Air Vent Passageway / Anime & Manga

• In "Turnabout Prophecy" of the Ace Attorney manga, this is averted. The ventilation pipes themselves are too small to crawl in, but it is possible to crawl in the area where the pipes are.
• In AKIRA, Kaneda tries to escape custody through the ventilation duct. He doesn't get far though.
• Amusingly downplayed by Jody Hayward in El Cazador de la Bruja. She uses the vents to sneak into Rosenberg's office only to find that her hips are slightly too large to fit through them.
• In Aggretsuko, Retsuko and Kabae use the air vents to infiltrate the office and spy on Haida, complete with a "Mission: Impossible" Cable Drop.
• Cells at Work!: In the very first chapter/episode, White Blood Cell rescues Red Blood Cell from a Pneumococcus in an alveolus (depicted as a small storage room) by appearing through an air vent on the ceiling.
• Ryō and Saeko sneak into a jewel exhibit this way in City Hunter. Ryō gets a heel in his forehead as a reward for his overly ardent Male Gaze.
• Justified on two occasions in Dance in the Vampire Bund.
  • Akira making it through the massive vents and tunnels of the underground city beneath Tokyo Landfill #1 to escape the assassins hunting him makes sense (and he finds himself reminding his prepubescent rescuers that he is not as compact as they are).
  • In an inversion from volume 7, after a Manchurian Agent locks down Mina's skyscraper-cum-palace the only person who can get to the security center via the way-too-small-for-anything-remotely-human vents is Vera (who turns into mist and is obliged to leave her clothes behind).
• Doraemon
  • One of the anime episodes have Doraemon using his gadget-of-the-week microchip to revive a toy robot, who then infiltrates Gian's house via the vent while carrying a box of microchips, meant to revive Suneo's robot toys as well (stolen by Gian as usual) and have them leaving Gian's house en masse.
  • Doraemon: Nobita's Secret Gadget Museum have Suneo and Gian infiltrating the museum's underground lab through a vent, compared to Doraemon, Nobita and Shizuka who uses a secret entrance. Partially justified because Gian and Suneo had accidentally shrunk themselves with the Gulliver Tunnel and are the size of dolls.
• In Dragon Quest: The Adventure of Dai, Maam, after breaking out of her jail cell, evades the undead monsters in the underground dungeon through one such passageway. She's able to squeeze her way through it, though she remarks that either the hallway is getting narrower and narrower or she might need to go on a diet.
• Justified in Excel♡Saga in Kabapu's underground base; as Dr. Shiouji pointed out, they have to be big in order for any sort of air to move though such a large place underground.
• While searching an enemy ship in Fairy Tail the Exceeds (who are about the size of a cat) are shown crawling through an air vent, wondering about the necessity of it and complaining about how narrow it is. When they ask why they're in there instead of searching the rooms like a normal person, Happy says "No particular reason".
• Food Wars!: Satoshi Isshiki has a habit of crawling through the Polaris dorm attic and removing ceiling tiles to talk to his dorm-mates.
• Franken Fran has to cut off at least half her body in order to pull off a vent escape.
• Justified in Fullmetal Alchemist: shrimpy Edward is the only character who can fit in the air vents, and even for him it's a tight fit. Which leads to further comedy as Ed has a complex for being The Napoleon. Ed acknowledges that it's lucky he's so small, otherwise he wouldn't be able to fit... and promptly gets mad that he called himself short.
• Futari wa Pretty Cure episode 10. Nagisa needs to get into a store being robbed so she can meet Honoka, since they have to be together to transform. Extra points for doing it in the course of about five seconds with no equipment.
• In G Gundam's second episode, Domon sneaks through the ducts of Madison Square Garden and ambushes Chibodee's boxing opponent so he can take his place. In the 2010 manga re-telling, the sequence is Played for Laughs instead: Domon intends to go to Chibodee and challenge him, but ends up in the opponent's room because he got lost. He then tries to play himself off as an autograph hound. It doesn't work, and after knocking the guy out he decides to take his place.
• Mamoru and Volfogg do this in GaoGaiGar when their base is taken over by a computer-hacking Zonder. Mamoru is a nine-year-old, but Volfogg is a robot that transforms into a police car.
• Ghost in the Shell: Stand Alone Complex:
  • Like the opening of season 1, the opening of season 2 is all about showing off the awesome skills of Section 9 while providing a reason for the unit's reactivation. The regular SWAT unit attempts an assault on the Chinese embassy through the air vents, but spectacularly fails with one officer dead and another being added to the terrorists' hostages. Seeing these poor results, his superiors immediately give Aramaki the green light to send in his team and get the job done.
  • When Batou is snooping around in Zaitsev's office, he hides in the ducts when Zaitsev returns unexpectedly.
  • 2nd GIG episode "Ambivalence". Major Kusanagi physically breaks into the Cabinet Intelligence Agency's building to cyberhack into its Decatonchire server. After the Big Bad Goda discovers the breach and alerts security, she escapes the building by entering the air system via a opening in the ceiling.
• Gunslinger Girl
  • A simpler version happens in Chapter 3 when Marco takes out a terrorist cell by throwing a flash-bang grenade into their air vent before just walking in the door.
  • When terrorists take over a nuclear power plant, the Agency sends some of their cyborg child soldiers through a sewer pipe which unfortunately has heat sensors that tip them off. Triela cuts her way out of the pipe and is immediately ambushed with anti-material rifles.
• Hellsing:
  • Integra does this to hide from her uncle.
  • Seras and Walter also use this to avoid a confrontation with the Valentine brothers.
  • Walter actually makes a point of reminding Integra that she used the vents to hide, so it's possible that they were deliberately designed with the purpose of allowing people to move throughout the mansion and avoid enemies in mind.
• In Hetalia: Axis Powers, Paint it White!: Italy, Germany, and Japan pull one of these in order to escape the aliens currently chasing them. May or may not be justified because they were in an alien mothership, with air vents about the size of an average person. They DID fall through at one point, and Germany got quite a few scratches to the face.
• Done in Hunter × Hunter, though the character doing this (Queen Oito, after Kurapika grants her Nen abilities) is mind-controlling a cockroach, making it more plausible than normal. The cockroach finds Prince Tserriednich's Nen Beast within the ducts, forcing Oito to perform a quick mind-recall back to herself before the Nen Beast eats the cockroach.
• In JoJo's Bizarre Adventure: Battle Tendency, the Pillar Man Santana manages to get through a 4-by-20-inch, grate-covered vent by pulverizing every bone in his body and flattening himself until he can slip through. Thereafter, the Nazi research team does not live long enough to learn that Evil Is Not a Toy.
• In Mission: Yozakura Family, the Yozakuras often find themselves entering and leaving facilities by crawling through the air ducts in classic spy fashion. But the story points out how cramped these things usually are, and the Yozakuras are trained to dislocate and relocate their own bones at will in order to fit. Unfortunately for Taiyo, he's not nearly as well-trained and recoils in pain when he performs a Dramatic Dislocation.
• Subverted with glee in Mnemosyne: Slender (though busty) Action Girl Rin Asougi decides to infiltrate an empty research laboratory by going through the ducts. She predicts the lasers and makes them visible by filling the cramped ventilation duct with smoke from a cigarette, and then proceeds to slip under the lasers... until her butt catches the laser, setting off all the alarms. Cue Rin's capture and... Squick.
• In Monster, Johan and Anna/Nina's mother escapes through a rather small-looking air vent not just pregnant but in labor.
• Neon Genesis Evangelion: Asuka, Rei, and Shinji were forced to use this route to get into the Geo-Front during a power outage when none of the doors would open. The air vent entrance also lampshaded the Male Gaze when Asuka kept kicking Shinji for "looking ahead." Later in the episode, we are treated to the sight of Humongous Mecha escaping via (humongous) air ducts. The geofront itself is an immense underground open space, hence the need for extremely large duct shafts to the surface to keep the air fresh.
• Done once in Rave Master though by a creature who must be light, because he floats when he sleeps, and something that may be a small dog.
• In Shugo Chara!, Kiseki and Yoru escape from a locked room this way. Justified since the Shugo Charas in that series are small enough to fit in normal air ducts.
• Successfully done by Tsukiyo in The World God Only Knows, but small as she is she still couldn't have pulled it off normally. Rather, she was shrunk down to the size of a doll and it was still a pretty tight fit.
• Mokuba Kaiba once escaped from the Big 5 this way in Yu-Gi-Oh! At least he's a fairly small kid, more likely to fit and all that.
• A variation in Yakitori: Soldiers of Misfortune when a swarm of Barkan rebels tear their way out of the sewerage pipes to attack Unit K-321, who are suitably grossed out.
• In Yu-Gi-Oh! R, Jounouchi and Honda avoid some Mooks this way. Lampshaded by Jou, who complains about how claustrophobic it is and keeps getting accidentally kicked in the face by Honda.
• In Yu-Gi-Oh! ARC-V, a few characters escape from prison this way. It takes them a while to remove the grate and the fans inside, and a guard catches them, but they manage to bluff that they had been ordered to repair it.