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Comment by groby_b | Hacker News Reader

800ppm is a fairly typical value for indoor CO2 and not really that shocking.

Fun fact: We've known since ~1850[1] that we should probably stay below 1000ppm for indoors, but we based the measure back then on body odor :) (It still bugs me that oddly cognitive impairment starts at the same point a body-odor measure from the 1800s put CO2 levels, and I keep wondering if we're seeing confirmation bias in action)

In general, where you end up is based on airflow. To get below 800ppm, you'll probably need to increase outside ventilation to >10dm^3/s.

[1] von Pettenkofer, "Ueber den Luftwechsel in Wohngebaeuden"

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Fascinating. If you were a fan of evolutionary origin stories, you could easily imagine that the negative association with body odor is an evolved "canary in the coal mine" mechanism. That is, once you start being irritated by your cave-mates BO, it's time to step outside for some fresh air (before you are asphyxiated).

That said, I doubt humanity spent enough time in caves or other restricted airflow environments for such a response to evolve...

Additionally, to support the idea that we evolved to detect and dislike body odor, you'd have to make sure that humans even have this trait. Too many evolutionary just-so stories generate hypotheses from limited cultural observations.

This article about one of the few remaining hunter-gatherer people left, the Hadza, might lead you to question the idea that humans have a "dislike body odor" trait:

> While Hadza have a word for body odor, the men tell me that they prefer their women not to bathe—the longer they go between baths, they say, the more attractive they are. Nduku, my Hadza language teacher, said she sometimes waits months between baths, though she can't understand why her husband wants her that way.

https://www.nationalgeographic.com/magazine/2009/12/hadza/

And this despite the theory that hunter-gatherers are probably even better at smelling than we are: https://www.sciencedaily.com/releases/2018/01/180118142744.h...

A larger issue is Hadza like most hunter gatherers don’t live in caves, which are fairly rare in most parts of the world.

The idea of ‘cave man’ is sampling bias because natural caves preserve ancient artifacts which tend to disappear in the open.

I would be interested to see if increased levels of CO2 alter our perceptions of smells/odors. It may become more unpleasant to encourage us to vacate the poorly ventilated area.

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