A special [[DeflectorShields forcefield]] that prevents a [[GoingCritical highly volatile power source]], anti-matter engine core, enslaved magical beastie, an orb of Main/PureEnergy, etc., from obliterating everything around it in a flash of pure white. Maintaining the Containment Field is the most important job of the starship's engineer, the wizard's acolytes, or the Main/BarrierMaiden / [[BarrierWarrior Warrior]]. Inevitably, the Containment Field will begin to weaken, leaking dangerous radiation or reality-warping magic all over the place, and forcing the heroes to drop what they're doing and scramble to restore it (often [[SomeoneHasToDie sacrificing themselves]] in the process).

Should the heroes fail to restore the field, they may be forced to eject the engine core. Doing so will cripple their ship and leave them defenseless, but it beats certain death by vaporization. In the case of a beastie, it's FinalBoss fighting time.

Note that engineers in RealLife prefer to design things with "inherent safety" in mind, so that if something goes wrong they shut down - or at least fail in a controlled way rather than explode spectacularly. For example, modern nuclear reactors are designed with the control rods suspended over rather than under the reactor, so that if power is lost to the electromagnets they all fall ''into'' the reactor and stop the fission process, rather than ''out'' of the reactor to cause a runaway reaction. Redundant safety systems are also encouraged if a process relies on them for safe operation. This can lead to some examples of Containment Fields (especially sci-fi ones) being a case of ArtisticLicenseEngineering but hey, RuleOfCool.

The Containment Field often consists of an energy barrier -- similar to Main/DeflectorShields, but on the inside of the ship, and facing inward -- though this is not always the case.

A Containment Field is a vital part in many [[Main/SummoningRitual Summoning Rituals]].

See GoingCritical. Compare SuperPowerMeltdown.

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!!Examples

[[foldercontrol]]

[[folder: Anime and Manga]]
* In ''Manga/{{Akira}}'', the cryogenic suspension chamber [[spoiler: that houses Akira's remains]] acts as a Containment Field, and, naturally, begins to fail towards the end of the movie. [[spoiler: Akira unfreezes, allowing him to return and destroy almost all of the city... again]].
* The use of a magnetic field (called an I-field in this universe) compressing the reactants is how most Franchise/{{Gundam}}s are able to fit a fusion reactor (which should, by all rights be the size of a small city) into a mech the size of a small building. As an added bonus, this means if said field fails we get to see StuffBlowingUp.
** These containment fields are also responsible for most of the Mobile Suit's EnergyWeapons, drawing particles from their reactor and using pressure from the containment field to fuse them into heavier particles, which can then be harnessed as various kinds of particle beams. The [[WaveMotionGun Beam Cannon]] and [[LaserBlade Beam Saber]] are both applications of this technology.
** The 'Mechs and some high-tech vehicles of TabletopGame/BattleTech run off of small fusion engines the same way. The game rules assume that they simply shut down when damaged, instead of blowing up dramatically. Official but optional rules for cinematic explosions or the somewhat more plausible possibility that superheated plasma squeezed hard enough will rapidly expand if the pressure is taken away; not an explosion, but just as lethal to the 'Mech it happens to (less so to others).
* In the [[ComicBookAdaptation supplementary manga]] of ''MagicalGirlLyricalNanoha'', if the characters are training and he's around, [[BarrierWarrior Yuuno]] creates these to minimalize damage to the surrounding area. Of course, since his fields are trying to contain the attacks of some very trigger-happy [[PersonOfMassDestruction Persons Of Mass Destruction]], these tend to get destroyed.
** Containment Fields are used in the first two seasons of the anime to contain magical beings within an area while keeping out non-magical beings who may be harmed in the battle, with Nanoha's ability to break a barrier as a significant element in second season. As the third season and beyond are set in worlds where [[EveryoneIsASuper even the innocent bystanders are magical beings who would be caught in them]], these are rarely used.
* Unique example in ''GaoGaiGar''. Rather than make a barrier of some kind, the Dividing Driver "shoves" all materials out of its area in circular radius save for the HumongousMecha and the MonsterOfTheWeek.
* In ''Manga/HellTeacherNube'', [[TheRival Tamamo's]] DangerousForbiddenTechnique, [[MeaningfulName Megiddo]], unleashes a monstrous blast of destructive magic at its foe. In order to prevent damage to the vicinities (and conveniently focus all its power on the foe,) Tamamo splits his [[WeaponOfChoice bladed staff]] into four pieces around the target, generating an [[SphereOfDestruction egg-like field of annihilation]].
* in ''RahXephon'', [[YearInsideHourOutside Tokyo Jupiter]] was created by the Mulian forces by erecting a perfectly spherical field (with a swirling surface reminiscent of Jupiter's stormy atmosphere) around Tokyo, sealing it off from the rest of the world. Piercing it is a herculean task requiring tremendous energy expenditures and specialized equipment... or a godlike mecha. Whichever is easier to acquire.
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[[folder: Comic Books]]
* ''ComicBook/TeenTitans'', supposedly the only thing Kid Flash can't escape from.
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[[folder:Film]]
* When a ghost is captured in the ''Film/{{Ghostbusters}}'' films, it is then deposited into a laser containment grid. The light is green, the trap is clean.
* The EU technical explanation for how a lightsaber in the ''Franchise/StarWars'' movies work is that a lightsaber blade is plasma energy suspended within a containment field.
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[[folder:Literature]]
* The magnetic cage[=/=]trap in ''AngelsAndDemons'' keeps the antimatter suspended in a vacuum, to prevent it from touching any regular matter and annihilating in a giant kersplosion of pure energy. Of course, some asshole has to go and unplug it. Luckily, it has a battery-backed UPS built-in.
* The fusion reactors in ''Literature/HonorHarrington'' work by hyper-compressing the reactor plasma in "gravitic bottles." This has the effect that if said containment bottle is lost, [[JustifiedTrope even though David Weber is fully aware that a breached fusion reactor stops reacting]], the sudden release of pre-existing heat and pressure is more than enough to [[GoingCritical make a truly scary kaboom]].
* In the ''Literature/HyperionCantos'', containment fields are EVERYWHERE, and they are powerful. For example, it is noted that while the Hawking Drive is running, containment shields must be up at all times. Should they fail for even a microsecond, especially during acceleration and deceleration, all passengers on board would be compressed into a pile of jelly. Shields range from Class 1s, which can act as a seatbelt, to Class 10s, which deflects all radiation and even nuclear explosions and asteroids.
* In TheWheelOfTime the Dark One has both the seal the Creator established around him, and then [[NiceJobBreakingItHero it's pierced]] in the attempt to tap into a new form of magic, and the resultant hole is patched. Making it a containment field on a containment field.
* The EnchantedForestChronicles contains an interesting example: [[spoiler:The Wizards erect a magical barrier around the castle that contains the [[KingInTheMountain sleeping king]], one through which only they can pass. The Dragons erect a similar barrier (except that only ''they'' can pass through it) to keep the Wizards from doing whatever they want with the castle.]]
* The suspensor field in ''TheHistoryOfTheGalaxy'' series is an interesting case. The field doesn't do any containment by itself, as it's too weak to hold anything large. What it does is take any dust particles or grains of sand or anything else small and press them together to form a barrier. Used on spaceships to seal off hull breaches, during digs in desert areas, etc.
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[[folder: Live Action TV]]
* The Warp Core on every ''Franchise/StarTrek'' ship is encased in a Containment Field, which fails with depressing regularity.
** Generally just becomes in danger of failing (often due to very heavy damage), since failure means a CriticalExistenceFailure unless it is ejected. The same goes for the antimatter storage.
** And the ejection systems almost ''never'' work.
** There is also the use of force fields which work on a similar principle to the DeflectorShields and are used for everything from emergency containment of hull breaches to security and isolation fields.
* The Slipstream Core on ''Series/{{Andromeda}}'' is very similar, but, perhaps, even more volatile.
* The main fusion reactor of ''Series/BabylonFive'' is maintained by elaborate machinery which acts as a Containment Field.
** It is never really talked about or in danger of failing. Only once did a homicidal maniac slap a bomb to it big enough to "blow through to the reactor", and in an alternate future that never happened Garibaldi "rigged" the reactor to blow. In 2280, when it is scuttled, the explosion clearly originates from the reactor. The words "Containment" and "Field" are never uttered together in either of those instances.
* In ''Series/StargateSG1'' any Replicator held in a containment field is guaranteed to escape.
* Given that its main characters are fugitives, ''Series/{{Farscape}}'' didn't have too many encounters with these. However, in "Die Me Dichotomy," a visit to Diagnosan Tocot's facility reveals that the operating theatre is equipped with a shield that's designed to keep contaminants ''out'' of the area, partly for the safety of the patient, but mostly to prevent Tocot from becoming infected while working without his protective mask.
-->'''Grunchlk:''' You see the green light? That's a biological neutralizer, that is: you could have [[ThePlague the Karatonga plague]] in here, wouldn't touch him. Anywhere else? Pick yer nose and he's dead
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[[folder: Video Games]]
* In the ''VideoGame/{{Crusader}}'' games, this trope is often inverted because of NoOSHACompliance. While most of the reactors are shielded, most of the shields seem to be one-way; so the workers can get radiation poisoning but marauding rebels can't just blow 'em up.
* The final chapter of ''VideoGame/HalfLife2'' is based around this trope.
** The first part of ''Episode 1'' deals with re-activating a containment field on the Combine's Dark Energy reactor, which is melting down. Surprisingly, reactivating the field does ''not'' resolve the situation: the reactor is already too far gone to be salvageable, and is going to explode anyway. The field will just delay the process.
** The reactor (stated in-game to be a "dark fusion" reactor) was deliberately sabotaged by the Combine itself (the people who built it), and they set up a system to harness the energy of the detonation to create a super portal back to the Combine universe. So that's the reason why it blew up, not because it was ''GoingCritical'', but because it was deliberately configured to explode.
* At the end of ''MightAndMagic 6'', you must cast a spell of Dark Containment around the machine you have to blow up. Otherwise you destroy the world, an epic FAIL after about 100 hours gaming.
* The only time in the ''Franchise/{{Ultima}}'' series that the story calls for casting Armageddon, the Avatar first performs the Barrier of Life ritual, to contain and focus the world-shattering power.
* The maps of {{Hawken}} have a transparent blue force field surrounding them, to prevent players from leaving the confines of said map/s. A possible in-universe explanation is that the fields are used to keep the "Giga Structure" inside the contaminated areas and prevent them from spreading.
* Activating and maintaining one of these is part of an engineer's everyday job aboard ''VideoGame/SpaceStation13'', as they keep a [[UnrealisticBlackHole gravitational singularity]] from devouring the station. Of course disabling that field is very popular amongst [[TheMole traitor players]].
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[[folder: Web Comics]]
* The Gates in ''Webcomic/TheOrderOfTheStick'' keep the local [[EldritchAbomination god-killing abomination]] at bay by patching up tears in the fabric of reality, which serves as its prison.
** [[RunningGag Gate? What gate]]?
* In ''Webcomic/SchlockMercenary'', power reactors use gravitic fields to keep neutronium compressed at incredibly gigantic density. When the fields fail, or are undone, they make a distinctive SKOOM noise and [[StuffBlowingUp a great big hole in the world]].
[[/folder]]

[[folder: Web Original]]
* Magmatter in ''OrionsArm'' needs to be kept in place by magnetic fields, since the stuff tends to destabilize atomic nuclei. It is a primary structural reinforcement for megascale structures, but it doesn't usually react with matter, instead passing through 99.9% harmlessly. It's very complicated, though a dozen or so pages detailing its behavior can be found on the site.
[[/folder]]

[[folder: Western Animation]]
* Coop accidentally traps Megas in a containment field in an episode of ''{{Megas XLR}}''; he had meant to put up his DeflectorShields, but [[ReverseThePolarity messed with the settings]] beforehand.
* ''WesternAnimation/TheRealGhostbusters'' (and the source movies) has its Ghost Traps and it's Containment Unit, which is just this trope specialized for ghosts. Bad Things happen if you shut off the containment unit. Or if you try to contain something very powerful. Or if Ray sneezes near it. Or...
[[/folder]]

[[folder: Real Life]]
* Modern particle accelerators are actually capable of concentrating destructive amounts of energy in their beams. A failure of the magnetic fields which steer the beam is a very real eventuality, and accelerator designers implement complex machine protection systems that rapidly react to those events in order to avoid damage to the expensive equipment. Simulations show that one beam from the European LHC, at full power, could punch through '''''forty meters of solid copper.'''''[[note]]based on a 86-microsecond exposure[[/note]] Similarly, the Relativistic Heavy-Ion Collider (or RHIC) at Brookhaven National Lab in New York contains redundant magnetic containment for its high-energy ion beams; it also needs gigantic thicknesses of solid marble and heavy metal (lead, iron etc) to 'catch' the beam safely when it's dumped out of the accelerator ring. Both RHIC and the LHC also employ complex electronic and mechanical systems that essentially act as a mechanical 'containment field', a la ''Series/BabylonFive''
** Lead and other heavy metals [[http://www.spectrum.ieee.org/aerospace/astrophysics/cern-to-start-up-the-large-hadron-collider-now-heres-how-it-plans-to-stop-it don't work]] for a beam at the energies the LHC produces. They use a 10-ton rod of graphite and move the beam around so it doesn't melt it.
* Fusion occurs at such high temperatures that, to contain the (generally isotopes of) hydrogen undergoing fusion, you use a magnetic field to keep that superheated fuel away from the walls of the reactor. Fusion reactors have been built and have been run, but the energy required to create, sustain, and contain the reaction has so far been greater than the energy it has been possible to generate (except for fusion ''bombs'', which are obviously impractical for any application that doesn't involve StuffBlowingUp).
** Even smaller devices like fusors found in many colleges, which usually cannot produce net energy, require a massive amount of shielding. In these cases, though, it's less a matter of the released plasma or superheated fuel being an issue, and more a concern about releasing hard X-rays and fast neutrons bouncing around should the lead glass break.
*** However, said magnetic fields not only contain the reaction, they also create the high pressure environment needed for the reaction to occur. Unlike fission, which left to its own will cascade and must be controlled with, yes, control rods, fusion requires a precise environment in term of pressure and temperature. Should the fields fail, then the fusion reaction will simply cease. In other words, if you lose containment, you don't get a boom: the reactor shuts down. Radioactive byproducts of the reaction may still leak out though, depending on how the reactor is engineered. The plasma itself may not instantly cool down either and might pose a threat to nearby objects.
*** Inertial Containment Fusion uses lasers to initiate and contain a fusion reaction. The largest and most powerful lasers in the world, big as football fields, some of them rated in the Terawatt range, are required. Like Magnetic Containment Fusion, failure of the lasers just causes a failure of the fusion reaction, and the reactor shuts down rather than blow up spectacularly.
* Antimatter also needs to be suspended in a magnetic field to prevent it from contacting matter and exploding. Which means that only individual subatomic particles of antimatter can be stored for any length of time, like a positively charged field would contain positrons (anti-electrons) but not anti-protons or neutral atoms of antimatter.
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