Air Vent Passageway/Playing With

Basic Trope: Air ducts are used to escape a prison cell or sneak around enemies.
 * Straight: Bob uses the vents to get out of his cell.
 * Exaggerated: Bob escapes through the vent... along with every other prisoner in the prison.
 * Justified:
 * The ducts are large to funnel large amounts of air and reinforced to survive an earthquake.
 * Bob is an air-conditioning engineer, or otherwise knows how to get out safely through unconventional means from a building.
 * Inverted: Bob's captors seal him inside the air vents, reasoning that he'll never find his way out.
 * Subverted: The ducts turn out to be too small for Bob to fit through.
 * when the guard enter the cell, they don't see Bob and entrance for the vents is open. But when the guards look at the vent, Bob, who was hiding under his bed, knock them from behind.
 * Double Subverted: The ducts are too small for Bob to fit through, but that's only because they're the local ducts. The central vents, needing to handle lots of air, are much larger.
 * Parodied:
 * Air vents are the main form of transportation in the facility; corridors are essentially unused, making them the sneaky way of getting around.
 * The air vents are a network of huge tunnels, complete with water fountains and maps of the building.
 * Deconstructed: Bob comes close to being badly injured by a fan he tries to jump through. He realises he has no idea how to find his way around, and starts panicking that he'll be trapped for ever. However, the ductwork transmits the sound of his movement throughout the building, and his captors catch him in minutes.
 * Reconstructed: Bob only uses the ducts after exhausting every other option, and is careful to stick to the larger, stronger vents. Knowing he won't be able to sneak through them for very long, he uses them just to get into the nearest corridor.
 * Zig Zagged: The local vents are too small, but the central vents are large enough. However, the vent cover on them is too tightly secured. Luckily, another large vent runs just under the floor.
 * Averted: Bob never even considers the ducts.
 * Enforced: The director wants his movie to be Troperiffic.
 * Lampshaded:
 * "Oh, great, am I going to have to crawl through the vents?"
 * "If I ever run a prison, I'll secure the vents"
 * "Why is it always ducts?"
 * Invoked: "The tracker is installed. We should let Bob escape, but it needs to be hard so he thinks he's gotten away." "Let's put a conveniently large vent leading to his room."
 * Defied: "Go in the vents? That's the first place they'll look for escapees!"
 * Discussed: "I happen to know that this building has extra-large, reinforced air vents, specifically installed to provide the inhabitants with a means of emergency exit." "Fantastic! How do we-" "Yeah, they aren't hooked up to the prison cells. These guys aren't morons."
 * Conversed: "You just wait and see; he'll go into the ducts eventually."

The way back to Air Vent Passageway is too heavily guarded. Looks like we'll have to go through... oh, how did you guess?