied petroleum gas tanks in the fire and whether they are completely cooled. Using the thermal imager can easily measure the temperature of the LPG tank and determine if the tank is in a safe state. Figure 6 shows a well-cooled liquefied petroleum gas tank in a fire field.

3.5 Determine the location of the leak

Both liquid vaporization and gas pressure changes absorb ambient heat. It is difficult for firefighters wearing heavy chemical protective clothing to visually observe the condensation of water vapor in the air or hear squeaks. The anomalous changes in heat can be observed with the thermal imager. Therefore, the leak location can be observed to provide a basis for further processing. In addition, in the scene of an accident where there is no light or light, firefighters cannot judge the specific location of the leak just by leaking sound. There is a temperature difference between the leaked gas or liquid and the surrounding environment of the site, so the infrared thermal imager can be used to quickly find the specific part of the concealed leak caused by valve damage, pipeline rupture, or other related equipment damage.

3.6 clean up the fire

In the later stages of the fire, facing the rising steam and smoke everywhere, it is difficult for firefighters to determine where they are really not extinguished (Figure 8 ). A lot of time is spent on blanket cooling, but for smoldering that really needs cooling. The area did not use enough water and time, which often caused the firefighters to struggle. For example in October 2013 occurred in Wenzhou Longgang Faber fire, firefighters huge plant consumes a lot of time and effort to clean up the embers. However, even after three months after the fire was extinguished, some of the remaining fires were not extinguished. The use of a thermal imager to assist firefighters in judging where they really need to cool can be very helpful in reducing the time to save.

In fire suppression, the thermal imager is used to determine the location of the fire, the degree of combustion, and the spread. The thermal imager was used to observe the fire, and the fire was burned and spread to determine the center of the fire. According to the information obtained, the fire commander can correctly lay out the strength and effectively extinguish the fire.

In addition, in the fire field, the water zone can be easily observed in the image of the thermal imager due to the flowing cold water. Even in the fire smoke, it is very obvious. It can help the firefighters to escape quickly in special circumstances and prevent the fire. Lost in the direction.

In addition, infrared cameras can also help firefighters eliminate hidden sources of fire in complex fires. At the scene of a fire, heat is often conducted to other parts through metal pipes or other metal objects, causing other flammable materials to catch fire and expand the fire. In the scene of large smoke and poor visibility, it is difficult for firefighters to distinguish high-temperature objects (such as metal objects, pipes, etc.) by naked eyes. With an infrared thermal imager, it is possible to clearly detect hot objects and take cooling measures in time, or quickly transfer and remove flammable materials.