Sci-fi space suits tend to have exposed tubes leading from the air tank to the helmet, like twin-hose SCUBA gear. Since space suits are fully pressurized, not just the helmet, these serve no purpose but to be yanked out either to provide a moment of tension or an easy way to end a hand-to-hand fight, depending on if the luckless wearer is a hero or a villain. Even if reconnected, this may lead to an oxygen crisis.
Real space suits have no such dangerously exposed air hoses. Real SCUBA gear has a backup regulator should the first one go bad and the hoses are low pressure. Either sci-fi writers are making commentary on a dystopian future with no safety oversight, they've only ever looked at SCUBA gear (before the 60s that would be everyone) and at other fictional spacesuits that exhibit this trope, or they just need a cheap excuse to add tension.
- Averted in Tintin: Explorers on the Moon, despite how classically retro the spacesuit design looks otherwise. There are no vulnerable oxygen tubes on the exterior of the suit.
- In Yoko Tsuno, the Vineans space suits have very visible air tubes connected to the helmet. Khany's fails in the first story after a rough deceleration. In a later story, Poly yanks one of her own tubes to give air to Yoko.
- In 2001: A Space Odyssey, the space suits had an attached air line. When HAL's pod attacks Frank Poole it rips out his air line, causing him to die of vacuum exposure/lack of air. Watch it here, as Frank frantically tries to re-attach the line.
- In The Empire Strikes Back, an infestation of mynocks required the crew of the Millennium Falcon to venture outside in whatever paltry atmosphere can be found on a large asteroid. They wear face-mounted masks with tubes leading back to oxygen tanks.
- Presumably Han issued Chewie and Leia a set of earplugs and corks before they stepped outside as well.
- Used in Armageddon so that Bruce Willis can subvert his future son-in-law's Heroic Sacrifice by yanking his air line and taking his place.
- Happens in cheapy productions like Missile to the Moon where they just used air force jumpsuits, helmets and oxygen cylinders.
- Star Trek
- Conquest of Space (1955). Combined with the Michelin Man-looking spacesuits to produce Narm when the astronauts are floating about in zero-G.
- Superman II. One of the astronauts has an extended hose leading to the life support system on his moon buggy. Zod kicks him off the Moon's surface, then breaks the hose.
- In the silent movie Woman in the Moon, Professor Mannfeldt goes out in a diving suit to check that the moon has an atmosphere. After successfully lighting a few matches, he takes off his helmet and celebrates (yes, they knew the moon had no atmosphere in 1929, but silent movie actors depended on Facial Dialogue so the audience had to see their face).
- Star Trek: Enterprise features space suits like these, purely for Rule of Drama.
- In "Minefield," Malcolm Reed tries to pull a Heroic Sacrifice by yanking an oxygen tube. Archer puts it back in before yelling at him for it.
- In "Damage," a cracked-out T'Pol, jonesing for some literal rock, falls into a depressurized cargo bay, leading to her air hose coming undone and a frantic struggle to put it back.
- In the final episode of Quark, the ship's computer goes insane and tries to kill Quark by shutting the airlock hatch on his air hose when he's going out for a spacewalk. Fortunately his spacesuit has an emergency supply, giving him enough time to get back on board.
- In The Expanse the pressure-suits worn by the crew of Rocinante feature helmets connected to a "breather" backpack by a corrugated rubber hose. When one character is Almost Out of Oxygen, the medic provides a temporary fix by splicing their hoses together.
- Blake's 7. In "Dawn of the Gods", Vila's air hose breaks off while he's exploring the Eldritch Location that the Liberator has ended up in. After a Commercial Break Cliffhanger Tarrant goes out to look for Vila, but finds he's still alive because the place has a breathable atmosphere.
- The Goodies. Rule of Funny version in "Invasion of the Moon Creatures". Bill has his oxygen cylinder turned up too high, his Fishbowl Helmet inflates like a balloon and he goes flying off the Moon's surface.
- The cover of Robert A. Heinlein's Have Space Suit Will Travel, shown as the page illustration, which was published in 1958. This illustration is also fairly true to the way the suit is described in the book. This trope is, however, extremely averted by other suit designs later in the same book. By comparison with Vegan suits, a Latex Space Suit is bulky.
- The Man Who Rocked the Earth and its sequel The Moon-Maker may be the Trope Maker. The original illustrations included combined shots with the fake Moon landscape and real scuba gear, which was the closest thing available. After all this was one of first relatively "hard" Sci Fi, made in 1915/1916 — they had no Time Travel and all that.
- The Clock Punk spacesuits in The Last Hero. Possibly justified since Leonard's notes reveal that they are using repurposed diving helmets.
- Lampshaded in the Captain Future homage novel Avengers of the Moon, by Allen Steele. Captain Future has to stop a man in a spacesuit from sabotaging his rocketship, and notes that attempting to disconnect the air hose is a standard tactic in hand-to-hand space combat (though he doesn't get the chance).
- The Bio of a Space Tyrant series by Piers Anthony. In "Mercenary", Hope Hubris is commanding a naval Boarding Party and uses a metal needle to puncture the oxygen tube of a Space Pirate.
Now he was in trouble, for I had holed his tube between the tank and the regulatory valve. Oxygen hissed into his suit under unrestrained pressure, bypassing the valve. The outer puncture sealed itself, but not the tube; he was inflating uncomfortably. He had no recourse but to remove his helmet to relieve that pressure, and then I caught his head and jammed my armored finger at a buried nerve complex under the ear, and he was unconscious.
- Space 1889 A variant, perhaps "Space Suits are Hard Hat Diving". The analogy diving-suit space suit is there, and justified, because they are based on hard-hat diving suits. Space suits are based on hard-hat diving suits rather than the not-yet-invented SCUBA Gear
- BattleTech the Elemental Powered Armor was based of a scuba suit developed by Clan Goliath Scorpion, Clan Hell's Horses later redesigned the suit for combat. The elemental armor is capable of fighting in outer space making it useful for boarding enemy ships, and can withstand battlemech grade weapons. It cannot, however, actually function as scuba gear in the game: battle armor is perfectly capable of keeping someone alive underwater as long as the life support system functions and it doesn't get so deep that water pressure risks crushing it, but it's too bulky and difficult to move in to get anywhere in a reasonable amount of time unless it mounts specialized underwater maneuvering equipment.
- In the old Lucasfilm adventure game Zak McKracken and the Alien Mindbenders the lead character builds a spacesuit out of SCUBA gear (the helmet is a fish bowl sealed with tape). Obviously, not the most serious of games.
- In the video game adaptation of Rogue Trooper, some of Rogue's melee animations involve ripping these tubes out of Nort environment suits, exposing them to the toxic air of Nu Earth.
- In Knights of the Old Republic, the spacesuits your party uses for a short spacewalk on the Leviathan's hull are a Palette Swap of an envirosuit used to explore the seafloor of Manaan, complete with a thick tube leading from backpack into helmet.
- In Mass Effect, combat hardsuits can be turned into spacesuits by putting on a helmet connected to life-support via exposed hoses, which never prove to be a problem... until the prologue of Mass Effect 2, where their malfunction costs Shepard's life. From that point on, Shepard's helmet has no visible connection to life-support pack.
- The Dead Space series is usually fairly good about this with the RIG suits free of external hoses and tanks, with two notable exceptions, the Vintage Suit and the EVA suit
- Futurama often uses the classic air tank and hose. In one episode Fry notices that Leela's about to run out of air and switches his tank for hers so she can continue deactivating the Planet Express ship's AI and turn the atmospheric oxygen back on.
- Jackie Chan Adventures does this in the battle with Tso Lan, the Moon Demon. The good guys have the ingredients for the spell to banish the demon again, except one of them is inside Jackie's suit. Tso Lan gloats that Jackie can't remove his helmet without killing himself, to which Jackie replies "Let me air this out" and briefly unhooks his own air hose.
- NASA's Neutral Buoyancy Laboratory (NBL) at Johnson Space Center. Because space suits are conveniently airtight and pressurized, they actually do work underwater just as they do in space, and because of that, NASA actually trains astronauts by using a 40' deep pool within which the suits will feel weightless and movement will be similar to that in space (albiet with much much more drag).
- The Analog Surface Suit◊ (ASS?) used at the Mars Desert Research Station in Utah.
- Mechanical counterpressure suits require this; since the body of the suit is not pressurized, the helmet has to be connected directly to the life support pack.