Almost Out of Oxygen

""Your air supply is running out!""

- Sparks, Lego Rock Raiders

Dammit! The Spacecraft is damaged! The Submarine can't return to the surface! We're enclosed underneath a million tons of rocks! The oxygen will only last us 110 minutes!

Always Close to resolving their unfortunate predicament (the climax) the crew is Almost Out of Oxygen. Involves a type of Magic Countdown to increase tension.

Only Hollywood Science actually has people die from the lack of oxygen when in an airtight space. In shows where the science is harder, the protagonists are threatened by carbon dioxide poisoning instead. Of course, from the characters' perspectives, this generally doesn't make any difference.

It is also very possible to die from hypoxia per se. Compare DrowningPit which is a deliberate Death Trap variant of this. May lead to a Cold Equation.

Anime

 * Planetes: Used rather tragically in the climax. Cheerful Idealist Ai Tanabe is trying to make it to shelter across the lunar desert while carrying an injured companion  Ai refuses to leave her behind, even though the extra weight is slowing her down and burning her oxygen faster. She doesn't make it to shelter before her air runs out, and is faced with the choice of taking the other person's oxygen tank so that she will survive, or letting them both die.
 * This scene plays differently in the manga—unlike the anime that loves to overplay the emotional side of things and add melodramatic episodes, it's much more casual and matter-of-factly. First, it weren't Tanabe and Claire (who is an anime-only character), it were Hachimaki and his co-trainee for the Jupiter mission, Leonov, and there wasn't any animosity involved; and second, long before they run up of their oxygen they are saved by Tanabe and Yuri.
 * Katekyo Hitman Reborn: Tsuna was
 * On Speed Racer, button "F" on the Mach 5's steering wheel engages the car's "submarine" mode. The air tank on board the car only has enough oxygen for half an hour, though. At the end of one 2-parter, Speed and Trixie are trapped in the Mach 5 underwater when its oxygen tank is nearly empty. They're seen gasping for air and everything.

Comic Books

 * Tintin: Because of stowaways both intentional and accidental, this becomes a problem at the very end of Destination Moon.
 * One issue of Judge Dredd that took place on a moon colony (where oxygen was apparently a utility you had to pay for), the criminals escaped the Judges, only to learn that they were behind on their oxygen bill, resulting in the atmosphere of their hideout being vented. They all suffocated trying to escape.

Film

 * The Abyss. Everyone gets to breathe a sigh of relief after, but then suddenly, an oxygen check is asked for and the guy only has 5 minutes of oxygen left, and it took much longer than that to get down there...
 * In Red Planet, Earth itself has run out of oxygen, so the main characters have to send oxygen producing algae to mars to create livable air. The main characters start to run out of oxygen in their habitation module, when one of the characters removes his helmet to find that Mars somehow has breathable air.
 * 12th Man: One man, two hours of oxygen, one escape pod, and 11 Ax Crazy psychopaths who want it as much as he does.
 * In Apollo 13, a central plot point is having them MacGyvering carbon dioxide filters from their command module into the ventilation system of the LEM. The filters and the ventilation system socket are different shapes. So the crew and Mission Control have to figure out how to fit a square peg in a round hole.
 * Oxygen was also a critical problem in the opening minutes of the crisis, but not for the traditional reason. The dwindling liquid-oxygen supplies were also used to run the fuel cells that provided power (and drinking water) for the command/service module. They had plenty of breathing oxygen in the lunar module's tanks - but if they ran out of power before they could get the LM up and running...
 * Averted in Event Horizon where it's not the lack of air that threatens the crew but the rising CO2 levels due to running out of usable air filters. Well, that and.
 * In Space Camp, a shuttle full of teenagers accidentally gets launched during an engine test without enough oxygen for an actual mission.
 * In Battle for Terra, Jim runs out of Oxygen on his spacesuit, and the other protagonists have to synthesize it for him. Later in the movie, Jim has to choose between pumping Oxygen into a room to save his brother, or to pump the native air into a room to save the female protagonist. He takes a third option. Another example in the movie is when the terraformer activates, and it is stated that Terra will run out of Native Air, killing all native species, unless it is destroyed; however, the humans are running out of oxygen. The situation is resolved with Jim's heroic sacrifice, and a compromise between species.
 * The upcoming Gravity seems to be made of this trope.

Literature

 * The second Artemis Fowl book is loaded down with action tropes, and accordingly applies this one while the imperiled character is surrounded by fiery plasma. However, it also mentions that it's rising carbon dioxide levels that's the danger.
 * Under the Dome by Stephen King provides an Earth based example:
 * The Space Trilogy: In the first book, Ransom, Weston, and Devine have only ninety days to get home with a limited supply of oxygen. They only barely make it.
 * In Twenty Thousand Leagues Under the Sea, the Nautilus is trapped under the Antarctic ice. Oxygen is not a problem, due to the Nautilus having plenty of electricity and water around, but without caustic potash to bind the CO2 the heroes are screwed anyway.
 * In the first Starbridge novel, the three main characters are on a small spaceship when most of the oxygen-generating plants up and die. As they are too far out now to either reach their destination or turn back, their only hope is to search for an oxygen-bearing planet to harvest some plants for oxygen production before it's too late.

Live-Action TV
"River: You're afraid we're going to run out of air. That we'll die gasping. But we won't. That's not going to happen. We'll freeze to death first."
 * The three part pilot for Stargate Universe is entitled "Air", after the first struggle they face on board the ship. There are major leaks spilling the air out into space which had to be fixed, one in a seemingly unreachable spot. Once they fix that, they find out the carbon dioxide scrubbers aren't working. D'oh.
 * Subverted in the Firefly episode "Out of Gas":

"Paris: When we first met you didn't have a very high opinion of me. Torres: That's putting it mildly. I thought you were an arrogant, self-absorbed pig. Paris: Flattery won't get you any more oxygen."
 * Bones has an episode where Brennan and Hodgins are buried alive with a limited amount of air. They manage to juryrig a carbon dioxide filter out of commonly available equipment.
 * Not to mention puncturing the tires to release more oxygen.
 * In the Red Dwarf episode Quarantine, the quarantined crew members are sentenced to two hours WOO (With Out Oxygen). It actually implies the carbon dioxide problem; all that's said is that the air will 'become unbreathable'..
 * Doctor Who: In "Smith and Jones" a hospital gets sucked onto a moon—thankfully the air's kept in a bubble around the building. Of course, they've still got limited oxygen...
 * In the Star Trek: Enterprise episode "Shuttlepod One", Trip Tucker and Malcolm Reed find debris of what they wrongly assume to be the crashed starship Enterprise on an asteroid. Because of the limited oxygen supply and reach of the shuttlepod, they believe they're stranded in space and try to face their oncoming deaths in their own conflicting ways.
 * In Star Trek: Voyager's "Day of Honor", Tom and B'Elanna are adrift in spacesuits after their shuttle is destroyed. Turbulence soon punctures one oxygen tank, forcing them to share. By the dialogue, the other oxygen tank should have been enough to provide for both of them for a very long time, but it was also (albeit less critically) damaged by the same turbulence.

Theatre

 * Aida: A lethal version occurs in the finale between, set to the reprise of "Enchantment Passing Through."

Webcomics

 * In The Lydian Option, the Tha'Latta use venting the atmosphere as a method of quelling prison riots in their asteroid prison - killing all of the prisoners inside. The human prisoners are forced to seek an escape facing an imminent venting.

Western Animation

 * Futurama, "Love and Rockets": the Planet Express ship computer (which has developed a crush on Bender and gone completely insane) cuts off the oxygen supply, so Leela and Fry have to wear spacesuits while they try to switch it off.

Video Games

 * In Pikmin, when Captain Olimar crash-lands on a planet that totally isn't Earth, he has thirty days to repair his ship before he runs out of breathable air. Inverted in that in Olimar's case, oxygen is the poison that's going to kill him.
 * In Lego Rock Raiders, most of the later caverns have a limited oxygen supply, and Sparks will continually warn: "Your air supply is running out!" until you build enough Support Stations to maintain the oxygen levels. The actual Almost Out of Oxygen point is when he starts saying, "Your air supply is running low." and you can hear a heartbeat over the background music.
 * As if Spelunker wasn't Nintendo Hard enough, its levels also ran on a timer—the eponymous spelunker's air supply. There are some powerups to refill the air meter, but good luck getting to them.
 * In the Sonic the Hedgehog series, you can only stay underwater for a limited amount of time and when you're Almost Out of Oxygen, the Magic Countdown appears and the music starts playing.

Real Life

 * The above-mentioned Apollo 13 is of course based on the story of the real mission.
 * The sinking of the Kursk. In a tragically ironic twist, it was the emergency oxygen generators reacting violently with water leaking into the sub that killed off the final survivors.