Air Hole

Air Holes, found below planet Zebes' surface, are artificial pipe-like structures protruding from floors and walls. They come in a range of colors, with some featuring slightly different designs. They are mostly known for the infinite number of small hostile animals that fly out of the opening when approached, which imply that the inside of Air Holes contain nests. Few of them are merely decorative, and fewer still can be entered by Samus. Air Holes are only seen in Metroid, Metroid: Zero Mission and Super Metroid.
=== Metroid ===
In the original game, Air Holes have a universal design with differing shades of blue or red colors. Nearly all of them are inhabited by organisms that display the same aggressive behavior of flying upwards from the pipe until they are on the same level as Samus, and then immediately dashing in a horizontal line to ram her. Each Air Hole releases a single enemy at a time, and the next enemy will not appear until the previous one is no longer present onscreen; if a pickup appears from a slain creature, the pipe will cease to spawn further entities until the pickup either disappears or gets collected by Samus. Freezing these creatures with the Ice Beam will also temporarily disable their respective Air Holes. The species living within these structures are unique to each region of the planet:
* Zebs in Brinstar
* Geegas in Kraid's Lair
* Gamets in Norfair
* Zebbos in Ridley's Lair
If multiple Air Holes are placed next to each other, jumping over them unscathed can prove to be difficult due to the rapidly emerging enemies that may hit Samus from below, and her jumps are likely to cause each spawned enemy to fly at different altitudes, making the mere act of evading their attack from a distance a tricky task. These issues are resolved once the Screw Attack is acquired. As Energy Tanks or Missile Expansions become scarce, Air Holes provide the only reliable means of replenishing Samus's health and Missile ammo via the pickups that often materialize when Samus kills the unceasing quantity of creatures.
=== Super Metroid ===
Air Holes have two different designs, with the first bearing either a green or red color with a shape not too dissimilar to the original from Metroid. The second design is a brown pipe with ridges lining its opening. Unlike other games, some Air Holes are found protruding on walls. All spawned enemies maintain the same attack pattern but are quite sluggish in their movements, diminishing the overall threat of these structures. Some creatures can now come out in droves however: when initially emerging from an Air Hole's opening, they appear as a single entity before they spread out vertically to reveal a total of five individuals. Air Holes that release such groups are the most valuable to Samus if she wishes to collect many pickups quickly. The organisms inhabiting the structures are not found in the same environments as the first Metroid game and each species is no longer tied to a single region, with some like the Zebbo being found in three areas.
Despite the introduction of charge stations which offer a far quicker method of replenishing her resources, their scarcity enables Air Holes to retain their usefulness, even more so when taking into account the complete lack of such stations for Super Missiles and Power Bombs.
==== Natural Air Holes ====
Also introduced in Super Metroid is the existence of naturally formed crevices throughout Zebes that continuously release the same kinds of animals as the artificial pipe-like structures. These can be regarded as natural Air Holes and they vary immensely in appearance, from small mounds of earth to fissures made from Norfair's glass bubbles to even offscreen burrows often filled with either lava or acid. The area known as Maridia features underwater crustaceans called Zoas that emerge exclusively from sandpits but nonetheless fall under the same category as all other Air Hole enemies due to their limitless spawning and identical attack pattern, though their groups swim in a single file instead of spreading out in a vertical formation. Finally, there are some large carnivorous plants known as Samus Eaters that serve the same function as all previously mentioned crevices and pipes by having endless amounts of Zebbos emerge from their mouths, making those plants living Air Holes.
=== Metroid: Zero Mission ===
Both artificial and natural Air Holes appear in the remake of Metroid. The former come in a greater variety of colors, adding green, orange, pink, purple and grey alongside red, though the blue color has been removed entirely. The same list of Air Hole enemies for each region is preserved from the original game, as well as their quick speed. Some organisms are released in single line groups like the Zoas from Super Metroid.
=== Miscellaneous info ===
While it can be interpreted that most pipe-like Air Holes connect to vast, unseen systems or sections of terrain that contain the innumerable creatures, all games feature instances where that does not seem at all plausible. Some Air Holes protrude out of small floating platforms, seemingly making it impossible for more than a couple of creatures to live within it, yet they ceaselessly continue to emerge from it when Samus is near. This gives the impression that the animals materialize within it.
There are only a handful of Air Holes that Samus can enter in Super Metroid and Metroid: Zero Mission combined. In the former, there's one located on a wall in Brinstar leads to a Missile Tank. Another Air Hole in the same area breaks into Pit Blocks when Samus stands on it, revealing a long vertical shaft under it that leads to the game's first Super Missile Tank if no Sequence Breaks are used. In Zero Mission, there are two sets of empty Air-holes in Ridley's Lair that lead to expansions. One houses a secret area leading to Missile Expansion while another leads to an Energy Tank. Some of the sandpits from which Zoas float out of in Maridia hide shortcuts.
== Similar structures ==
=== Metroid/Metroid: Zero Mission ===
There are other artificial structures on the ground found only in Norfair that share more or less the same function as Air Holes, though these have a very different appearance and strictly spawn Polyps.
=== Super Metroid ===
A hostile entity known as Puromi emerge from offscreen crevices on the ground.
=== Metroid II: Return of Samus ===
On planet SR388, there are several corridors containing vine-like tunnels on the floor that infinitely release Gawrons, Skreeks or Yumees, serving exactly the same function as Zebes' Air Holes. In some areas of the planet, these creatures will emerge from pools of hazardous liquid. However, they will cease to fly out from their respective nests whenever 10 of these are killed, suggesting that either the creatures have chosen to preserve their lives rather than continue to face Samus, or she managed to wipe out the whole colony. A strange noise will notify her of a "depleted" Air Hole.
=== Metroid Fusion ===
Aboard the Biological Space Labs are pulsating cylindrical openings on the ground from which harmless Hornoads jump out of in the background. They provide a limitless supply of hosts for the X Parasites to infect, turning them hostile against Samus but also providing her with a convenient farming location to replenish her resources.
=== Metroid Prime series ===
There are instances in Metroid Prime and Metroid Prime 3: Corruption where creatures are continuously spawned from pipes or other small crevices, essentially acting as the 3D equivalent of Air Holes. The Puffers, Plated Puffers, Puffer Mines, Phazon Puffers and Phazon Metroids are infinitely spawned within the Phazon Mines Ventilation Shaft, Tower of Light, Airshaft, Drop Shaft and Metroid Cavern, respectively. 
In Metroid Prime 2: Echoes, an unscannable device known internally as a "Puffer Port" behaves like an Air Hole, spewing out an infinite supply of Preed or Dark Preed within the area these devices are housed in, but only two Preed/Dark Preed can be spawned at a time from these devices. The pipe device is made up of a small shieldless door surrounded by a metal ring, with the unit situated on a wall. These air pipe-like devices can be destroyed with Missiles. They are seen within Hydrodynamo Station and Undertemple Shaft respectively. Because there is no further covering behind the port's door, whenever a door opens, it gives off the appearance that Preed/Dark Preed are appearing through a solid wall. Oddly, one of the doors in a set does not open properly, making the creatures spawn from a closed door.
==Trivia==
*Air Holes strongly resemble Warp Pipes from the Super Mario Bros. series. Indeed, in Victory Techniques for Metroid, Samus mistakes one of them for a Warp Pipe, and manages to partially enter it before a Zeb's horns stab her from underneath. Interesting to note is that the short story is based on the original Metroid game where no Air Holes were enterable.
==Gallery==
Image:Pg048-049.jpg|How not to use an airhole. (Victory Techniques for Metroid)
Screw Attack Geega Air Hole amiken Ryu.png|Geega spawning from an Air Hole in Famiken Ryu.
Image:Metroid 2.png|Red air hole and a Zeb in Metroid.
Image:SM Brinstar AirHoles.png|Two Air Holes and a frozen Geega in Super Metroid.
Puffer Pipe Model.png|"Puffer Port"
Puffer Pipe Inner Ring Model.png|The outer ring's backside of a Puffer Port, its inside markings seen without the door.
Hydrodynamo Station Puffer Port open.png|The Puffer Port opens, releasing a Preed.
Category:Obstacles
Category:Zebes
Category:Brinstar
Category:Norfair
Category:Hives