# Why is ones breath always warm?

**URL:** <https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246>\
**Category:** Factual Questions\
**Created:** [January 16, 2001, 12:29am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246 "2001-01-16T00:29:53Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![elite](https://avatars.discourse-cdn.com/v4/letter/e/6f9a4e/32.png) [@elite](https://boards.straightdope.com/u/elite)\
**Post date:** [January 16, 2001, 12:29am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246/1 "2001-01-16T00:29:53Z")

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How is it possible that air that is breathed in is always exhaled at a warm temperature? For example, if one breathes sub zero temperature air, it comes out warm. How is it that it is warmed so quickly? After all it only stays at most a few seconds in the lungs!

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**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\
**Post date:** [January 16, 2001, 12:43am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246/2 "2001-01-16T00:43:03Z")

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1. The air you exhale is a mix of your last breath and the air from earlier breaths still in your lungs, so some of it stays in longer than the length of one inhale/exhale cycle.

2. A breath of air, while possibly very cold, doesn’t contain much heat (or rather, absence of heat), since it doesn’t have much mass. It takes very few calories to heat a breath of air from very cold to body temperature.

Arjuna34

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**Author:** ![WillGolfForFood](https://avatars.discourse-cdn.com/v4/letter/w/82dd89/32.png) [@WillGolfForFood](https://boards.straightdope.com/u/WillGolfForFood)\
**Post date:** [January 16, 2001, 12:44am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246/3 "2001-01-16T00:44:57Z")

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1. Your interior body is something like 98 degrees.

2. Your lungs aren’t just one giant flat bellows - they’ve got a tremendous surface area to them. After all, the air you breathe has to come in contact with your lung tissue in order for that tissue to be able to extract the oxygen from it. And that contact helps transfer warmth from your lung tissue to the air you’re breathing.

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**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\
**Post date:** [January 16, 2001, 1:26am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246/4 "2001-01-16T01:26:30Z")

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In addition to what Arjuna and WGfF said, your exhaled breath also contains water vapor and CO[sub]2[/sub] that you didn’t breathe in. These gases are at about the same temp as the lungs (37[sup]o[/sup] C).

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**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\
**Post date:** [January 16, 2001, 1:28am UTC](https://boards.straightdope.com/t/why-is-ones-breath-always-warm/50246/5 "2001-01-16T01:28:57Z")

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One function of breathing is to take heat from the body, thus it’s warm.

Pee is always warm too & also serves that function which seems not to apply to what’s said.