Examples of No Biochemical Barriers involving the air people breathe.
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Anime & Manga
- Dragon Ball Z: The planet Namek has a green sky. That alone should point out the differences in composition with Earth's atmosphere, but the humans that visit this planet, and the Namek natives that visit Earth (and the multitude of other aliens from many different worlds that congregate on either planet) have no problem breathing in it or even fighting at full strength. There's also a scene that lampshades this, where Bulma begins analyzing the atmosphere from inside their ship to see if it's breathable — only to look up and see that Gohan and Krillin are already outside.
- In Gargantia on the Verdurous Planet, the Galactic Alliance of Humanity has never found an actual planet to settle on because of this — which is partly why Ledo's rediscovery of Earth is such a big deal. Apparently even their spaceships aren't perfect — when he first wakes up inside a cargo hold and thinks he's in a spaceship, he's surprised to find that it has exactly 1 G.
- Averted in Remina by Junji Ito. The titular planet—actually a planet-sized Eldritch Abomination—is chosen as a destination by a group of human refugees from the doomed Earth, but they crash-land. In order to test if the air is safe to breathe, some of the survivors take the helmet off a man who's already mortally wounded. He immediately melts in the atmosphere of Remina. And that's just the start of the horrors they face on the "planet's" surface.
Comic Books
- In Superman storyline The Untold Story of Argo City, it is unusually averted by an unnamed alien race who cannot survive in the Earth's atmosphere.
- Wonder Woman (1942): Diana and the Holliday Girls visit just about every planet in the solar system, and several beyond, with no protective gear or breathing apparatuses. The only planet they might have had trouble on was Eros, since when Desira (from Venus) asked for their aid she insisted they travel to the planet via astral projection instead of using one of their many available modes of speedy space travel.
Fan Works
- From Bajor to the Black, Part II briefly mentions the Bajoran viewpoint character making a side trip to Starfleet Medical for immunotherapy against Earth pollen after arriving at Starfleet Academy.
- In Maybe the Last Archie Story, Archie's gang find themselves surrounded by weird mists when they arrive at Mad Doctor Doom's Limbo base, and they grow worried about air's toxicity. Nonetheless, they are reassured that all life forms can survive in Limbo.The hatch door opened, retracting into the side of the craft. Some bits of fog-mist came drifting in. Archie shrank back. "That stuff isn't toxic, is it?"
"No," Jan assured him. "Life forms of whatever origin can survive here."
Films ― Animation
- Lampshaded for comedic effect in Toy Story. Woody opens Buzz Lightyear's helmet accidentally, and Buzz starts choking, expecting something deadly. He suddenly realizes...Buzz: The air isn't toxic...? How DARE you open a space ranger's helmet on an uncharted planet! My eyeballs could have been SUCKED from their sockets!
- Even funnier when one considers that he doesn't even have lungs, being a molded hunk of plastic. Of course, he doesn't know that...
- Astro Kid: The planet Willy lands on has an atmosphere breathable for humans.
Films ― Live-Action
- Parodied in Amazon Women on the Moon, in which even the moon has an atmosphere breathable by earthlings.
- Lampshaded and played hilariously straight in Galaxy Quest, when Fred (Tony Shalhoub's character) opens the door of the ship while it's on an alien planet:Guy: Hey, don't open that! It's an alien planet! Is there AIR? You don't know! [holds his breath]
Fred: [sniffing and exhaling a few times] Seems okay. - Independence Day provides a logical, lampshade explanation for this entire trope. When asked what they've learned about the aliens' physiology, Area 51 researcher Dr. Okun explains that, in terms of biological needs, the aliens are actually very close to humans. They breathe oxygen, have similar tolerances to heat, cold, gravity — which, he notes, is probably what attracted them to our planet in the first place. Ammonia-breathing silicon-based life, who can't digest carbon-based life, would have taken just one look at Earth and moved on.
- Most of the aliens in the Men in Black films and the cartoon get along fine without special respirators, although there are exceptions: one species risked premature aging in Earth's atmosphere, while "Atlantis" (actually a sunken space ship) is a posh resort for (salt)water-breathing aliens. When Agent Jay is surprised at the fish-like aliens, Agent Kay lampshades this with "You think all aliens breathe oxygen?"
- Serenity. When the space-suited protagonists land on the planet Miranda, they use a scanner to test the oxygen content and pressure of the atmosphere. When their instruments can't detect anything wrong with it, they take their helmets off.
- Averted in The Space Between Us, where Mars-born Gardner's intolerance towards Earth's atmospheric pressure prevents him from being together with his pen pal from Earth.
- Star Wars: Many different species mingle with humans without respiratory problems. For that matter, it seems likely that various human populations would adapt to the particular atmospheric conditions of their homeworld over the millennia and that they therefore could find the conditions on other worlds tolerable but bothersome. There are some exceptions, though, as a few aliens are shown wearing breathing rigs, and the Expanded Universe adds more.
- It is mentioned that the human Rebels find the Mon Calamari battleships annoyingly warm and humid (Mon Calamari are amphibious and will dry out quickly), but nothing worse than that.
- Gravity gets a similar minor mention, in that humans who grew up on high-gravity worlds tended to be stocky. Otherwise it really doesn't come up.
- The Kel Dor, Jedi Master Plo Koon's species, wear masks and goggles to survive outside their native atmosphere, which consists mostly of helium and an entirely unique substance. Oxygen, nitrogen, and carbon dioxide alike are toxic to them.
- Star Wars Legends adds more — including at least one which doesn't even technically breathe. It also goes a bit more in depth into this with the Gand, which are technically two species. Group one of the Gand must breathe methane or they will enter a coma state. Group two no longer needs to breathe at all. Then there's the case of the Givin, a race that evolved on a planet with a horrific environment, including massive gravity shifts caused by a destabilized moon. The Givin have an exoskeleton that allows them to survive in vacuum for short periods (their planet would have its atmosphere shredded on a regular basis) and an amazing capacity for mathematics that helped them to predict when these gravity shifts would occur.
- The Biochemical Barriers in Avatar apply asymmetrically between humans and Na'vi. Pandora's atmosphere has enough oxygen to be breathable for humans, but it also has hefty amounts of toxic carbon dioxide and hydrogen sulfide, requiring humans to wear full face masks with rebreathers whenever they venture outside. A human caught out without a rebreather risks unconsciousness in seconds and death in minutes. Conversely, The Way of Water shows that Na'vi can manage decently in a human-friendly atmosphere, though they need to inhale from a rebreather of Pandoran air once every ten minutes or so.
Literature
- In Cyteen, the titular planet's atmosphere is chemically fine for humans, but is full of the fibres of local plants, which have an asbestos-like effect on humans. Even the smallest breath of unfiltered air can give you lung cancer years down the line. (In fact, this is how Ariane Emory I was dying before her murder.)
- Hand Waved in Encounter With Tiber with Earth having a "tiber-like" atmosphere.
- In Janitors Of The Post Apocalypse it seems like most species breathe mixtures of nitrogen, oxygen, carbon dioxide and etc but the ratios of each are different. This means that most people on someone else's homeworld or space station can go without their own enclosed air supply, but also need a piece of equipment called a PRA, for humans hung around their necks. These devices locally adjust the air, pumping out oxygen etc, to let their wearers breathe and function comfortably.
- The Kaiju Preservation Society: Kaiju Earth has a much higher level of oxygen in the atmosphere, as well as enough helium that it can be economically extracted for use in KPS airships. Humans experience mild Hyperoxia
until they acclimate to the local conditions. - In the Uplift universe, there are only a few of atmosphere types used by intelligent life: reducing Jupiter-like atmospheres used by hydrogen breathers; nitrogen-rich oxidizing atmospheres used by oxygen-breathers; and rare worlds with fluorine, chlorine, methane, or ammonia-based life. For 2 billion years, the oxygen and hydrogen civilizations have terraformed nearly every potentially-habitable world in the Five Galaxies, making them compatible with each other and seeding them with primitive life-forms. Earth was probably terraformed too, before the Galactics lost track of the planet sometime in the Precambrian. Thus, humans and most oxygen-breathing aliens have little trouble breathing on most oxygen worlds, though there are exceptions.
- The Race from Harry Turtledove's Worldwar series are warm-blooded but reptilian aliens that come from a planet with more land than water, essentially inverting the perception of their planet compared to Earth. They find Earth to mostly be too wet and cold for their liking but chose it over another inhabited planet to invade and colonize because the latter was going through an ice age. When they start to properly settle Earth, they mostly take over the warmer and less-populated Southern Hemisphere with their initial capital on Earth being in Cairo but eventually moving it to Australia because it's the most similar place on Earth to their homeworld. The atmosphere of Earth is otherwise clearly of a comparable if not identical composition to that of Home since they have no trouble breathing on Earth—it was probably part of why they chose it to expand to over any number of uninhabited planets, including others in the Solar System.
Live-Action TV
- BabylonFive zig-zagged this. Four of the five nations that built the station are populated by species who can breathe the same air - humans, Minbari, Centauri, and Narn. Most of the rest of the station's population can too; and nearly all of its volume is filled with an oxygen-nitrogen mix. But there is a section of the station set up with different atmospheres and the Vorlons and a few others are only seen outside of it in enclosed suits. This gets zig-zagged again when we learn that while the humans can't handle the atmosphere in that section without breather masks, some of the other oxygen-breathing aliens can. And it gets zig-zagged one more time when we learn that the Vorlons can handle oxygen-nitrogen air just fine and only use their encounter suits to hide their nature as glowing Energy Beings.
- Babylon Five also had humans walking on the surface of Mars with only breather masks and insulated clothes. This was justified by Mars having been partially terraformed, so that the atmospheric pressure outside was high enough for people to not suffer from the decompression while the air was still not breathable.
- Defiance: Votans are entirely capable of living here in Earth's environment with zero problems regarding air (Liberata are said to breathe nitrogen, yet never need breathing apparatuses to copenote ).
- Earth 2 had the human characters have no problems breathing the air on G889, although they did have problems with water from local some streams & lakes (usually drinking rainwater instead). Justified in the first episode by their having robotic probe data before they left Earth and characters checking the air before leaving their escape pod after the crash landing.
- Farscape usually played this trope straight in all its incarnations but the atmosphere issue is subverted in one episode. In "Relativity" the alien mercenaries employed by Xhalax are used to much less air pressure so they have difficulty keeping up with her.
- Power Rangers as a whole. Not sure whether the ranger's armor acts as a protective gear (surely it does in Power Rangers in Space). But anyway, humans, Human Alien good guys and Dark Specter's forces can breathe on each other's planets. Oh, and apparently you can breathe on the moon, and it has the same gravity as Earth.
- Justified in Stargate SG-1. As Carter points out, you don't make easy travel to planets that are going to kill you if you go there.
- Star Trek is a frequent offender here. Given that the majority of the crews found aboard the ships the various series center around are human, it is reasonable to assume that the air they breathe is adapted to human physiology. Other oxygen-breathing species are almost never shown to find the pressure, temperature or the (presumable) presence of nitrogen and water vapour bothersome. The Benzites and Barzan are the only races that's been described as needing something other than oxygen/nitrogen. It's possible the Breen count too, since those refrigeration suits aren't needed, as well as the Tholians, who naturally live in temperatures of at least 450 Kelvin (177 Celsius). This is explained by an episode of Star Trek: The Next Generation, which explains that most of the species in the Alpha Quadrant did in fact descend from the Precursors, who scattered their genetic code across thousands of worlds, apparently knowing that their own society would inevitably grow proud. This goes some way to explaining why Rubber-Forehead Aliens tolerate nitrogen/oxygen atmospheres, as well as other forms of alien/human... interaction.
- There was a nice moment in a Deep Space 9 episode that seemed to acknowledge this, where Garak, a Cardassian, comments that the environmental settings on the eponymous station, adapted to Bajoran/human norms from their Cardassian originals, are uncomfortable to him — "the temperature is always too cold, the lights are always too bright". Even amongst Trek's often-derided aliens there are still many variations in environmental tolerance. It's regularly pointed out that Cardassians tolerate temperatures too hot for many others, and scenes that take place in Cardassian settings are usually filled with muted colors and lower lighting levels with non-Cardassians require cooling units to survive with their insanity in check.
- There's another mild aversion in Deep Space 9 when Kira and Bashir are discussing the atmospheric requirements for a visiting ambassador.Bashir: Sixty percent nitrogen, ten percent benzene, and the rest hydrogen fluoride, as I recall.
Kira: Well we ran a test in one of the guest quarters. The mixture is so corrosive it dissolved the carpet.
Bashir: Don't look at me. It's what they breathe.
- Averted in Torchwood: Children of Earth, in which the ambassador from the alien species known to earthlings as the 456 requires an atmosphere made of up gases poisonous to humans.
Tabletop RPG
- Zigzaged in classic Traveller Double Adventure 1 Shadows/Annic Nova. One type of special equipment the PCs can buy and use on the adventures is an Atmosphere Tester. One of the Atmosphere Testers is defective and can give false readings.
- In Shadows the PCs explore a pyramid on a planet with a lethal atmosphere. There's a specific location where, if the PCs have a defective Atmosphere Tester, it will malfunction and give a false reading that the air is safe to breathe. If the party believes this and takes off their helmets, they will suffer an immediate Total Party Kill.
- In Annic Nova the PCs must explore an abandoned starship. The adventure urges the game master to pressure the PCs to take off their helmets once they determine the air is safe to breathe. If they do so, when they open a specific door they'll be infected by an airborne disease and quite possibly die.
Video Games
- Zig-zagged in Minecraft: Piglins and Hoglins, the native inhabitants of the Nether, will turn into Zombified Piglins and Zoglins respectively after a few seconds of exposure to the overworld, indicating something about the regular world is toxic to them. This, however, does not apply to the player who enters the Nether, any overworld creature that enters the Nether, or any other creature from the Nether that enter the overworld.
- This happens in The Dig, when the protagonists' NASA spacesuits determine the alien planet's atmosphere to be "at least as breathable as the air in L.A." Why suits that were never intended to encounter any atmosphere have such delicate sensors is not explained. Lowe does bring up the issue of alien microbes, but Brink dismisses this with the argument that they would not be evolved to deal with earthlings. Since they later find alien technology that does work on humans, it's possible he was wrong about that, but none of the protagonists get sick.
- EXTRAPOWER: Attack of Darkforce: Traveling from the Shakun Star to the Earth does not seem to hamper Sharkungo or Forcestar, who are able to breathe and maintain their peak physical fitness just as easily as if they were on their home planet. Even Walhalla, who is only mentioned by name in this game but playable in Star Resistance, is able to function equally on Shakun and on Earth.
- In Final Fantasy IV, the party goes from the surface of the planet to the deep underground — with oceans of lava bright enough to provide ambient light. Then they visit the surface of the Moon, a barren wasteland populated by human-sized versions of (single-cell) eukaryotes and prokaryotes. A case could be made for the latter, but the former should have a noxious atmosphere and should make it impossible for humans to survive in it (to say nothing of the heat and pressure...)
- All the Alien life from the Half-Life series are all able to survive in Earth's atmosphere without issue. This includes creatures from Xen, an alternate dimension where physical constants like gravity only sometime apply.
- Halo: the vast majority of species seen all breathe the same oxygen atmosphere humans do. The one exception is the Grunts, who breathe methane and have to walk around with large breathing tanks strapped to their backs. The Flood is said to alter the atmosphere in some way once it grows large enough, though no one seems to have any problems breathing even in heavily infested areas.
- I Was a Teenage Exocolonist: A generic piece of text from working in the xenobotany lab mentions that humans being able to breathe Vertumna's atmosphere was an unexpected bonus, as the possibility of the planet's life being much more exotic by Earth standards was considered.
- Played straight in Sins of a Solar Empire. Every planet that can be colonized, can be colonized by any player.
- StarCraft II plays this straight during the invasion of Char. Despite the fact that the entire world is a giant volcanic hotspot, the surface consists of compacted ash and solidified lava, and open pits of lava are the equivalent of oceans... humans can still walk around with open helmets. And the rain is apparently perfectly neutral water rather than the expected acid rain. Amusingly, General Warfield had specifically stated earlier that the atmosphere could "burn a man alive". Despite the hellish conditions Char was actually a major colony in the Confederacy due to its large supplies of minerals. The Terrans eventually fought a nuclear war over said minerals, waking several previously dormant volcanoes and producing radiation so dangerous in some areas even fully armored Marines can't survive exposure.
- In Unleash the Light, Steven and Connie can breathe fine on the alien planets without protective gear, even if they're human (or half-human in Steven's case). One of Pearl's quotes when arriving via Warp Pad lampshades this:"Steven, you're in luck! There's a breathable atmosphere here this time!"
Visual Novels
- South Scrimshaw: Averted for human colonists first coming to Aria. While the lifeforms on the planet descended from Earth life and are thus reasonably earthlike in biology, the eons of divergence have resulted in an atmosphere that still requires humans to adjust to breathe comfortably due to the unique microorganisms in the air. New colonists have to spend weeks or even months in a special medical bay where they get treated for constant nausea and get fed locally grown food that will help their gut flora adjust.
Webcomics
- All five species in Runaway to the Stars breathe oxygen, though bug ferrets can tolerate lower oxygen concentrations than most species, with one character recounting a time she won a court case for some humans who worked on a bug ferret habitat without oxygen supplements and suffered long-term cardiac issues as a result.
- Averted in one engagement using untested hardsuits in Schlock Mercenary a squad had their comms jammed and one grunt attempted to take off his helmet to speak audibly.Elf: You know that "external environmental status" light that blinks red sometimes? Well, when you're taking your helmet off it needs to say something a little more direct, like "there's no air out there."
- Non-sci-fi example: The eponymous Tower of Tower of God features Shinsu, a substance that acts as air, water, and weapon depending on concentration, appears even in closed spaces, and generally gets denser the higher one climbs in the Tower. Not only can beings from outside the Tower breathe and drink Shinsu without it disrupting one’s biological functions, they actually have the potential to control it *better* than the natives do, as they don’t require a contract with the Guardians of their respective floors to command it properly. Averted to some extent by the Tower’s native inhabitants—increasing Shinsu pressure as one climbs *does* have the potential to do harm if one’s Shinsu resistance is low, and it serves as an obstacle during a test from Season 1.
- The Floor of Death features another aversion: because the Guardian of that floor is dead, the Shinsu is much thinner and has to be manually manipulated in specific currents to survive. This ends up being a plot point, with the arc villain merged with a fragment of the dead Guardian attempting to siphon the atmosphere away entirely.
- It was also possible for the spell-preserved corpse of a child born within the Tower whose mother escaped the Tower to be resurrected outside it. Said child is the protagonist, Bam.
- None of the main alien species in Trying Human have any trouble breathing Earth's atmosphere and humans likewise seem fine on their ships. Partially justified as like the Star Trek example above, they are said to share a common ancestor.
Web Videos
- Freeman's Mind discusses Xen's surprisingly Earthlike air quality a couple times (see the video games folder for details). Freeman wonders several times how the tiny islands he moves through keep a breathable atmosphere, and comments that it "does taste funny".
Western Animation
- Very few of the aliens in the Ben 10 franchise seem to have problem breathing Earth's atmosphere, including those the titular character transforms into. Water-breathing aliens seem to be the only exception (and any kind of water seems to be OK). As of Ben 10: Omniverse it seems most aliens the titular character transforms into have no trouble surviving in space, so Earth isn't much of a stretch.
- Kid Cosmic: Subverted in "Kid Cosmic and the Local Heroes", where one alien who looks like he's going to be the Monster of the Week ends up suffocating because he can't breathe Earth's atmosphere.
- Steven Universe: Homeworld has an atmosphere where humans Lars, Steven, and Connie are all able to breathe comfortably. This case is especially odd considering that Homeworld's native inhabitants don't need to breathe, and the planet itself is a Shattered World that wouldn't logically have a consistent atmosphere.
- Cybertron in Transformers is shown to be equally hospitable to humans, various aliens, and robots with no need to breathe. This is despite there being no visible atmosphere in most of its depictions.
- Voltron: Legendary Defender: All of the Earth-born characters can easily breathe on alien planets. On the flip side, Krolia, an alien, was able to comfortably live on Earth for at least a year, and had no apparent (physiological) trouble adjusting.
Real Life
- Euryhaline fish can tolerate a wide range of salinities; generally, these fish either are native to estuarine areas where salinity is highly variable (such as the bull shark, which is infamous for travelling hundreds of kilometers up rivers from the sea), or have lifecycles that involve migration between fresh and salty water (and fish in the latter category, such as salmon and eels, can't move directly from salt water to fresh water or vice versa, needing to spend time in brackish waters as their bodies adapt).
- Humans can tolerate all kinds of pressure and gas differences, as long as whatever we're breathing contains an approximate partial pressure of 3.0 psi oxygen and is devoid of active toxins. Heliox (helium-oxygen mix, containing no nitrogen at all) has long been popular with technical divers at extreme depths, as the lack of nitrogen removes one possible avenue for pressure toxicities. On the other hand, oxygen toxicity becomes a real problem at those kinds of depths, so you have to carry multiple mixes, in separate bottles with separate breathing rigs. And only God Himself can save you if you breathe from the green bottle (100% oxygen) at deeper than about 20 feet of salt water.
- Even breathing from liquids isn't impossible if they contain sufficient amounts of oxygen (à la The Abyss), although usually only with mechanical assistance as human lungs don't have the power to move the necessary amount of liquid substance to get enough CO2 out and enough oxygen in, and if you spend too long in the oxygenated fluid, your diaphragm will eventually tear from the strain of having to move the much denser (compared to air) liquid in and out of your lungs.
- For an air pressure example, humans have climbed Mount Everest without oxygen tanks. It is not for everyone and you can get away with being there briefly, but you won't survive if you stay. There is a reason that the atmosphere over 8,000 meters is called "the death zone."
- Approximately 2.6 billion years ago, the oxygen molecule was poisonous to all life on Earth, save a few microorganisms that invented aerobic respiration to use the tiny amounts generated by UV diffraction at the ocean's surface. Then, a new way to extract energy from the environment appeared which we now call "photosynthesis", which transforms carbon dioxide and water into sugar and oxygen. Over a period of roughly 200 million years, the cyanobacteria that produced oxygen became more successful, killing off almost everything that could not adapt to this "toxic waste product"'s effects. Rightfully so, scientists called this event the Oxygen Catastrophe. Nowadays, lots of Earth life depends on oxygen to survive, but anaerobic microbes are still kicking around in sheltered microbiomes — such as your gut. There are also some microbes that cannot do anything useful with oxygen but don't get killed by it.
