Air Vent Passageway



""2. My ventilation ducts will be too small to crawl through.""

- The Evil Overlord List

It's the only move on the part of a villain that's stupider than Locking MacGyver in the Store Cupboard (or any room with a bed). When heroes find themselves trapped in a room with all doors and windows locked, the quickest exit is always through the ventilation duct. Air vents also work excellently in reverse for breaking in and infiltrating a facility, as well. Covers require little or no effort to remove, openings are always within reach, they're always able to support the weight of a person even though they were only designed to carry air, they are wide enough in diameter to allow an adult to pass through, there are no internal obstacles like bracing or blowers (except for the occasional menacing giant fan blocking the branching corridors), they are free of normal sheet metal's dangerously sharp edges, they are totally soundproof, and there's never a lack of light or chance of getting lost unless the plot calls for it.

And the escapee always emerges without having picked up so much as a speck of dust.

You'd think the bad guys would eventually learn to design thinner air ducts, or post guards around the openings instead of at regular doors, or line their ducts with barbed wire and broken glass. It even appears near the top of the Evil Overlord List. At least some are smart enough to equip their prison with a surveillance camera, which the hero simply has to smash before making the getaway.

This is practically a Discredited Trope by now, and requires some effort to justify if it's to be used seriously. Which is why it's such a shock that it's actually happened at least once in real life. Frank Morris and his accomplices escaped from Alcatraz by breaking out the grills in their cells and climbing through a maintenance corridor, up to the large ventilation duct that led them to the roof. This escape was later reproduced by Myth Busters. However, on another occasion, Mythbusters did test more standard metal ducts, such as one would find in most buildings, and found climbing around in them impractical at best, along with being very noisy and certain to attract attention (even more so if you've got magnets attached to your hands and knees...). Perhaps the only way this trope is justified is if the character in question has some kind of shrinking or Super Smoke power, in which the physical limitations of an air duct are less of a concern.

One area where the trope isn't discredited is the world of Video Games: Expect almost any game set inside a complex to contain an ample supply of vents, many of which mysteriously just connect two rooms with no fans, grates, branches, or actual ventilation.

Some large universities (MIT and Caltech in particular) have longstanding "steam tunnel spelunkers" clubs, who often use air ducts (among other things) for exploring, getting around campus quickly, or pulling off pranks. Readers of this trope should be advised that this is extremely dangerous, not to mention illegal -- steam tunnels are usually hot, cramped, and frequently criss-crossed by scalding-hot piping, and explorers face trespassing charges and possible academic sanctions if they're discovered within.

However, most attempts to sneak in or out via air duct aren't very successful since people tend to be fairly large and ducts tend to be fairly small, plus the fact that air can bend at ninety degree angles and fit through grates much more readily. There have been numerous cases where enterprising criminals have attempted to rob a store by sneaking through the ducts end up getting stuck. The usual ending is the embarrassed criminal being either pulled or cut out of the duct by the fire department and then promptly handed over to the authorities.

Compare Absurdly Spacious Sewer for a similar trope which takes place beneath buildings rather than in them.

Anime & Manga

 * Justified Trope 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.
 * Like the opening of the first season, the opening of the second season of Ghost in the Shell: Stand Alone Complex 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.
 * 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. Later in the episode, we are treated to the sight of Humongous Mecha escaping via (humongous) air ducts.
 * The air vent entrance also Lampshaded the Male Gaze when Asuka kept kicking Shinji for "looking ahead."
 * 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.
 * And 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.
 * Subverted Trope 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.
 * Ryou and Saeko sneak into a jewel exhibit this way in City Hunter. Ryou gets a heel in his forehead as a reward for his overly ardent Male Gaze.
 * In Monster, Johan and Anna/Nina's mother escapes through a rather small-looking air vent not just pregnant but in labor.
 * 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.
 * 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.
 * Integra does this to hide from her uncle in Hellsing.
 * 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 Shugo Chara, Kiseki and Yoru escape from a locked room this way. Justified Trope since the Shugo Charas in that series are small enough to fit in normal air ducts.
 * 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.
 * 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 even then 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-to-small-for-anything-remotely-human vents is Vera (who turns into mist and is obliged to leave her clothes behind).
 * Franken Fran has to cut off at least half her body in order to pull off a vent escape.
 * 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. Needless to say it doesn't work, and after knocking the guy out he decides to take his place.
 * In Axis Powers Hetalia, 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 due to the fact that they were in an alien mothership, with air vents about the size of an average person. Not to mention that they DID fall through at one point, and Germany got quite a few scratches to the face.
 * 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 their instead of searching the rooms like a normal person, Happy says "No particular reason".
 * 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.
 * Amusingly Downplayed Trope 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.

Comics
"Agent 355: You said we'd be able to use the air conditioning vents. They're six inches by four inches. Yorick: Yeah, well, I overestimated the amount of... air this place might need..."
 * An example of a villain using this trope is found in Marvel's 1990s series Sleepwalker, when Serial Killer Jeremy Roscoe, after freeing himself from his restraints, climbs into the ducts to escape the prison hospital where he was being held. Probably not as bad as some of the other examples, since by that time the alarms were already activated and Roscoe's only concern was getting out by the fastest route possible.
 * Spider-Man does this every now and again. In an interesting variation, however, he usually does it when he's breaking into a place, rather than trying to escape.
 * In the Spider-Man game for the Playstation, Spider-Man has to escape from an underwater base using the air ducts... which are big enough for him to web-swing through. Talk about shoddy design....
 * Kei tries this in The Dirty Pair series Biohazard. But she gets stuck when her full, child-bearing hips won't fit. Mmmm.
 * It's a Shout-Out to one of the TV episodes. Also contains Yuri's wonderful 4th-wall-leaning (slash) Lampshade Hanging from her outside POV: "Been hitting the cheesecake a little too hard, hmm?"
 * Subverted in Y: The Last Man when Agent 355 and Yorick are breaking into a hotel in Sydney (surrounded by barbed wire and armed security due to the increase in drug-related crime after the plague).


 * In a series of Get Fuzzy strips, Bucky tried this tactic to reach the ferret in the next apartment. While he fit fine (because he's a cat) he ended up getting lost and having to call for help... and Satchel mistook the voice coming out of the walls for God. Hilarity Ensues.
 * Reed Richards of the Fantastic Four does this now and again as well. Justified in that his powers are to stretch his body to any length, and width.
 * Scarecrow escaped out of Arkham Asylum this way. Justified in that this villain has always been a skinny britches. And it's Arkham Asylum.
 * Used again in the 1980s Frank Miller envisioning of Batman. True, this time it was an arranged 'escape'-with both Batman and Commissioner Gordon in on the act of breaking a villain out of an ORDINARY holding cell. However, this time the prisoner is the hulking Mutant leader, a man built enough to take on Batman in hand to hand combat. (The breakout was so that Batman could have a rematch, after also arranging for the entire Mutant gang to be on hand to watch their leader get taught a lesson in messing with the Batman.)
 * Ms. Tree makes an Air Vent Passageway escape as part of her Die Hard on an X plot in the "New Year's Evil" story.
 * In Dreamkeepers, Namah and Mace (And Whip) are both partial to this trope.
 * In Mickey Mouse and the Chirikawa Necklace, Mickey and Atomo Bleep-Bleep escape a deathtrap through an air vent. May be justified in that they are very small, especially compared to the Dogfaces that inhabit the Elaborate Underground Base.

Fan Works

 * This is the method that Draco uses to get the Death Eaters into Hogwarts in A Very Potter Musical.
 * This chapter of a Kim Possible Fanfic has a nice Deconstruction of the trope when Ron, dropped into the real world, sneaks into a library through the airvents and naturally gets dirty while crawling through them. Then he starts to wonder why the vents in the supervillains' lairs were never less than spotless. Who was cleaning them? How? Why?
 * It's often a good idea to clean out ventilation systems to increase air-flow efficiency, reduce allergens, and stop a significant layer of dust accumulating on everything in the building every night. Particularly in warehouses with the giant ventilation systems that someone could actually crawl through.
 * Or there might simply be enough traffic in the ventilation system of the average villain lair to prevent dust gathering... Let's face it, those bases usually last a month or three, and see twenty-odd people getting around by air vents in that timeframe.
 * In another Kim Possible fanfic 'To Bebe or not to Bebe' Kim and Ron are captured by a surprisingly compotent villian who not oly has air vents to small to crawl through but also took all their equipment and destroyed it rathewr than leave it out to pick up when they escape.
 * A necessary reference to Nobody Dies: Terrifying!Rei's favorite method of Stealth Hi Bye is to drop out of NERV's any ventilation system. He~eeey. Oh Crap. Running now.
 * Later revealed to be a trait common to all Lilith-based Nephilem, as when . Kensuke is picking it up as well, due to his... "friendship" with Rei.
 * Used in the Portal 2 fanfic Test Of Humanity, though it's more of an "incineratior exhaust pipe escape". Subverted in that
 * In Fallout Equestria Pink Eyes, the main character Puppysmiles is just a little filly, meaning it's easier to crawl around in tight spaces. She uses this to enter a locked-down fortress to search for her mom.
 * Inverted in Calvin and Hobbes The Series: Andy and Sherman are captured by a possessed air vent.

Films -- Animation

 * Toy Story 2. Naturally, ducts are much more convenient when you're eight inches tall.
 * Lilo and Stitch: This is how Stitch escapes from the prisoner bay after breaking out of his cell. Justified because he's small and fast, and all the guards know he's there, they just couldn't shoot him in time.
 * In Sky Blue, Shua flees Ecoban through the air vents after going through the Absurdly Spacious Sewer system.
 * Subverted in Ed, Edd 'n' Eddy's "Big Picture Show". Taking refuge in Eddy's Brother's room, the Eds try to get out the window. It's bricked in, as shown in a previous episode. ("My brother's a whiz at laying bricks.") While Edd tries to find another way out, he trips over a rug, revealing a heating duct. Eddy quickly pries open the grate, jumps in, and... more bricks. Then Ed finds the "In Case Of Movie Break Glass" case.

Films -- Live-Action
"Smecker: Little assault guys, crawling through the vents, coming in through the ceiling -- that James Bond shit never happens in real life! Professionals don't do that!"
 * Used quite famously in Die Hard: the villains quickly realize the hero John is using the ventilation system, and come perilously close to catching him inside. Also lampshaded in that John McClane is rather muscular and the vents are small; he remarks, "Now I know what a TV dinner feels like."
 * Plus he gets really dirty.
 * In Masterminds, Ozzy has an extended sequence where he dodges the hostage-takers in air vents. Done realistically in that the school is huge but only covered by a small group, the ducts are barely large enough for him to fit in the first place, and he makes enough noise that they can follow him once they stumble upon his location.
 * Used, more realistically than usual, in Sky High. One character's power (glowing in the dark) comes in handy here, allowing the others to see. And only the character who can become a rodent can reach the place needed to save the day. Lame power? What's a lame power?
 * Subverted in The Breakfast Club. After John Bender is locked in a broom closet by Principal Vernon, he tries to escape through an air duct, which collapses just as he is muttering the punchline to an obscene joke to himself (and the audience, of course).
 * Minor subversion in Serenity, when the Captain must get a wrench and properly remove the duct cover before executing the trope to get past a locked door.
 * And played for laughs later on at the end, when Simon and Kaylee are taking the "unresolved" out of their UST. They begin removing their clothes, then start kissing, then they fall down out of sight... and the camera pans up to show River watching from an air duct overhead.
 * Ceiling Cling River is watching you procreate.
 * Subverted in The Fifth Element, where the villain sweeps the ceiling with a machine-gun, perforating Milla Jovovich, who is hiding in the ceiling duct.
 * Played straight earlier, when she escapes from the cloning lab by running through rather massive air ducts to get outside.
 * Subverted in The Boondock Saints, when the brothers break into Copley Plaza Hotel to assassinate Russian mobsters, but get lost and break the vent... granted, they happen to near-fall into the correct room. Agent Smecker than explains how this trope is only ever seen in "bad television":

"Servo: Diabolik's only two feet down the tower, moving as fast as he can..."
 * Played with in Mr. and Mrs. Smith, where assassin Jane Smith's place of work has security lasers everywhere to keep intruders out, including the vent system, as Mrs. Smith is the owner of the company and has used such tactics herself in the past.
 * Used in Tenacious D in The Pick of Destiny, complete with a rooftop airvent to enter through and enough lighting inside to see. The shaft does however break apart and fall through the ceiling once two people are inside it, crashing to the floor below and alerting the guards.
 * As evidenced in the fifth Halloween movie, Michael Myers does not take too kindly to this trope. He proceeds to relentlessly stab the outside of the air vent when a would-be victim (his niece) tries to escape through one.
 * In Alien, the monster actually uses the air duct escape against the protagonists, and then in Aliens Ripley and the marines use ducts to escape the monsters (which likewise use the ducts to invade).
 * It's only explained in the movie's extended director's cut, but the character of "Newt" earned that nickname because she was so good at playing hide-and-seek in those same ducts.
 * Played with when the Aliens in Aliens bypass the walls and doors by sneaking through the ceiling plenum à la The Breakfast Club as noted above, correctly using the structure to carry their weight and cross the the lay-in-ceiling. Of course this only serves to prove that that The Company shops out their work to the lowest bidder; it's common practice in cheap office space to span an entire suite with a single suspended ceiling and simply stop the walls when they hit the underside of the grid.
 * In Desperate Measures, the villain Peter McCabe is capable of taking an entire medical facility over by himself once he gets to the control room, able to lock and open doors at will and talk via the police intercoms to the movie's main character, Frank Connor. An agent attempts to listen into McCabe and Connor's conversation by situating himself in an air vent above the control room and lowering a small mic, but he is soon found out by McCabe. He shoots into the ceiling and waits until he sees blood drip from the bullet holes in the ceiling. When asked by Connor what happened, he simply replies "Just a rat, Frank. Just a rat."
 * In Mission Impossible, Tom Cruise's character infiltrates the CIA headquarters this way (along with Jean Reno), which leads to the famous "dangling in the ultra-secure white room" scene.
 * In Mission Impossible III, Ethan escapes IMF headquarters like this. Given they are the masters of the air vent entry, you would have thought they'd had better security, but no.
 * He didn't so much "escape" as "get into another office in the same building that shared the vent system".
 * The vent Ethan crawls out of is in a room with pamphlets for the Virginia Department Of Transportation, his cover job, implying that he uses that room frequently and either knows of - or set up - that opportunity, should he ever need it.
 * A variation happens in the Italian movie Diabolik (featured on the last episode of MST3K), where the title character scales up a castle wall using a pair of devices consisting of three hand-activated suction cups attached to a handle. Of course, Mike and the Bots have a field day with it.


 * Another Mystery Science Theater 3000 film, Future War, subverts this trope. A minor character climbs into a air vent to avoid a rampaging killer cyborg. The vent promptly collapses through the ceiling under the weight of her average-sized body and she gets killed.
 * Subverted in the James Bond film Goldeneye. The Dragon pursues Natalya Simonova into a breakroom and, seeing the air vent cover pulled down, opens fire into the air vent. After she's left, Natalya emerges from a cabinet, having used the air vent as a Decoy Hiding Place.
 * Double-subverted way back in the film Dr. No. When Bond tries to escape his cell through the vent, he gets electrocuted when he touches the grill. However, he tries again by using his shoe to push it out and succeeds in escaping. As a nice touch, he experimentally taps the grill at the other end with his feet to make sure it isn't electrified.
 * And, as noted in Irregular Webcomic, in the book, it was a deliberate obstacle course set up by Dr. No, complete with viewports for entertainment, so the red-hot surfaces and tidal wave of water serve a purpose. Other than, of course, to provide a wet, shirtless Sean Connery. Mmm... wet, shirtless Sean Connery...
 * Used and subverted in The Negotiator, where the SWAT team uses small vents for running fiber-optic cameras and larger vents for team members. When the title character barricades himself into an office, one of the precautions he takes is to close off the vents as best he can with available materials.
 * Later played straight in his attempt to escape the office building.
 * One of the scenes in I Now Pronounce You Chuck and Larry involves the main characters (who are firemen) having to rescue a would be thief that got stuck trying to sneak through an air duct.
 * In Santa Claus Conquers the Martians, the creepily jolly St. Nick and some Earthling kids escape from a spaceship's air lock through the ventilation duct -- employing Santa's long-established ability to fit through chimneys.
 * Mystery Science Theater 3000 adds an appropriately Bondian line "So, Mister Claus, you have a nasty habit of surviving!"
 * Sneakers. One of the team infiltrates an enemy-controlled building through the ventilation system, and tries to get out the same way after the job is completed.
 * Subverted and lampshade hung in Harold and Kumar Go to White Castle, when Kumar calls in an incident as a diversion and crawls through a heating duct to get Harold out of jail, making a racket, having an argument with Harold (who doesn't want to escape) while still in the duct, getting stuck in it and eventually causing the duct to collapse, falling onto a table and hitting his head on a file cabinet. He does manage to grab the bag of weed and get Harold out due to lampshade-hung Police Brutality, though.
 * Referenced in 12 Monkeys when the staff of a mental hospital find Cole has vanished from his restraints, in a locked room. Their eyes turn to the tiny airvent way up on the high ceiling. After all, there's no other way out. Unless he was snatched through time....
 * Slightly altered in Crossfire, where the main characters are able to escape an army of policy by crawling through an air duct of a building.
 * Parodied in Top Secret. While incarcerated in Flugendorf Prison, Nick Rivers tries to escape through the air vent system. He ends up sticking his head out of a medicine cabinet and a toilet before finally sliding back out through the vent into the cell.
 * The Resident Evil films:
 * Resident Evil. After leaving the Red Queen's chamber the 2nd time, at one point the surviving team members go through air vents to evade the zombies.
 * In Resident Evil Apocalypse, Alice escapes Nemesis via a random spacious disposal chute.
 * In Resident Evil Extinction, one of the Alice clones jumps into an air vent to escape a replica of the Laser Grid deathtrap from the first movie. Milla Jovovich ends up in Air Vents a lot, as noted by The Fifth Element examples above.
 * In Men in Black II, the worms get to the power control of MIB headquarters through the air vents.
 * Daylight has Sylvester Stallone get into a caved-in tunnel through a air vent. Since the air vent was meant to supply air to an entire car tunnel, its huge size is justified. However, the architecture of the system is still not completely realistic.
 * In Paul Blart: Mall Cop Blart attempts to use an air duct to escape from some Mooks but only ends up completely giving away his position by all the noise and all the dents showing up, leaving him open to attack. In the end the air vent just breaks loose anyway, proving to not be a stable place to climb in in the first place.
 * In D.E.B.S., Lucy Diamond uses the air vents to infiltrate the building in which Endgame is occurring, but it turns out that Homeland Security has been briefed about the possibility that spies could enter illegally through such routes.
 * The famous trash compactor scene from Star Wars, which is a subversion because in that case, attempting to escape led to an even worse situation.
 * Yoda's escape through the vents in Revenge of the Sith. Justified, of course, by Yoda's small size.
 * The 1998 American Godzilla movie has this, where Audrey Timmonds and Animal Palotti are sneaking through the vents of Madison Square Gardens in order to escape Godzilla's babies. Also subverted in the movie, since it turns out the vent can't hold their weight after all.
 * In The Brothers Bloom, Penelope tries to escape from the police using a ventilation duct.
 * Rather a subversion, as the air duct is not soundproof, and she barely gets a room away before it collapses, dropping her right into the room with the well-armed police squad.
 * In Winning London, Riley and Brian help the hostages escape using the air vents.
 * In 1408, protagonist Mike Enslin attempts to escape from the titular room by crawling through the air duct...only to discover that one of the room's many long-dead occupants has taken up residence there as well. He manages to escape the ghoul by quickly backtracking out of the vents, but the attempted escape in the first place didn't do anything, as most of the airvents leading to different rooms simply lead to various memories he's had throughout life, making it a pointless effort to begin with, not that he knew that until he tried.
 * 28 Weeks Later has Andy using this to escape a room in which the ranks of the infected are growing exponentially.
 * Subverted in the Day of the Dead remake, as one of the zombies catches the heroes trying this and actually follows them into the vent.
 * Subverted in the B-movie Chopping Mall. The teens attempt to escape the shopping mall's malfunctioning killer robots through the airvent. Only the girls get in before the guys are forced to flee for their lives. The girl end up abandoning this plan when it seems the computer has turned on the heat, forcing them to leave the vent and re-enter the mall.
 * Done in the Lorenzo Lama vehicle Snake Eater II: The Drug Buster: as Lama's character wiggles his denim-clad gluteal region through the mental asylum's air duct, he meets two characters going in -- a hired woman, and a pizza delivery guy!
 * Inception had the group breaking into an ice fortress using a air vent system. Justified since they had created those air vents to be big enough to let people move around.
 * The famous The Shawshank Redemption escape although instead of an air vent, it's a sewage pipe.
 * In Toy Soldiers, the main characters use the air vents to get from the bathroom to the headmaster's office.
 * The cast of The Pool try to do this, but the killer will have none of that nonsense.
 * Played with in Eight Legged Freaks, when a character narrowly escapes the giant spiders by diving into a rooftop air duct into a mall's ventilation shafts ... only to slide helplessly down a slanted vent, then get trapped when the grill at the bottom won't come loose.
 * In The Journey of Natty Gann, Natty escapes from a reform school via some kind of vent which she gets into by removing a grate from the bottom of the bathroom wall.
 * Used as a means of navigation in the remake of The Poseidon Adventure. Handled a bit more realistically than most examples of this trope; the ducts are wide enough to crawl through without very much effort, but one character does get stuck in a compressed section and has to be helped out, another one suffers from claustrophobia, and the heroes nearly drown due to the rising water because it takes a lot of effort to get the panel on the other side open.
 * Also used in the sequel to the original movie, Beyond the Poseidon Adventure, complete with internal lighting fixtures.
 * Memorably parodied in The Brothers Bloom. Penelope needs to smuggle a MacGuffin out of a church while the police are thoroughly distracted. She fits in the air vents well enough, but they are not concealed in the least, and the clamor she makes attracts the police to her. The duct has very little support, so it breaks open right in front of an entire SWAT team, and she picks herself up into a Fighting Stance.

Literature
""I saw a film where there was an alien crawling around inside a spaceship's air ducts and it could come out wherever it liked," said Johnny reproachfully. "Doubtless it had a map," said the Captain."
 * The small kids who live in Northberg Educational Facility discover that they can go anywhere they want in the air vents. And the child-sized "secret" areas they lead to.
 * James Bond escapes confinement in Dr. No through some ductwork, but he soon discovers that it was a purposefully-built series of hazardous obstacles (poisonous spiders, extreme heat, etc.) intended as a Death Trap. It's not explained that it's a Death Trap in The Movie, though, so it doesn't really make sense.
 * That's because it wasn't a Death Course in the movie, just a shaft guarded by a Booby Trap that Bond is able to bypass.
 * Justified in the sci-fi book Footfall, as the aliens are twice human size and deliberately put the captured humans to work cleaning the spacecraft's air ducts. Their prison cell also doesn't contain a handy air duct, forcing them to escape before using the ducts to evade.
 * In Illegal Aliens by Nick Pollotta and Phil Foglio, abducted humans on an alien ship hide in the air vents, because all the movies say that's what you do in that situation -- only they aren't air vents; they're conduits for a horrifically deadly gas weapon, which the aliens are preparing to flood throughout the ship, because they can't locate the humans....
 * Something similar to the above happens in Artemis Fowl: The Arctic Incident. Artemis has to crawl through a duct filled with fuel for the building's plasma weapons. Before his helmet runs out of air. Without being able to see where he's going. Knowing full well that if anyone turns on the plasma cannons, he's literally toast. Not to mention that once he gets out, he has to be sprayed with anti-radiation foam or he'll likely develop cancer.
 * Subverted in Christopher Brookmyre's One Fine Day in the Middle of the Night. After an earlier discussion after action movie tropes, one of the heroes spots the "Holy Grille" as the way out when they're held hostage. Unfortunately, he didn't reckon on the fact that crawling through metal ductwork is incredibly noisy, so everyone hears him as he tries to squeeze through.
 * Justified in Enders Shadow. Bean uses the air ducts to explore and reconnoiter, but he can only do it because he designed a specialized workout to develop the muscles he needs to pull himself through at odd angles, and because he's really, ridiculously small. Eventually he grows too big to use the vents anymore.
 * He also, later on, uses the bigger vents in the commander's room to trap Achilles and force him to surrender.
 * Works better in Mrs. Frisby and the Rats of NIMH than in most stories due to the escapees being rats.
 * Well, right up until the system starts ventilating. This is one of the scenes that, legend has it, convinced Disney to pass it by as an animated adaptation. Something about having a large part of the party wiped out faster than the Redshirt Army, and without even an enemy to credit for it. They also need help in opening the grilles, too.
 * Parodied in The Adventures of Samurai Cat, in which a cruise ship's air vents "... appear to have been designed for covert transportation." -- "That would explain the moving walkways and vending machines."
 * Lyra crawls around in the dropped ceiling in Bolvangar in Philip Pullman's Northern Lights. Being a twelve-year-old girl, she's smaller and lighter than most Action Heroes, but she gets caught anyway, and almost transformed into a soulless abomination. She's only saved because the Big Bad had a special interest in her, and was present.
 * Used in the Honor Harrington spinoff Crown of Slaves, but half-subverted by the simple expedient of using it realistically. Crawling around in them is murderously hard work, characters without detailed schematics get badly lost, and it proves almost impossible to remove a grille without the proper tools.
 * Additionally the ducts in question are on a space station and are deliberately designed to be large enough to crawl through since they double as maintenance access passages.
 * Referenced in Terry Pratchett's Only You Can Save Mankind:

""He was really upset when we fished him out!""
 * He also pokes fun at it in Going Postal when, after a character fails to tunnel out of his jail cell, a guard remarks that the last guy in that cell - who happened to be unusually small and nimble - managed to squeeze through a tiny drain in the floor. Unfortunately, it didn't lead to the river like he thought.


 * In John C. Wright's , Vanity finds an accessible air vent. On the other hand, she has an ability to find secret passageways that weren't there before she looked.
 * In Sandy Mitchell's Ciaphas Cain novel, Cain's Last Stand, the air vents are exactly the place genestealers like to hide.
 * Used in the last two books of Timothy Zahn's Dragonback series; the (less-than-subtle) justification is that large air vents are actually standard design in capital ships, so that in the event of a hull breach emergency air supplies can be funneled to the compromised areas in large amounts, buying the occupants time to reach emergency air masks and so on.
 * Although humans can't fit through them as it is so I'd almost call it a lampshading.
 * Slightly altered in Harry Potter and The Chamber of Secrets, using the castle sewer-pipes for the monster to invade from -- and for the heroes to find -- the title chamber.
 * Hogwarts Castle has got to have the most gigantic pipes ever seen... particularly for being built by wizards.
 * My impression was that only one pipe was built that way -- a basilisk, such as Slytherin's monster, can't get through a normal drain pipe to get to Myrtle's bathroom, hence the bigger one under the sinks. The other pipes would be normal.
 * Since one of the school's founders built the chamber, I always figured he had insider knowledge, or convinced the others it was a good idea, or just cast a spell on the basilisk because he was really powerful.
 * Comes up in several variations (breaking in, breaking out, air ducts, hanging ceilings...) in places in the Vorkosigan Saga by Lois McMaster Bujold, particularly the short story "Labyrinth" -- where it involves problems like ducts forking or being blocked by grilles, and the others being only passable by the rather less than five-foot-tall main character, not his companions.
 * In Graham McNeill's Warhammer 40000 novel Storm of Iron, this is how Hawke escapes a launching rocket and a Chaos Space Marine.
 * In the Women of the Otherworld short story "Chaotic" in the anthology Dates From Hell, Hope flees from a werewolf into an office, and finds herself in a dead end. She tries to escape through the air ducts, but she makes too much noise when moving and has to freeze when the werewolf enters the room. He finds her immediately. Later, after the pair has teamed up, they both move around through the air ducts, which are noisy, painful, cramped, and dusty. Still later, the bad guy enters a room looking for Hope, and while he's investigating the unscrewed air vent the good guys come out of their real hiding places and get the jump on him.
 * Averted in Robert A. Heinlein's Red Planet when one of the good guys proposes taking a vent grille off of a wall to get to the room on the other side. His friend points out that there will certainly be a similar grille on the other side, fastened by screws they won't be able to reach.
 * In Lucky Starr and the Oceans of Venus, Bigman Jones sneaks through the air ducts in order to prevent a psychically-controlled man from opening the gates and flooding the Underwater City. The Venusian leader points out that air ducts "aren't as big as all that," but the trope is slightly Justified Trope because, as Bigman painfully replies, "I'm not as big as all that, either."
 * Deconstructed in Black Dogs. The ventilation in question is portrayed as tough, claustrophobic going in the dark, with Lyra, the protagonist, suffering several minor injuries, and a high chance of her falling and breaking her neck. Or breaking something else that renders her unable to escape, and dying slowly over several days.
 * Subverted in the final book of the Sten Series, by having the hero nearly get stuck in a claustrophobic moment.
 * Both played straight and subverted in John Ringo's Choosers Of The Slain. They need to sneak into the secure facility of one of the bad guys, so (played straight) they pick the slimmest girl on the team, as the men on the team are too large especially wearing all their weapons. Subverted because they knew she would get stuck half-way down when the air vents narrowed, so her sole job was to get to that point and release a small robot (an R2-D2 toy they had picked up in a toy store and then modified to include surveillance and communications gear) which could go the rest of the way.
 * Used by Cammie and Macey in the third book of The Gallagher Girls series to get back into a building, though in this case it was still for escape rather than infiltration.
 * Hilariously subverted and lampshaded in Star Trek: Section 31: Abyss. After escaping her cell, Ezri Dax goes up into an air vent, which (contrary to what the holonovels of her youth would have her believe) is very dirty, dark, small and has creepy things living in it. (She is, however, successful in using the air vents to move throughout the base to important rooms).
 * Subverted in To Aru Majutsu no Index. In Volume 17 of the novels, Touma asks if he could use the ventilation ducts in the plane, but the flight attendant says that the ducts are too small. Instead, Touma asks for some hot tea and coffee to pour down the duct, causing thermal expansion and make the terrorist on the other side think that there's someone crawling through the ducts. As a result, the terrorist on the other side gets some boiling hot tea to the face when he checks the ducts.
 * Used in Age of Fire, where the two dragon siblings escape from a raid on their home cave by escaping through naturally formed air passageways.
 * In short story "In the Bone", the protagonist uses air ducts which were too small for his alien opponent but nonetheless navigable by the smaller human form. It's noted that some of the ducts are indeed too small for the human.

Live Action TV
"Evelyn: There must be some other way. An inspection hatch, or even, God help us, a ventilation shaft!"
 * The A-Team: Several episodes, including one where Murdock escapes from a locked room, with his hands bound no less, through a ventilation shaft. Hannibal and B.A. boost him into the shaft while Face distracts the guard.
 * Buffy the Vampire Slayer and Xander use this method to escape from vamp Jesse and his new friends in the electrical tunnels in "The Harvest".
 * In "Out of Mind, Out of Sight", Marcie Ross lives above the school's music room in a space accessible only by climbing up through the drop ceiling.
 * In the episode "School Hard" Buffy gets out of a locked classroom and gets the drop on Spike by crawling though the space above the drop ceiling (she is at least shown traversing a wooden catwalk).
 * Also worth noting, Spike notices, and in a singsong voice says “some-one's-in-the-cei-ling”.
 * Subverted in "Gingerbread", where Xander and Oz can fit into the vents but become lost and only reach the rest of the cast after the monster of the week is already dead. "We're here to rescue you..."
 * Twenty Four enjoys playing around with this. Sometimes played straight and other times, the villains are quick to seal them to prevent the cliche from happening. One notorious use of air ducts was seen in a fifth season episode, as agent Jack Bauer uses duct tape to seal a shaft and prevent nerve gas from seeping into a safe room.
 * Star Trek has the "Jefferies Tube" tunnels criss-crossing the ship and was actually designed for human access, but is quite often used in this way.
 * Dr. Helen Noel saved the day this way in Star Trek the Original Series, episode "Dagger of the Mind".
 * In "The Trouble With Tribbles" Scotty speculates that the tribbles got into the food processors on the Enterprise via the actual air vents. Spock realizes that the grain the Enterprise is guarding on the near-by space station is in storage compartments with similar vents, prompting Kirk to beam over and leading to the episode's Crowning Moment of Funny.
 * Star Trek the Next Generation had a few Die Hard on an X episodes where the Jefferies Tubes come in handy this way.
 * Star Trek Enterprise. The ship is taken over and everyone is locked in their rooms. Hoshi, being the smallest person on board (and of course, a regular) manages to wriggle out through the vents. Presumably, Hoshi is the one called upon when something in the vent needs fixing.
 * Or she was chosen so we could have a gratuitous Fan Service moment where her shirt gets pulled off. Especially since the ducts didn't seem that narrow anyway.
 * If anything, that was at least acknowledging that the Jefferies Tubes would be guarded by the bad guys. That vent existed solely during construction and was closed off upon completion, it was never intended for people to pass through.
 * In an episode of Stargate Atlantis, Zelenka crawls through a vent to turn the city's power back on, although in this case the air vents are the same size as you'd find in the real world so he did have a very hard time moving around. In Stargate SG-1, the aforementioned team uses this trope every time they're on a Goa'uld mothership.
 * Subverted on Undeclared, where Steven, finding himself trapped in a room, attempts to crawl through an external ventilation duct, which breaks from the wall and falls as soon as he enters.
 * Justified in The X-Files episodes "Squeeze" and "Tooms", since the killer -- Eugene Victor Tooms -- is a mutant whose power is to be capable of squeezing through tiny openings.
 * Used with absolutely no justification in "Ghost in the Machine". Though there is a slight subversion when Scully learns firsthand the downside of trying to climb through the airducts when an insane AI controls the ventilation system...
 * A conspiracy theorist trying to spy on a defense contractor's meeting in "Three of a Kind" gets caught when the duct audibly flexes under his weight.
 * Unnatural History subverts this hysterically. Jasper tries to think of a creative way out of the room he's trapped in, and the camera focuses on a air vent duct. The next shot show him struggling futilely to pry the vent free.
 * In the second season of Lost, this was a legitimate way of getting around in the Swan station. Kate used the ventilation ducts to escape imprisonment in the food storage room in the episodes "Adrift" and "Orientation", and in the episode "Lockdown", Ben (then going by the alias of "Henry Gale") could escape from being locked inside by blast doors.
 * Locke later sealed the vents to put an end to this kind of thing, which didn't work out so well later once he and Jack found themselves locked inside.
 * Lampshade Hanging in the Doctor Who episode "The Satan Pit"; when Rose suggests escaping through the maintenance ducts, Security Officer Jefferson replies "I appreciate the reference but there's no ventilation. No air, in fact, at all. They were designed for machines, not life forms." They're able to escape through them anyway, though, by manipulating the air-pressure controls to "flood" certain ducts.
 * According to Doctor Who Confidential, the reason Jefferson says he appreciates the reference is because the actor playing him was actually in one of the Alien films -- Danny Webb was in Alien 3.
 * Lampshaded again in the Big Finish Doctor Who audio adventure The Apocalypse Element.

"The Doctor: If you're supposed to be the superior race of the universe, why don't you try climbing after us? Bye bye!"
 * Used straight in "The Ark in Space" (realistically: Sarah Jane Smith is the only one small enough to fit and even she get stuck) and "The Tenth Planet" (hilariously: Ben has a map, albeit one drawn by the man who designed the ventilation system). Also played straight in the Third Doctor episode, "Invasion of the Dinosaurs", where Sarah Jane is locked in a closet and escapes through an air duct.
 * Beefy science teacher Ian Chesterton uses one in "The Aztecs" while the First Doctor makes time with a local lady.
 * Used by the Fourth Doctor and company in Tom Baker's second Dalek story "Destiny of the Daleks" -- notable for the Doctor pausing to mock the Daleks' inability to follow them...

"The Doctor: I love 1958, no one's seen Die Hard. Or Alien. Or Die Hard 2, or Aliens, or Die Hard 3..."
 * The Doctor and companions use one of these to escape from Area 51 in the animated special Dreamland. The Doctor lampshades their captor's Justified Genre Blindness.

": Ventilation shafts, that takes me back. And forward."
 * The frequent use of this trope in its parent show is lampshaded in The Sarah Jane Adventures episode "Death of the Doctor".

"Adam: Why, Thor, the God of Thunder, is trying to enter my building! Tory: Somebody needs to check that air conditioner!"
 * The Cybermen's Cybermat devices could infiltrate target installations by going through ventilation ducts.
 * The Suite Life of Zack and Cody: Zack and Cody easily spend more time traversing the Tipton's air vents than just using the hallways and doors. So far, Max and Zack are Genre Savvy to the air vent appeal.
 * Ned's Declassified School Survival Guide: Many A Simple Plan requires use of the school's elaborate, labyrinthine air ducts, which eventually gave out in the Grand Finale.
 * Spoofed on Arrested Development: in one episode, George Sr. finds an entrance to the air ducts behind the refrigerator and attempts to escape house arrest. Not only does he fail to find a way out of the house, Buster pushes the refrigerator back into place and traps him inside.
 * The master of air duct navigation is clearly the Mission Impossible jack-of-all-trades Barney Collier. And one of the few times he wasn't doing it, he was coaching the woman who was.
 * Somewhat justified and subverted in some episodes, particularly early ones. In one they had to employ a contortionist (played by Eartha Kitt): only she was small and limber enough to crawl through the ducts, and they even gave her a Cool Tool so she could unfasten, from inside the duct, the screws that hold the grille on from the outside. At other times they sent a miniature remote controlled hovercraft and even a small trained dog through vent ducts and similar. But most of the time, yeah.
 * Justified in Farscape where the diminutive Rigel often uses air ducts and service tunnels to travel when the ship is being invaded or he's feeling particularly paranoid.
 * My Name Is Earl: Earl engineers a jail break using this method. Unfortunately, the duct collapses in the warden's office.
 * The unaired pilot I-Man subverts and Lampshades this one: Scott Bakula references it as an escape plan... and then finds out that the room only has a regular air vent.
 * Myth Busters tested this trick along with a variety of other cat-burglar techniques. Jamie used the common technique of using powerful hand-held magnets to climb the vertical shaft, only to cause a thunderous sound as they connected to the vent walls, defying the point of it being a "stealth" technique. Adam, on the other hand, used vacuum "cups" on his hands and feet that would grip the vent. Though it wasn't nearly as noisy, it was far from silent, and the equipment lacked reliability (breaking down several times during the course of the show) and it was tricky to use. Adam himself said that he wouldn't trust his life to such machinery.

"Joel: You know, it's funny how movie directors always make air vents big enough to crawl around in."
 * The Australian series Escape From Jupiter features a moonbase and space station/makeshift rocket that both feature large air ducts. Of course, they're also likely some sort of Jefferies tubes -- just built in case of need for extended residence.
 * Famously Lampshaded in Mystery Science Theater 3000:

"Wendy: We're coming from an isolation chamber in a secret headquarters built by an organization so covert we don't even know who they are, yet somehow we have vents large enough to crawl through, with accessible registers everywhere. Was this building designed by TV writers or what?"
 * Lampshaded and subverted in an episode of Burn Notice. When trapped in an office building, Michael wryly notes that air vents are viable escape routes... if you happen to be size of a four year old. He does state, however, that instead of using air ducts, you can instead use the sub-ceiling of an office building to escape danger.
 * His mother remembers he crawled through an air vent so he can go to the theatre and watch Star Wars.
 * Justified in a later episode (and spelled out in the narrative) that they were in a medical experimentation lab and the ventilation system had to be sufficiently large to facilitate a quick full air turn around in the event that something bad happened allowing him to climb to a higher floor in the building (in the narrative he says that normally it's not possible to use the airvents due to their size and lack of strength as well) (the system ventilated through the roof, he cut through it to get onto the second floor).
 * Lampshaded and subverted in the Middleman episode "The Clotharian Contamination Protocol":

"George: (on phone) Hello Margery, George Costanza. How are you sweetheart? Listen, can you give Mr. Thomassoulo a message for me? …Yes. If he needs me, tell him I’M IN MY OFFICE! Thanks."
 * The subversion being that normally the vents are only a few inches in diameter, but they expand during an alert for this exact purpose.
 * The Middleman explains that the "Nakatomi Protocol" specifically enlarges the vents and turns off the surveillance.
 * Hiro and Ando attempt one on Heroes, but their captors show up at the cell before they make it into the vent.
 * Not "escaping" anything, but the "steam tunnel spelunkers" aspect shows up on Numb3rs, when it is revealed that Larry had been living in the tunnels on campus for awhile.
 * On the Friends episode "The One With the Birth", Phoebe, Susan and Ross get locked in a janitor's closet in the hospital. Phoebe tries to escape through the vent but gets stuck, while Susan and Ross just get let out by the janitor.
 * Lampshaded in Dark Season episode 5 where Marcie escapes and says, "A ventilation shaft. Marvellous, I'm a cliche."
 * In the Red Dwarf episode "Duct Soup", the crew spend most of the episode crawling around the ship's exceptionally large heating ducts to fix the thermostat. This, unfortunately for them, includes a badly claustrophobic Lister and the ducts being washed down and then air-dried...
 * The air duct was used to get Robin Hood out of a Norman castle in the TV series The New Adventures of Robin Hood. The series was a bit on a Hercules: The Legendary Journeys and Xena level of authenticity but (sadly) not meant as a spoof.
 * The old Voyage to the Bottom of the Sea series was rife with this trope, especially in the later seasons, when it seemed every third episode had a villain or Monster of the Week or regular character evading a villain or MotW getting into the ventilation system at some point. Played straight for the most part, although somewhat subverted in that the ducts themselves were quite roomy, and the vents were about a yard square or more in size, hinged like a door with a latch that anything brighter than a rock could operate, allowing convenient access.
 * Battlestar Galactica Reimagined, "Blood on the Scales". Chief Tyrol spends most of The Mutiny crawling through shafts to get to the FTL drive. Unlike some examples of this trope, these are shown to be narrow, unpleasant (especially when going past the urinals), and bloody tiring to crawl through -- when Tyrol is caught at one stage, he invites his captor to shoot him then and there as he's too exhausted to clamber out and be taken prisoner.
 * Lampshaded on Leverage: "Looks like Parker's going to have to climb through the air duct again..." Somewhat justified in that Parker is a) a master thief with an extensive knowledge of building layouts, and b) petite.
 * Played with in one season three episode, when Parker encounters difficulties trying to do this as there are lasers blocking her path. Why it wouldn't be cheaper to simply make the ducts too small to crawl through is never addressed.
 * Used on Primeval when Abby and Connor needed to get to a certain floor in a skyscraper. Since taking the stairs/lift would have been incredibly dangerous (there was fog coming out of an anomaly that obscured the floor, and moving in the fog were giant worm things that were hard to see), they had to use the air vents.
 * In one episode of Las Vegas, some bad guys take over the Montecito security centre. Danny McCoy uses the airvent system to try and get some intelligence on them. Right after the audience starts wondering why the hotel with "the best security on the strip" has such a gaping security hole, the vent collapses, conspicuously dumping Danny in the middle of Security. On his own desk, I believe. Given that his predecessor, Ed Deline, had a bit of a mischievous streak, it's entirely possible he rigged the whole thing up.
 * This is used on several episodes of the first season of The Pretender. During the first season finale Jared does this to break into and escape the Centre.
 * On Smallville, Clark travels through the Luthor Corp air ducts when he is Brought Down to Normal. In a later episode, this is also part of Jimmy's spy tactics.
 * In the HBO Movie Deadly Voyage (depicting the murder of 8 African stowaways on a Europe-bound cargo ship), the 9th stowaway manages to to escape from the ship and his would-be killers by shimmying up one of these. Made all the more harrowing by the fact that movie is based on a true story and that this isn't Adaption Displacement--this is EXACTLY how the man was able to get away.
 * Along with many, many other tropes, this one is parodied in Spaced when Mike and Tim are trying to escape from the offices of Dark Star comics: "Ah, the air vent. Simple, classic."
 * In Chuck, there was once an incredibly roomy network of air vents, with lights.
 * Roomy air vents were used in at least one episode of I Spy, one of the more 'realistic' 1960s spy shows.
 * Contra Security of Breaking In has large roomy air ducts... with booby traps. Knowing Oz, he may have had them built that large just to trap intruders inside.
 * In an episode of Law and Order SVU, Elliot hides inside an air vent in order to spy on someone.
 * Seinfeld, when George uses an air vent to break into his office after his boss tries to get him to resign by barricading it.


 * In The Secret World of Alex Mack, the eponymous heroine did this a few times, and at least once escaped captivity via the plumbing. It helped that she could turn into a liquid.
 * In Lois & Clark: The New Adventures of Superman's Die Hard on an X episode "Fly Hard", Jimmy Olsen manages to escape unseen into the air vent system when terrorists initially take over the Daily Planet. Once he exits the system, however, it doesn't take long before he's found and neutralized.
 * 1960's Batman episode "A Riddle A Day Keeps The Riddler Away". Batman and Robin use air ducts to infiltrate a building where the Riddler is holding a kidnapped king hostage.
 * Still shows up regularly in Supernatural, with Sam and Dean playing Rock-Paper-Scissors to see who'll go down in the ductwork. (It's always Dean. Dean is really bad at Rock-Paper-Scissors.)
 * Alcatraz: Rebecca uses a air vent to sneak into a bank during a hostage situation in "Cal Sweeney".
 * Done by the entire main cast in Pixelface when the zombies from Claireparker's game invade the console.

Newspaper Comics

 * In a Dilbert strip, Alice tells naive intern Asok "You must climb through the Jeffries tubes to reach the furnace before it fries us all!" He gets stuck half-way in, but that was her plan: "Today, Asok learns that life is not like Star Trek."
 * With Asok's lower body handing out of the vent, Alice puts up a sign that reads "Spank the Intern $.50"

Tabletop RPG

 * Dune: Chronicles of the Imperium main rules, adventure "Instrument of Kanly". The agents of House D'murjzin enter and exit the 35th floor of the Adici Enterprises corporate headquarters through an air vent.
 * FASA's Classic Traveller supplement Action Aboard: Adventures on the King Richard. An entire paragraph details how the air ducts can be used to move around the ship.

Video Games

 * Battlefield 2142 The Titans have vents on the top that provide an alternate way to enter, however, unless the other team if full of idiots, they are usually boobytraped or being guarded by someone armed usually with a shotgun or a LMG.
 * Final Fantasy VII in numerous places, most notably in Shinra tower when the player eavesdrops on the evil corporate meeting from a ventilation duct connecting to a bathroom.
 * Chrono Trigger, and initially without weapons, as a Fake Difficulty. This can be avoided by putting Ayla in your party, as she fights with her bare fists. The other two in your party, however, will just watch and not even try to help, even if they know powerful magic, or are a metal killing machine.
 * Frequent in the Metal Gear series.
 * In Metal Gear 2, said vents are occasionally guarded by the memetically infamous Poisonous Zanzibar Hamsters.
 * One of the first areas in Metal Gear Solid has an otherwise level air duct with a lowered section in it. Said lowered section is flooded, which would render the duct useless for ventilation. Perhaps justified given the Shadow Moses base shows many signs of poor maintenance.
 * Very blatant in Portable Ops, which opens up with Snake escaping from a prison by crawling through the air vents.
 * The Chronicles Of Riddick: Escape From Butcher Bay, in which the ducts were used so widely they actually had directions scribbled inside them. Assault On Dark Athena continues this.
 * Grandia had this, including a side-trip to the women's locker-room...
 * Duke Nukem 3D did this so often that there is a small monster almost designed to be placed in the vents. In the expansion pack, the game has a nod to the famous air vent scene in the first Mission Impossible movie.
 * Lampshaded in Half-Life 2: Episode 1 by mentioning that Freeman used to participate in races to break into Dr. Kleiner's office when he locked his keys inside. Naturally, the air vents are now full of headcrabs.
 * And subverted in the same game, where one vent you crawl through collapses, landing in a room filled with Exploding Barrels and laser-tripwire mines.
 * Slightly subverted in Half-Life. At one point, the character is forced to crawl through an airvent. In a scripted scene, soldiers below hear the player, yell "He's in the ventilation system!" and shoot into the air duct, causing it to collapse. Whether or not you're in it is a matter of timing. In another instance, the guards hear you and toss a satchel charge in for an Outrun the Fireball sequence. Note that some of Half-Life's vents have ladders in them, suggesting that they may have been designed to allow people to go through them.
 * It is probably worth mentioning that Mr. Freeman crawls through the vents wearing what is basically a high-tech suit of platemail. But considering how deep the Black Mesa facility stretches, perhaps it is not quite unrealistic that it would use people-sized vents.
 * Deus Ex often includes alternate paths through air vents, which usually double as maintenance tunnels, complete with ladders and hinged grates. One of the NPCs even explicitly suggests it as a stealth route in the first mission, saying that "these 20th century buildings always have ventilation shafts". However, unlike Duke Nukem, there's also always a straight way.
 * BioShock (series) does this too.
 * And so does System Shock. The second game almost starts with one, and the first game had whole maintenance tunnels in addition to vents.
 * Mildly subverted in Deus Ex Invisible War; all the vents are comfortably navigable, but inevitably are patrolled by small, spider-like security bots armed with electrical shock-based weapons. According to characters, the bots are to combat any vermin that might enter the vents.
 * And just because it was such a big part of the first game, in Deus Ex Human Revolution, air vents abound, often leading to rooms with a couple of neat little bonuses, or an easy way around the guards. This is even lampshaded in an early conversation, where someone asks if the reason you took so long getting to his office is if you got stuck in an air duct.
 * Secret of Evermore had an escape through the ventilation system take up an entire dungeon. Fortunately, to make up for the confusion of navigating the vents, the game followed the trope pretty well by having no enemies inside them.
 * Golden Eye 1997 began one level with the player infiltrating a Russian base via the air vents.
 * Which reappeared in Perfect Dark. Gunfire in toilets. Always classy.
 * F.E.A.R. requires you to travel through air ducts several times per level in order to advance deeper into the facilities you're penetrating, whose covers are quite easily bashed in. Strangely, despite the game's horror atmosphere and the obvious darkness and claustrophobia factors, you are never once subjected to any sort of scare sequence within one.
 * Except one. During one particular part, you turn the corner, and Alma does the spider-crawl towards you -- before vanishing a foot away from you.
 * Alma seems to use this, popping out of an air vent right in front of you on one occasion. While you're utterly defenseless. On a ladder.
 * Played straight in Resistance Fall of Man when Parker uses a vent that pops open to escape from the conversion center, leaving Hale to find his own way out.
 * Apparently, design standards in the Metroid universe include a provision that all facilities and spacecraft must have access tunnels, air shafts, or other openings big enough for Samus Aran's Morph Ball form. (Expanded and partially subverted in Zero Mission, wherein after losing her armor, Samus must negotiate said tunnels on her hands and knees, which is dead slow, and Space Pirates can also use the tunnels, largely negating their escape value.)
 * More accurately, it seems all maintenance robots (which use the tunnels) are the same size as the morphball.
 * Aliens Versus Predator 2 (the game, not the movie) featured liberal amounts of duct crawling. The first few levels of the Marine campaign required constant duct crawling, including a situation where Frosty has to jump into a duct vent that a Xenomorph recently launched out of in order to avoid being eaten. The Alien campaign, however, was almost entirely composed of duct jumping for most of the early half of the game.
 * Though technically not an air vent, one mission in Call of Duty 2 involves a group of Russian soldiers infiltrating a German-held railway station via a long, damaged fuel pipe. The Germans are quick to catch on, though, and if he player isn't careful he can get caught by gunfire or hand grenades.
 * Paper Mario: The Thousand-Year Door has Mario go through air ducts twice in the course of plot in order to eavesdrop. He may also go through a third in order to gain an item.
 * One level of 24: The Game has Kim Bauer, armed only with a taser, having to crawl through ducts to get around a room full of bad guys. She has to move very slowly, though, or they'll hear her and shoot.
 * The titular character of the Sly Cooper series can do this in all his games. He usually does to break into places.
 * The only reason the title character's client in the third case of Apollo Justice Ace Attorney is accused of the murder is that it's a Locked Room Mystery and he's the only one small enough to fit through the vents (where they found his fingerprints). He did escape the crime scene through the vents, but didn't commit the murder.
 * Also, the air vents were used by Lamiroir to get from one side the stage to the other quickly for her part in the magic act in the middle of her song. They are stated to be large enough for her to walk, albit hunched over and there was staff waiting at either end to help her
 * As lampshaded by Spoony in his review of the The Thing videogame, at one point Blair acquires access to another room by walking hunched through a four-foot-wide air duct.
 * Lots of duct-crawling goes down in Beyond Good and Evil. Jade makes use of air vents once or twice in order to break into a few facilities, but Double H tends to do it whenever he and Jade split up in order to follow her. He literally slides out of one during the third boss fight, rocketing to the rescue.
 * The online game Infantry has a "Bug Hunt" map, allowing players to play as humans or aliens, the aliens granted the advantage of traveling by air ducts and even launching ambushes from them.
 * In episode one of Strong Bads Cool Game for Attractive People, Strong Bad must use the air vent to sneak past The Poopsmith while infiltrating the King of Town's castle. However, unlike some other examples here, you can get caught if you aren't careful.
 * Partially subverted in Wild Arms 1: only Hanpan, the little mouse sprite belonging to one of the main characters, is small enough to navigate the air vents.
 * The ship in which Dead Space takes place is blanketed with enormous, easy access vent shafts that the Necromorph enemies use to move around at will. This allows them to bypass security lockdowns and quarantines with impunity, rendering such measures useful only as an obstacle to the player. This continues into the design of the space station where the sequel is set, and protagonist Isaac Clarke gets to crawl through a few special engineer-only vents himself to get from place to place.
 * In the Rail Shooter prequel "Extraction" you do get to crawl through the vents and similar locales several times, but it's lampshaded that they are tight, cramped and hard to move quickly in. The fact you only face Leapers and Crawlers in them only makes it worse.
 * XIII has this a lot. Justified in that the player tends to machine gun all the bad guys ahead of time so there's nobody left to hear him clunk clunk through the shafts.
 * This happens a lot in Batman: Arkham Asylum. Whenever opening doors, stealth or jumps are impossible, a conveniently placed vent will always be there to be busted open to save the day, and help you proceed.
 * Sort of justified by the fact that Arkham Asylum is famous for having horrible security. Or, if you want to look at it from a different viewpoint, you could say that Bruce Wayne purposely made the vents bigger and stronger to hold him, in case he ever finds himself in a situation similar to the one in the game. Also, many of the buildings in Arkham are very old, so the vents are likely from an old ventilation system.
 * During Wolverine's escape from the Weapon X facility in the X-Men Origins: Wolverine game, he has to crawl through ventilation shafts a few times to avoid attention (thanks to his healing factor being temporarily disabled). In one of them, a guard down below yells about hearing something and starts riddling the shaft with bullet holes. Another guard tells him to stop being jumpy, and that it's ridiculous that Wolverine would be up there.
 * Shadow Complex uses vents where Metroid uses morph ball tunnels.
 * In the Myst universe we have a justified version of the mine example: D'ni is an underground city, and its Great Shaft is a huge air exchange shaft. But it's also used as the primary method of reaching the surface (or vice versa).
 * Vampire: The Masquerade Bloodlines has a series of air vents (with ladders leading to them, no less) in the garage in the Downtown area. During the mission for Fat Larry that takes you there, a stealthy character can make good use of them and avoid combat entirely- a good idea, as the enemies there are heavily armed and quite numerous.
 * In Ratchet and Clank you never actually climb inside the vents, although Clank would certainly be small enough to have one of his missions in there, but at one point you break into a building by climbing on the outside of external air vents with Magnet Boots.
 * Most of the air vents in Team Fortress 2 are inaccessible and just for decoration, but there are a few in Hydro that are big enough for players (even the Heavy Weapons Guy) to stand up in. Custom-map-made-official Turbine has an entire system these that's more of a cramped hallway than a vent.
 * Valve hangs a lampshade on this trope in Left 4 Dead 2 with the ever-epic lines of Ellis; In Dark Carnival, he says "if there's one thing video games have taught me, it's that good shit comes from crawlin' through vents". (Unlike in Half-Life the vents do not lead to anything particularly important, however.)
 * Both played straight and subverted, for unsettling effect, in Heavy Rain, where Ethan Mars character is guided by a serial killer through series of Se7en-style trials. One of them involves deliberately crawling into something that resembles both a system of wide air ducts and a dangerous exhausts vent (it sounds stupid, but looks appropriately menacing). The vent system is one foot high and branching, it's absolutely dark and hard to breathe there, and its floor is covered with broken glass.
 * This is how Rayman escapes the pirate's prison ship in Rayman 2.
 * Considering that was an air vent, which is never really explained. Judging by its size, it's more likely to be where the smaller warships are sent from, if not from the deck.
 * Well, considering that the "air vent" was in an otherwise bare jail cell...and there WAS some kind of grate in front of it...maybe it wasn't so much an air vent as an, eh, waste disposal chute. I mean, did you see a chamberpot in that cell? They probably weren't counting on the big blue guy smashing it, though.
 * Sam Fisher of Splinter Cell has an odd ability to encounter ridiculously large vents with grates off to get into areas that would otherwise be unreachable. Somehow, a guy carrying a large gun as well as a few pounds worth of other weapons and gadgets doesn't make enough sound to alert anyone. There's a particularly bizarre instance in the first game where Sam makes his way into a walk-in freezer. Given that the vent in question is connected to a regular part of the building, it means the vent is just wasting coolant.
 * The demon in Reincarnation: Riley's Out Again does this to get around the school without being spotted by humans. but it's so "tedious and unfun" that later versions added an option to skip the sequence altogether.
 * He's seen doing it again in a mini later in the series.
 * Also used in In The Name of Evil, but thankfully without the maze.
 * Used in a level in Geist; Raimi possesses a dog to get through the vents. It appears to be a boxer-type dog, and can't stand up in the vent.
 * Armored Core has the player chase after terrorist mechs who have escaped through air tunnels. In two-story tall mechs. It's sort of justified, as these are the vents that are supposed to serve an entire underground city. Just don't think about how that would actually work.
 * Mirrors Edge features a number of extremely large (and life-saving) air vents.
 * Occurs at least once in most of the Medal of Honor games, such as the last level of Mission 2 in Allied Assault.
 * Twice in Syphon Filter 2, first in the Pharcom Expo Center, then in the Agency Biolab.
 * Pajama Sam 4 has the titular character doing this at the end of the game, even though it simply leads to the ceiling of the same room.
 * Phil does this to escape his room at the beginning of Riddle School 5. He's a child, so the size issue isn't relevant.
 * While Shepard never has to enter a vent in Mass Effect 2, there are a few instances or references of vent use in the game.
 * Thane Krios uses one during his recruitment mission.
 * During the suicide mission, the chosen Tech Expert has to crawl through a duct, while the player has to fight off the Collectors in order to open the valves for him/her/it.
 * That instance should probably count as a subversion, in that the game makes very clear how very dangerous it is, and that the tech expert would have died, hideously, were it not for Shepard's help.
 * Most disturbingly, during Thanes Loyalty mission, Captain Bailey mentions Duct Rats, homeless children travel in the Citadels ventilation system.
 * A series of maintenance tunnels in The Perils of Akumos prove to be this. A separate series of air vents also prove plot-relevant.
 * Portal 2 has a variant on this: At one point, Chell uses the ductwork of old Aperture
 * The Perpetual Testing DLC features a clip of an Alternate Universe Cave warning people not to do this aboard his Prison Ship. "I don't know what nonsense you learned on TV..."

Webcomics

 * Subverted in Freefall, when Sam finds out the hard way that the air ducts on his ship are not quite big enough for him to hide in.
 * He might have succeeded if he had ditched his encounter suit.
 * Justified in Schlock Mercenary, as Schlock is a carbosilicate amorph -- he can squeeze through air vents no matter how small they are -- well, except for his eyes (standard Sphere Eyes) and his plasgun (big).
 * Justified in Gunnerkrigg Court, as the Enigmaron fortress that Antimony infiltrates is a simulation.
 * Used in this Help Desk comic, the reasoning behind such large vents is questioned and explained as Contractual Genre Blindness in the next strip.
 * Subverted in Casey and Andy: Casey sneaks in through the airvents, but is met by the Mime Assassin inside the air vents, as the villain had been expecting the plan.
 * Of course, the C&A villain Lord Milligan follows the Path of the Villain as a religion and deliberately follows every cliche. Including having giant air ducts.
 * They try the air vent route multiple times, and the mime-assassin is in there every single time. Including the last time, when they were finally expecting it, and had someone outside the vent stab through it.
 * Wonderfully subverted in this Ctrl+Alt+Del comic, given that it LEADS TO THE DEATH OF THE MAIN CHARACTER! Thus ending this Choose Your Own Adventure storyline.
 * Subverted in Questionable Content when Raven attempts to enter Coffee of Doom through the airvent and gets stuck. She's not the sharpest of minds, though.
 * Used in this Sluggy Freelance strip to sneak into Aylee's office. Justified Trope since Bun-Bun, a mini-lop rabbit is the only one who can make it through.
 * Used again in this strip. Also Justified Trope, since it's done by Rudolph the Reindeer, who has picked up all the tricks Santa uses for shimmying up and down chimneys.
 * Averted in Dead Winter. Lou's plan for getting into the store for supplies involves this method, but Monday objects on the grounds that he won't fit. Apparently he's tried before.
 * Lampshaded by the Deadpan Snarker in the improvisational comic The Omega Key on this page, where he finds it suspiciously convenient that he (a 6'10" man) can fit in an air duct. (He was right, as the destination turned out to be a trap.)
 * In Drowtales, the air vents are too small for an adult Drow. But for a child...
 * In El Goonish Shive, Noah uses air vents in the process of hunting a magical creature and the trope is discussed in the commentary.
 * Trigger from Far Out There is very good at these.
 * Nerf Now on air ducts in games vs. reality. No inescapable death trap is complete without one!

Web Original

 * Used to escape a dead-end in Survival of the Fittest by John Sheppard, Vera Lang and Kyrie Joseph, as killer Harry Tsai was hot on their heels and it was the only way out of the building they had run inside.
 * Shelton and Ridgeway successfully do this in Darwin's Soldiers: Schrodinger's Prisoners. It's also subverted in the third RP when Hans suggests this as a way to get into Pelvanida and James points out how that wouldn't work.
 * Tech Infantry has a sequence where a space station is captured by rebels, and they lock Xinjao O'Reilly, the chief engineer on one of the space docks, in a tool storage closet with his engineering crew. They hang a lampshade on what a stupid move this is, grab a bunch of tools, and escape into the maintenance passageways between bulkheads. They make life very difficult for the rebels controlling the station for a while.
 * Played straight in Magical Girl Hunters when sneaking into the Mashihaishi Ultra building. The confusing layout is lampshaded with Yoi asking directions of other people traveling through the same vent system.
 * Mercs has this done by Varisa and Creed to sneak around the ship during the "Hijack" episode. At one point, one of the mooks tracks Varisa by the banging noises in the ductwork and ambushes her when she comes out.
 * In The Motley Two, the spaceship "Hiroja" has vents big enough that the characters can sneak around the entire ship with impunity. Perria Makara, who snuck aboard undetected, even sleeps quite comfortably in the vents (near the heating unit).
 * Duct Hunt, a parody of the Metal Gear series, deconstructs almost every aspect of this trope.

Western Animation
"Groundskeeper Willie: Lunchlady Doris...'ave ye got any grease? Lunchlady Doris: Yes. Yes we do. Groundskeeper Willie: (tears off his clothes) Then grease me up, woman! Lunchlady Doris: ... Okee-dokee."
 * Beast Wars: Cheetor goes through the ventilation shafts of the Predacon ship after having been accidentally transported to The Darksyde in "Equal Measures".
 * Transformers Generation 1: Used in "The Ultimate Doom" when Spike and Bumblebee fall into a trap on Cybertron. Brawn joins them and they go through a ventilation shaft that takes them to Decepticon HQ.
 * This is a favorite route of the girls in Totally Spies! for breaking in, clearly thanks to Male Gaze.
 * Kim Possible and Ron infiltrated this way in The Movie. They do it quite a lot during the series.
 * Recess: T.J. often uses this route to break himself and occasionally others out of detention.
 * Teen Titans is an exception; Titans Tower's quarantine lock-down system apparently does seal off openings to the air ducts, as seen in the episode "Haunted". (Of course, Robin got into the vents anyway....)
 * Subverted in the same series: Cyborg is attempting an Air Vent Infiltration in the episode "Wavelength" when the walls roll up and the thing rotates, dumping him into an arena and a battle with Bumblebee which he very nearly loses. He should've thought twice about even coming across a vent big enough for his 6-foot, 200-pound chassis.
 * Ben 10 did this a couple times, though it's Justified Trope by the fact that, both times, Ben was transformed into an alien form that was five inches tall and gave him greatly enhanced brainpower.
 * In a Jem episode, Jem, Aja, and Shana do this to escape a locked room.
 * Spider-Man: The Animated Series constantly had Spidey doing this. During the Venom arc, after Peter finds the symbiote and experiences drastic changes to his personality, he considers but chafes at using the trope, saying "That's the old Spidey thinking." He instead goes for the direct approach: kicking the steel door down and barging into Kingpin's meeting.
 * The Transformers Generation 1 episode "The Ultimate Doom, Part 2" introduced ventilation ducts large enough for Transformers to stand inside. Of course, they're on Cybertron, where everything is of the same scale as Transformers are to humans, but why would they need air anyway?
 * And pulled again in Transformers Animated, episode "Decepticon Air". Optimus Prime crawls through the ducts (it seems to be a squeeze, letting him homage Die Hard as well) of a spaceship -- maybe the air circulates to keep the energon from heating up and getting unstable? He does use it as a makeshift bomb, after all.
 * Peter and Brian do this in an episode of Family Guy, complete with a Shout-Out to Die Hard.
 * They don't make it all the way in stealthily, though, Peter's large girth causes the vent to give out and dump them right in the middle of the prom.
 * Subverted in Futurama. Fry and Bender try to escape from a brig through a steam pipe vent. Unfortunately, the steam pipe is full of steam. At least they got a good sauna out of it.
 * Lampshaded in Bender's Big Score. While trying to destroy a "Death Star", Al Gore's head in a jar flies a through an air vent actually labeled "Achilles' Vent", lasers a-blasting, successfully destroying it.
 * In Bender's Game, Fry and the other travel around Mom's factory through a tube that sends chickens to the enslaved Nibblonians. It works, but they have to shove their way through a lot of chickens.
 * Lampshaded and subverted in an episode of Buzz Lightyear of Star Command, when Emperor Zurg chews out the designer of his latest evil lair for making the air ducts big enough for heroes to fit through.
 * Subverted in Avatar: The Last Airbender. The Gaang was stuck in a room and the only exits were air tubes, so they tried to get Momo through it. However, Momo ate too much, and couldn't fit.
 * Momo later did crawl through some tubes in Roku's Temple, though it wasn't actually an "escape".
 * Parodied in the 100th episode of The Simpsons. Santa's Little Helper gets into the school ventilation shafts, and only a greased Scotsman can catch him....

"Homer: [scribbling on pad] I love spying. [Terrorist picks up a bar of uranium. Radioactive gas boils off the surface of the rod] Burns: Don't worry about those fumes. They'll be sucked into that air vent. [Homer moans from fumes, drops pad out of vent and onto the floor]. Burns: This place is falling apart. [walks over, picks up pad and shoves it back into the vent]"
 * "There's nary an animal that can outrun a GREASED SCOTSMAN!"
 * This is how Homer spies on Mr. Burns meeting with terrorists, and would be caught if it wasn't Played for Laughs:

"Robotnik: Tell me, Snively, how did the hedgehog get past all my security?
 * In one of Homer's daydreams where terrorists take over the plant, Homer jumps from a standing position into a vent on the ceiling, then comes out in Burns' office to beat the terrorists up.
 * Chip 'n Dale Rescue Rangers uses this in a few episodes. Then again, the use is probably justified as the Rescue Rangers themselves are only around 10 cm tall.
 * In Sonic the Hedgehog, most episodes that contain Robotropolis have the main characters in an air duct at LEAST once. Robotropolis is perhaps Air Duct Central, essentially one giant factory bathing in its own heated (polluted) air. Lots of cool (polluted) air has to be moved around to keep the place from overheating somehow. By the way, Robotnik hates this trope:

Snively: Through an air duct, Dr. Robotnik.

Robotnik: An air duct? Then SEAL IT OFF!!"


 * In the Code Lyoko episode "Canine Conundrum", Yumi and Ulrich escapes from the Gymnasium (besieged by robot dogs) this way. Although there is a joke, previously, about the adult teacher, Jim, being too fat to follow them.
 * Given her size, Jade from Jackie Chan Adventures utilizes these at times to get around places when no one else can. The episode "The Day of the Dragon" feature both her and the Dark Hand using the air vents to escape Section 13.
 * Defied Trope in Wolverine and the X-Men: Wolverine and Gambit are trying to break into a secret lab to steal back a power inhibitor collar, and Wolverine suggests taking advantage of this trope. Gambit counters with: "Heh, only in the world of cinema. In real life, they never hold." It certainly doesn't help that Wolverine's metal skeleton makes him about three times as heavy as a normal person.
 * Parodied and subverted in Batman Beyond: The protagonist enters a vent large enough to walk in, but the subsequent sections keep getting smaller and smaller.
 * Danny Phantom: In the episode "Doctor's Disorders", the only way to save the hero so he can stop the villain is to go in by the way of an air vent.
 * The Dennis the Menace UK cartoon does this in one episode when he's trying to flee with Gnasher from a large mobile mall that has arrived in Beanotown and hypnotising everyone into buying useless junk. Whilst crawling, they find the office of the mad scientist behind the plot, and instead of escaping Dennis decides to bring him down instead.
 * Subverted and played with in Batman: The Brave And The Bold: Batman is infiltrating a parallel Earth, disguised as his evil counterpart Owlman. He's allied himself with Red Hood, the heroic counterpart of the Joker, who is being tortured by Silver Cyclone, the evil version of Red Tornado. Batman sneaks through the air vents to free Red Hood and escape after his cover is blown by the evil Atom. This might have worked... EXCEPT Silver Cyclone apparently had a tracking device or something on Batman, because the moment he realizes that Red Hood has been in contact with someone, he remembers that Owlman has been acting strangely and his computer immediately tells him Batman's location, in the air vents, proving that he's a spy. Silver Cyclone then powers up the fan to slice "Owlman" to pieces. Of course, this is the goddamn Batman we're talking about, so he blows up the fan. But still, the Air Vent Passageway escape turned out to be not the best idea.
 * Averted in "Menace of the Conqueror Cavemen!", as the air vents are cramped. They also shake and make a good deal of noise when Batman and Booster crawl through them. Fortunately Kru'll isn't paying much attention.
 * In an episode of Max Steel, the only entrance to a highly-secured building is through the air vents. The only way in is by careful timing to avoid being sliced by a giant fan; the vents end two-thirds of the way up the wall in a room where the floor is littered with explosive devices, and not only do the air vents have cameras, they're also equipped with flamethrowers the big bad of the episode can activate at will.
 * Robot Chicken Lampshaded this in an Iron Man spoof. Two Mooks guarding The Mandarin's lair are able to instantly determine that the deafening banging and screeching noises they hear are from Iron Man trying to sneak through the air ducts.
 * Jonny Quest episode "Mystery of the Lizard Men". Jonny crawls though an air duct to escape from the title opponents.
 * SpongeBob SquarePants, "Truth or Square": after getting locked inside the Krusty Krab freezer, the gang makes their way out through the restaurant's labyrinthian ventilation system.
 * Subverted in the Jimmy Two-Shoes episode "Jimmy in the Big House", when Jimmy and Beezy tries to get out of prison by going through air vents. Suddenly, a screen pops out and it's a video message from Heloise who lets them know that they have made it far in escaping but in her prison, there is NO ESCAPE! As a result, they are blown out of the air vents by the fans at high speed and back to where they were. In this case, it's probably justified since Heloise probably made the vents that big just to crush prisoner's hopes for escaping.
 * Star Wars: The Clone Wars, loves this trope.
 * Ahsoka once escaped Griveous this way.
 * Ventress used the airvents to infiltrate and sabotage a Republic Star Destroyer unnoticed.
 * Cad Bane infiltrated the Jedi Temple through the airvents. Doubles as Absurdly Spacious Sewer.
 * Ahsoka Tano and Barriss Offee escape from mind-controlled Clone Troopers by jumping into the air vents. Later in the episode, Ahsoka uses the same vents to travel to the coolant control room and the bridge while she's running from Barriss.
 * Aura Sing used these to attemp the assasination of Padmé.
 * Subverted and lampshaded in the episode "The Citadel". With the entry point the Jedi wanted to use blocked, Anakin and Obi-Wan muse how to get in, and Ahsoka points on the ventilation hatch. Anakin argues that they're too small to gain acess, but in response Ahsoka points out, that they might be too small for Anakin, Obi-Wan and the clones, but she might be able to squeze through -which of course she is, althought barely. In the next episode Obi-Wan's entire team tries to escape the Citadel in absurdly spacious airvents. However these had leathally effective security doors, and the warden at least had enough common sense to send at least one drone in the airvents.
 * In the first season finale of Exo Squad, after taking their attempt to use Phaeton as a hostage fails, Able Squad escapes the Brood Chamber via the air ducts. Typhonus responds by sending troops into the tubes; why the tubes were made big enough for Neosapiens to walk around in isn't explained. Then he reroutes the ventilation so the tubes are flooded with poisonous "volcanic gas". Exactly why the heck someone would build a ventilation system that allows that isn't explained either.
 * Space Ghost episode "The Space Piranha". Jan and Jace infiltrate an enemy base using the ventilation system.
 * Justified in The Batman when Ragdoll uses it; he is the most flexible person to have ever lived, and the air vent only needs to be big enough for his head to fit in, as many air vents are in Real Life.
 * Sam and Max, and Sam's granny Ruth, try to reach the prison warden this way in the Sam and Max Freelance Police episode "Christmas, Bloody Christmas" -- only, instead of the air vent, they go through the prison's water duct, and end up in the shower room.
 * The Amazing Spiez use this technique in episode "Operation Spy-Sitter".
 * Wallace and Gromit's The Wrong Trousers had air ducts to a museum big enough to stand in. They were realistically loud though, insofar as a pair of remote-controlled, vacuum-soled robotic trousers can be realistic.
 * Birdman episode "The Quake Threat". When Birdman is trapped in an Elaborate Underground Base, Avenger the eagle breaks in to save him through an air vent.
 * Zadavia stages one on Deuce's ship during the Loonatics Unleashed episode "In Search of Tweetums, Part II".
 * Subverted in X-Men Evolution, As the vent was only a few incles long, big enough for people to climb into, had a ladder inside, & Blob got stuck, however it also had a large amount of security lids which Cyke was able to close to keep Mystique from escaping.
 * Played with in another episode. When the group was testing out the security of the mansion, Wolverine is able to go to many parts of the mansion through the vents, and suggests something be done about them.
 * Archer is fond of this. Somewhat surprisingly, it's always played straight.
 * Played straight in The Problem Solverz episode "Badcat", when the solverz travel through a vent to reach Bad Cat's lair on the top floor of his casino.
 * Lampshaded near the start of Titan A.E. when Korso tells Cale to head for the vents. Cale responds sarcastically that no one would think to look for them there.

Real Life

 * To this day, criminals will attempt this trope at any number of buildings where they can find a suitable opening. The difficulty they will encounter is that ducts don't stay the same size or shape all that often. The added difficulty of straight up-and-down ducts will see many criminals slipping and falling to become wedged or even killed by the fall.
 * Even worse for some criminals is they may attempt this on holidays or weekends to avoid being heard clambering through the ventilation. When they become trapped, they must wait days without food or water in extremely uncomfortable positions for somebody to discover them.
 * In Real Life, small animals tend to be more successful at this trope than humans (they're small enough to get inside easily, they're light enough that the ducts can support their weight and they don't make as thunderous a noise while they move around).
 * Depending on the animal, they can still be very loud as claws or nails make a racket running on metal.
 * During and around The Dung Ages, a popular way to infiltrate a stronghold was to climb through the privy chute. This had varying outcomes; either they made it, and incidentally killed Edmund II by puncturing his arse, or they got stuck and died in there, or they suffocated and then died in there. After such sieges, those chutes had to cleaned elaborately and swept through because of all the stuck-up cadavers.
 * This was attempted in 1994 by Cleveland Indians pitcher Jason Grimsley to try to switch out teammate Albert Belle's corked bat before the umpire could find out he was cheating. Going through 10 feet of ducts and a false ceiling, he might have even gotten away with it if he hadn't replaced it with an autographed bat.
 * Averted in real life: Sensitive Compartmented Information Facilities, a.k.a. SCIFs, where top-secret intelligence information is handled in the United States have a list of regulations on construction of air vents, including grates to prevent entry and deliberate metal disconnects to avoid sound transfer.
 * Successfully done by serial killer Ted Bundy. While in prison awaiting trial on one of many murders he was suspected in, he climbed through the roof of his cell (he had dieted and lost enough weight to make this possible), crawled across the floorboards into the adjoining warden's apartment (the warden and his wife were out at a New Year's Eve party), and simply walked out of the apartment into freedom. He was caught several weeks later, but not before adding several more victims to his list.
 * When Kingsley Ofosu and 8 other Ghanians stowed away on a Europe-bound cargo ship, he escaped from the ship's murderous crew (the other stowaways were not so lucky), by shimmying up one of these.
 * Quantay Adams managed to escape from a jail by going into the subceiling and out through a vent. It was harder than it sounds; after getting a hacksaw blade to get through the ceiling, he had to both time the guards, evade the cameras-including the one in his cell-and get to his accomplice outside. His grand total of freedom? Seven hours.
 * On a G4 special one of the famed Bioware doctors mentioned how as a child his teacher locked him in the closet for misbehaving, he climbed from the closet into the drop ceiling Breakfast Club style. After crawling back into his classroom he positioned himself over where the teacher was standing and dropped a lugie on them.
 * Attempted unsuccessfully by Jamie Minor. She tried sneaking into her workplace by the air ducts but got trapped.
 * Inverted -- if only just -- in real life basements containing an 'egress window'. This is intended to assist folks in their escape in the event of a house fire or emergency, but many folks often leave it open to get some air circulation going. Furthermore, many people are too large to make proper use of them.