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Speaker 1: Welcome to brain Stuff from how Stuff Works dot com

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Speaker 1: where smart Happens. Hi, I'm Marshall Brain with today's question,

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Speaker 1: how are people able to breathe inside a submarine? The

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Speaker 1: air we breathe is made up of significant quantities of

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Speaker 1: four gases. There's nitrogen at about oxygen at about argon

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Speaker 1: it maybe one percent, and a little bit of carbon dioxide.

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Speaker 1: Plus there's almost always some amount of water vapor in

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Speaker 1: the air. When we breathe in air, our bodies consume

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Speaker 1: the oxygen and converted to carbon dioxide. Exhaled air, it

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Speaker 1: contains about four to five percent carbon dioxide. Our bodies

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Speaker 1: don't do anything with the nitrogen or the argon. A submarine,

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Speaker 1: or a spaceship for that matter, is a sealed container

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Speaker 1: that holds people in a limited supply of error. There

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Speaker 1: are three things that have to happen in order to

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Speaker 1: keep the air in a submarine breathable. First, the oxygen

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Speaker 1: has to be replenished as it's consumed. If the percentage

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Speaker 1: of oxygen in the air falls too low, a person suffocates. Second,

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Speaker 1: the carbon dioxide must be removed from the air. As

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Speaker 1: the concentration of carbon dioxide rises, it becomes a toxin. Third,

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Speaker 1: the moisture that we exhale in our breath has to

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Speaker 1: be removed. Oxygen is supplied either from pressurized tanks, an

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Speaker 1: oxygen generator which might get oxygen from electrolysis of water,

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Speaker 1: or some sort of oxygen canister. Oxygen is either released

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Speaker 1: continuously by a computerized system, or it's released in batches

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Speaker 1: through the day. Carbon dioxide can be removed from the

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Speaker 1: air chemically using soda lime, which is sodium hydroxide and

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Speaker 1: calcium hydroxide. The carbon dioxide is trapped in the soda

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Speaker 1: line by a chemical reaction and removed from the air.

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Speaker 1: Other similar reactions can accomplish the same thing. The moisture

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Speaker 1: can be moved by a de humidifier or by chemicals.

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Speaker 1: This prevents the moisture from condensing on the walls and

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Speaker 1: equipment inside the ship. Do you have any ideas or

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Speaker 1: suggestions for this podcast? If so, please send me an

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Speaker 1: email at podcast at how stuff works dot com. For

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Speaker 1: more on this and thousands of other topics, go to

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Speaker 1: how stuff works dot com.