Page 1317 - Enders_Game_Full_Book

But he walked past his bunk and quietly sank down and slid under the last bunk, where the uncovered vent awaited him. His towel remained on the floor under the bunk, so that if anyone woke enough to notice that Bean's bunk was empty, they would see that his towel was missing and assume he had gone to the toilet.
It was no less painful this time, sliding into the vent, but once inside, Bean found that his exercise had paid off. He was able to slide down at an angle, always moving slowly enough to make no noise and to avoid snagging his skin on any protruding metal. He wanted no injuries he'd have to explain.
In the utter darkness of the air duct, he had to keep his mental map of the station constantly in mind. The faint nightlight of each barracks cast only enough light into the air ducts to allow him to make out the location of each vent. But what mattered was not the location of the other barracks on this level. Bean had to get either up or down to a deck where teachers lived and worked. Judging from the amount of time it took Dimak to get to their barracks the rare times that a quarrel demanded his attention, Bean assumed that his quarters were on another deck. And because Dimak always arrived breathing a little heavily, Bean also assumed it was a deck below their own level, not above -- Dimak had to climb a ladder, not slide down a pole, to reach them.
Nevertheless, Bean had no intention of going down first. He had to see whether he could successfully climb to a higher deck before getting himself potentially trapped on a lower one.
So when he finally -- after passing three barracks -- came to a vertical shaft, he did not climb down. Instead, he probed the walls to see how much larger it was than the horizontals. It was much wider -- Bean could not reach all the way across it. But it was only slightly deeper, front to back. That was good. As long as Bean didn't work too hard and sweat too much, friction between his skin and the front and back walls of the duct would allow him to inch his way upward. And in the vertical duct, he could face forward, giving his neck a much-needed respite from being perpetually turned to one side.
Downward was almost harder than upward, because once he started sliding it was harder to stop. He was also aware that the lower he went, the heavier he would become. And he had to keep checking the wall beside him, looking for another side duct.
But he didn't have to find it by probing, after all. He could see the side duct, because there was light in both directions. The teachers didn't have the same lights-out rules as the students, and their quarters were smaller, so that vents came more frequently, spilling more light into the duct.
In the first room, a teacher was awake and working at his desk. The trouble was that Bean, peering out of a vent screen near the floor, could not see a thing he was typing.
It would be that way in all the rooms. The floor vents would not work for him. He had to get into the air-intake system.