The use of high-power foam in underground space fires

High-power foam extinguishing agent

High-expansion Foam

In underground space fires, high-rate foams are always referred to as disposal methods (Fig. 4-40 ). As mentioned before, high-power foams can replace water gun positions and, in most cases, can be relatively Far and safer area operation, it is safer for firefighters.

(Figure 4-40 , high-power foam is used in underground space fires or other fire scenes where fire fighters are too dangerous. High-rate foam fire extinguishes the space in the fire area to cool and replace the smoke and oxygen in the fire area.)

High-strength foam refers to a mixture of water and additives that can be extremely swollen (expansion ratio between 400 : 1 and 1000 : 1 ). Its main function is to fill the space to drive the combustible material out of the combustion space and replace it in the space with a water fire extinguishing agent that can cool the fire source.

The high-power bubble was initially used as a defensive tool when firefighters were forced out of the fire. We always dream of suppressing the fire after the house that is about to be burned into a high-powered bubble. However, the reality is that when high-rate foams are used, most of them have been too late to be saved. When the attackers in the basement are withdrawn, it is very likely that the first floor personnel will also need to withdraw. As a result, the withdrawal of the upper layers of the fire will result in the long-term spread of the fire, resulting in the collapse of the entire building. Therefore, when using high-intensity foam to inject underground space, it is necessary to provide a longitudinal outlet in the upper part of the fire, preferably in the position opposite the entrance of the high-intensity foam, so that heat, smoke and flame can be properly discharged from the site after being pushed by the foam.

Just as when operating a water gun into a confined space, it is also necessary to provide effective exhaust ventilation when using high-power foam, otherwise the fire tongue will spread along the pipe or crevice itself. If firefighters fail to extinguish these spreading fires, the construction situation will deteriorate.

However, if the on-site situation results in the inability to safely open the fume extraction space in the above space, the on-site commander must recognize that the on-site situation may develop into a serious loss. In this case, if high-powered bubbles or other methods succeed in repressing the fire, then we will win. If we do not succeed in repression, it does not mean that our actions have failed. We can only say that we are equal. Because the building fire prevention department and others such as architects and building owners agree that the fire load in an unventilated confined space without an automatic sprinkler system will be very large.

To use high-power foam to extinguish a good fire, the following principles must be followed (Figure 4-41 ):

1. You must set the position as early as possible when you realize that you need to use high-power foam to extinguish the fire so that you can take advantage of the opportunity to avoid the collapse of the upper floor.

2. It must be ensured that a sufficient number of foams are arranged at the same time. Because the flames and heat will destroy a lot of bubbles, and most of the bubbles will go to a room that has not caught fire.

3 Finally, the high-power foam generator must be placed close to the ignition point. If the fire point is too far away from the bubble generator, the obstacles and doors and windows will be obstructed between the bubble and the fire point. We may need some time to realize that the bubble has no effect. If we then move the bubble generator, it may be Will miss the opportunity to extinguish the fire.

(Figure 4-41 . To ensure that high-power foam can successfully control the fire in the basement, multiple steps are required to be carried out at the same time, including ventilating and exhausting the smoke above the fire point, preventing the fire from spreading vertically, etc. If the superstructure on the fire floor is unstable, then these Actions also become insecure.)

At some point, high-power foam does not completely eliminate the fire. If the basement has a good structural stability (such as reinforced concrete construction), fire fighters can be sent into the interior to destroy the residual fire after using high-power foam to suppress the fire. In those buildings that were forced to evacuate without thorough personnel search, it was necessary to send personnel to the fire scene. For those commercial buildings that had been completely spotted and the stability of the housing, they should continue to pour high times. Foam extinguishing agents to ensure that the firefighters continue to carry out fire extinguishing work in the event of personal safety.

In high-foam bubbles, sounds are blocked. When wearing an air respirator into a foam environment, the sound can only pass 3-4 feet .

Another problem is that the foam forms a protective thermal barrier, which sometimes puts firefighters in the foam environment at risk. If the firefighters use the misty water flow to continue the deep attack, it may damage the heat insulation protection of the foam. At this time, when the water touches the high temperature layer, the water will instantly vaporize, causing the internal attacker's steam to burn. Therefore, firefighters can enter high-foam conditions only in the following situations:

1. Extinguish fires in order to save people or determine the safety of the housing structure.

2. The entry personnel must wear a positive pressure air respirator and open a PASS (personal alert safety system ) to advance along the hose or lifeline and maintain uninterrupted contact with outside personnel. The leader of the internal attack team must use a pull hook or other tools to gradually explore the road to avoid falling. When you move slowly, you must step on each step. It is best to choose to crawl, but pay attention to the dangers of the surroundings. Because the insulation effect of the foam makes you unable to perceive the high temperature in the close range, it is possible that the top of the head is the flame and you are shocked. I do not know.

3. At the starting point of the attack, it is ensured that there is another rapid reaction team ( RIT , rapid intervention team ) ready to respond to unexpected situations.

If you enter the internal fire extinguishing, you must fill the hose before entering, and only use columnar jets or small-angle jets in the interior. When you advance, you must shoot the ceiling above to reduce the residual hot air that cannot be discharged by the high-expansion foam.

Article Source: AndyC 's Cottage WeChat Public Account