The vent in the middle of the dome ceiling, more than 1 meter in diameter, has a round dust cover embedded in the steel plate of the dome, which looks like it is poured in one piece. The mesh of the dust cover is made of steel wire with a diameter of about 1 mm, which is very fine and strong. Inside the dust cover, there is a laser alarm, and above it, is a powerful wall-mounted dust removal device.

Lei Dong adsorbed the suction cup on the ceiling, grabbed the handle tightly with his left arm, hung it in the air with the strength of one arm, gently bent his arm into a ninety degree angle, made a one-arm pull-up, and slowly rose to a position suitable for work, and then it was like growing on the dome, not shaking.

With internal defense data in hand, Beshiliang easily shielded the laser alarm, and the light emitted by the alarm had dimmed. Receiving the thunderous signal of Bei Shiliang, he took out the combat knife in his right hand and inserted it silently into the edge of the dust cover like a quick knife cutting tofu.

Gently turn the combat knife, carefully break a small hole in the edge of the dust cover, then hold the combat knife horizontally in your mouth, and take out the hose scope and protrude through the small hole into the ventilation duct. Thunderbolt had to make sure that there were no vibration alarms installed in the passage other than the shielded laser alarm. If you accidentally get hit, the movement of removing the dust cover is a little louder and triggers the alarm, and it will be too late to cry.

Luckily, there was nothing inside except for a dust collector with a slight buzzing sound but a strong air current. Lei Dong exhaled lightly, retracted the hose speculum, reinserted the combat knife into the small hole in the dust cover, and used the fine serrations on the back of the knife to slash along the edge.

Lei moved his left arm with force, and his body actually pressed horizontally against the dome, constantly adjusting his body posture with the direction of the blade, so that his arm span could reach the edge of the dust net.

After a minute, the dust filter was almost completely broken, leaving only about 30 centimeters of arc still in place. Lei Dong put the combat knife back in his mouth, grabbed the edge of the dust cover and gently pulled it down, and the steel wire mesh bent down, revealing the cave with the god inside.

Lei Dong took out the suction cup of his right hand and sucked it firmly on the inner wall of the cave, let go of the suction cup of his left hand, and his body flashed, and he was close to entering the ventilation duct.

The lower part of this ventilation duct is made of high-strength alloy material, smooth and straight to the outside, turning a corner at a height of more than ten meters and disappearing from the sight of thunder. Lei Dong made a slight observation, and soon found the mouth of the wind tunnel that led horizontally to the interior of the mountain.

Using the same method, he broke through the dust cover at the mouth of the air duct, and thunderbolted into the air duct, and gently tapped three times on the individual tactical radio transmitter to send a signal to the dark clouds.

After a while, the big head of the dark cloud drilled into the main air duct, and his feet reached into the horizontal ventilation duct, so that Lei Dong firmly grasped it, and the body of the dark cloud hung upside down, and gently folded the dust cover of the main air duct back, and after a little treatment, it looked like no one had ever moved his hands and feet, and he supported it with one hand on the rock wall, and Lei Dong used a slight force to pull the dark cloud into the horizontal air duct.

This air duct is about one and a half meters in diameter, and the dark clouds easily turn around inside, follow the thunder, and crawl inside.

The beginning of the transverse air duct is still made of high-strength alloy, which is very smooth and solid, and due to the existence of dust removal facilities, there is not much floating soil in the passage, and two people lie on the ground, using their hands and feet together, swimming forward quickly like a swimming fish.

It was getting farther and farther away from the hall, losing the passage of the hall's light diffusion, getting darker and darker, and finally, at about 200 meters, after turning an "L" bend to the left, the light had completely disappeared, and it was pitch black in front of me. Fortunately, both of them are perverts whose strength is far beyond the limits of human beings, and this darkness does not affect their actions at all.

Turning this "L" shaped corner, the passage in front of it became straight again, but the cave wall was no longer made of alloy, but became a primitive mountain wall, the tentacles were cold and rough, and the dust became thick, and when you reached out and touched it, fine dust immediately flew up.

"!" The flying dust drifted into Lei Dong's nose, almost making him can't help but sneeze, Lei Dong hurriedly held his breath, and shook his head vigorously a few times in succession before he eliminated the urge to sneeze. Lying on the ground and waiting for all the fine dust to dissipate, Lei Dong took a deep breath, then completely closed his breath, used his hands and feet together, and moved forward quickly.

Since entering the air duct, Lei Dong found that the signal from Bei Shiliang was getting weaker and weaker, and finally, only a hundred meters after turning this corner, there was already a meaningless noise from the earphones.

No signal!

After all, it is inside the mountain, and the signal of the tactical radio station is wired, and it is beyond the expectations of Lei Dong to be able to maintain this distance.

Stopping to turn off the station, Thunder moved inside to take a closer look. From now on, even if the two of them lose outside intelligence and electronic support, they can only fight alone.

It took about 10 minutes to crawl forward for about 1,300 meters, and there was another "L" turn in the passage, and Lei Dong knew that it was probably getting closer and closer to the exit of the passage.

Stopping and crouching around the corner, the passage in front of him was no longer a natural mountain wall, but an alloy passage again.

Lei Dong took on the low-light night vision device and looked carefully into the passage.

An important advantage of the artificial ventilation duct is that it is very convenient to hide all kinds of early warning and monitoring equipment inside, which is not easy to find, and it is close to the exit, and the possibility of arranging early warning equipment is very large.

The passage is about 300 meters long, the walls are smooth, and at the end of the passage, a circular dust cover is constantly running, with a slight humming sound from the dust removal equipment. There, that's the exit of the passage.

"Sure enough, there is an independent power supply system!" Lei Dong sighed secretly, and searched more and more carefully, centimeter by centimeter.

From the low-light night vision goggles, it shows a ghost-like film with a little crystal but a strange faint green. Lei Dong first observed the wireless direction finder on his chest, and there was no response at all.

Looking forward again, Lei Dong's gaze was condensed.

About 50 meters away from the exit, Lei Dong found the middle of the cave wall, with two circular protrusions of about one centimeter on each side, and two dark red beams of light, intersecting, dividing the passage into four extremely narrow sections, each of which was less than fifty centimeters wide at its widest point.

Laser alarm!