The tunnel in Cave 2 had been widened in two months, and thanks to the hard work of the Marines, who had been busy for more than a week with detonators and pickaxes, the passage was completely widened. You must know that in the past tunnels, it was really a sideways hard plug, and it was barely able to let people pass.

As he walked forward in the tunnel, Liszt raised his head slightly in surprise, and a cool air caressed him, blowing towards the cave behind him. Licking the corners of his mouth gently, he looked up at the mouth of the Rong Cave with a little light, and couldn't help but nod slightly: "This wind feels really good." ”

The cool air made people feel a sense of relaxation, and the continuous wind seemed to push the otherwise dull air in the tunnel, bringing the freshness of the heavy snow outside. Slightly tilted his head to look ahead, there was also a little cheer at the end of the tunnel, and the corners of Karl's mouth were also curled, and he nodded with a slight smile: "It seems that our No. 4 cave and the exhaust system have also been set up." ”

"Well, this wind seems to be able to meet most of the air needs."

Underground fortifications will always be equipped with a large number of ventilation holes, and Liszt agrees with this. When he came to these caves, he could feel a noticeable suffocation, and there was a strange smell in the air. Especially with the influx of soldiers into a cave, shortness of breath sometimes occurs.

This is undoubtedly a lack of oxygen, and it also shows that the original cracks in these caves, the vents leading to the outside, are not enough to breathe so many people. I see that I have some difficulty breathing in my daily life now. As soon as the war broke out. Covered by artillery fire, some of the ventilation holes were blown down. At that time, it will not only be a problem of breathlessness.

This is also the task that Liszt must complete when preparing to renovate the cave, and the important level is directly at the forefront. After all, he can exchange it for clean drinking water or delicious food, because after the blockade of this mountainous area, there is no way to buy and transport supplies, and can only be made up by exchange or a small amount of self-sufficiency.

But human beings depend on the ubiquitous air in almost the entire space, and he does not have this extravagant behavior to exchange. Despite the availability of diving or medical oxygen. But now it is obvious that as long as a few openings are opened to the outside world, borrowing the ventilation function of the original tunnel, the method of breathing can be smoother, which is much more convenient than directly exchanging air.

"Is this widening the tunnel? But it's also a little too big. ”

As soon as he walked out of the passage, Liszt saw the soldiers who were still busy in front of him, they were all holding hands with each other, carrying the sandbags that seemed to be full, and he looked at the hole about two meters in the rock wall, and couldn't help frowning slightly: "Where did this wind come from?" ”

He could feel the slight cool air blowing gently through the hollow that had been hewn out. After a few turns in the No. 4 cave, it continued to blow into the cave group along the passage. But he looked at the rock wall that was still being excavated. The rock wall has been excavated close to four meters, and it seems that the amount of work has been going on for a long time.

The members of the Marine Corps also had a very clear division of labor among themselves, and with the hoe wielding inside, the rock wall that had been blown by the detonator was chiseled, and the large and small gravel also slid to the ground, and was loaded into sandbags with shovels by other soldiers, and then picked up by other soldiers and quickly carried away, walking towards the tunnel of Cave No. 5, and there was also a tacit understanding between them.

"They threw rubble underneath the cliffs of Cave Five."

With a smile on his face, Carl immediately took out his notebook in his arms for Liszt's question, turned a few pages and quickly handed it to Liszt, pointing to the model on it and explaining: "The vent we found belongs to the windward position, which simply widens the space inside, and can fill a large amount of air anytime and anywhere without the need for an exhaust fan." ”

Frowning slightly, Liszt looked at the figure above, a large machine-like thing, filling the excavated rock wall. Carl was also very matter-of-concern, and said with pride in his tone: "The next plan, we plan to widen the tops of all the cave tunnels, leaving room for the installation of exhaust systems and wiring!" ”

"Central air conditioning?"

Liszt's eyebrows were slightly raised, he looked at the pipe on the notebook, and his memory immediately came to mind the central air conditioning in the office or in a large shopping mall. This kind of machine, which can be controlled to meet the most basic oxygen needs, and can deliver large amounts of air into a closed environment, is undoubtedly in line with the needs of today's karst cave complex.

He carefully looked at the drawing that had been sketched in pencil on the notebook, and the ventilation ducts had spread all over the cave group, and all the ventilation holes had been connected. But his brows were still slightly furrowed, and he looked up at the hole that was still being excavated, and couldn't help asking: "This doesn't seem to be a complete central air conditioner?" ”

Carl also nodded, he also carefully analyzed the surrounding terrain for this ventilation system, and came to a scientific conclusion, very proudly pointed to the line in the notebook and said: "The consumption of central air conditioning is too large, and we are very passive for the current energy output" He said, also paused slightly, and continued: "But the entrance to the cave where we are is is downwind of this mountain valley, and there are mountain winds blowing all year round, so why not use their own strength?" ”

Looking at the lines outlined in the notebook, Liszt couldn't help but praise Karl, a high-achieving student, just borrowing the mountain breeze from the outside world and using the pipes connecting all the caves as a medium to complete the ventilation function of the central air conditioner. And as long as this project is completed, the ventilation problem in the cave has basically been solved.

"Something out of the ordinary!"

But while the two were still talking about the central ventilation system, a Marine Corps soldier quickly ran through the tunnel of Cave 5 with a gun. Although he was a little out of breath, but there was not much panic on his face, he rushed out of the passage, saw Liszt and Karl not far away, and also walked over and saluted sharply: "I found that the Canadian troops were heading towards our area, the standard reconnaissance team, I didn't find that I was carrying heavy firepower, and I didn't find that there was helicopter support in the air!" (To be continued.) )