# At what level does CO2 make air unbreatheable? **URL:** \ **Category:** Factual Questions\ **Created:** [June 3, 2013, 10:43pm UTC](https://boards.straightdope.com/t/at-what-level-does-co2-make-air-unbreatheable/660074 "2013-06-03T22:43:34Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Try2B\_Comprehensive](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/try2b_comprehensive/32/65_2.png) [@Try2B\_Comprehensive](https://boards.straightdope.com/u/Try2B_Comprehensive)\ **Post date:** [June 3, 2013, 10:43pm UTC](https://boards.straightdope.com/t/at-what-level-does-co2-make-air-unbreatheable/660074/1 "2013-06-03T22:43:34Z")
I have seen this question debated and thought I’d ask the 'dope. Historically, atmospheric CO2 levels were less than 300ppm. These days the level is up above 400ppm. At \_\_\_\_\_\_ppm, people start to complain that the air ‘isn’t fresh’. At \_\_\_\_\_\_ppm people feel drowsy or function poorly. At \_\_\_\_\_\_ppm people start to die. Fill in the blanks! As always, cites appreciated. ---
**Author:** ![DataX](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@DataX](https://boards.straightdope.com/u/DataX)\ **Post date:** [June 3, 2013, 10:57pm UTC](https://boards.straightdope.com/t/at-what-level-does-co2-make-air-unbreatheable/660074/2 "2013-06-03T22:57:12Z")
Here is some info… [http://www.blm.gov/pgdata/etc/medialib/blm/wy/information/NEPA/cfodocs/howell.Par.2800.File.dat/25apxC.pdf](http://www.blm.gov/pgdata/etc/medialib/blm/wy/information/NEPA/cfodocs/howell.Par.2800.File.dat/25apxC.pdf) You probably have a long time to worry, but there are actually answers to these questions, in part, because CO2 is an easy to use measure for indoor air quality (if you think about it - with port ventilation - you’d start to fill up to exhalation standards of CO2). Luckily it seems like you have to go way, way up there to start to effect health. I think OSHA sets a limit of 5,000 and I make no effort whatsoever to ventilate my place (windows are never open) - and I actually have a CO2 meter - and although I can breathe on it and make it go up over 1000, it never goes naturally above 600-700. Of course by long time to worry I mean directly impacting your breathing - I think by the time that happens all the glaciers will be melted and other indirect (if you can call it that) effects will cause massive problems before then. ---
**Author:** ![DataX](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@DataX](https://boards.straightdope.com/u/DataX)\ **Post date:** [June 3, 2013, 11:00pm UTC](https://boards.straightdope.com/t/at-what-level-does-co2-make-air-unbreatheable/660074/3 "2013-06-03T23:00:58Z")
Some wiki info: > [@](#): > > To eliminate most Indoor Air Quality complaints, total indoor carbon dioxide should be reduced to a difference of less than 600 ppm above outdoor levels. NIOSH considers that indoor air concentrations of carbon dioxide that exceed 1,000 ppm are a marker suggesting inadequate ventilation. ASHRAE recommends that carbon dioxide levels not exceed 700 ppm above outdoor ambient levels.[17] The UK standards for schools say that carbon dioxide in all teaching and learning spaces, when measured at seated head height and averaged over the whole day should not exceed 1,500 ppm. The whole day refers to normal school hours (i.e. 9.00am to 3.30pm) and includes unoccupied periods such as lunch breaks. European standards limit carbon dioxide to 3500 ppm. OSHA limits carbon dioxide concentration in the workplace to 5,000 ppm for prolonged periods, and 35,000 ppm for 15 minutes. > **[Indoor air quality](https://en.wikipedia.org/wiki/Indoor_air_quality)** > > Indoor air quality (IAQ) is the air quality within buildings and structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also been linked to sick building syndrome, respiratory issues, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatil... ---
**Author:** ![Try2B\_Comprehensive](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/try2b_comprehensive/32/65_2.png) [@Try2B\_Comprehensive](https://boards.straightdope.com/u/Try2B_Comprehensive)\ **Post date:** [June 3, 2013, 11:34pm UTC](https://boards.straightdope.com/t/at-what-level-does-co2-make-air-unbreatheable/660074/4 "2013-06-03T23:34:27Z")
Thanks. Unless there is some dispute about your numbers, looks like you’ve pulled a one-and-done (in two posts).