# Would I notice if co2 was absent in my immediate vicinity? **URL:** \ **Category:** Factual Questions\ **Created:** [June 23, 2024, 9:02am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221 "2024-06-23T09:02:14Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Saffer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saffer/32/6440_2.png) [@Saffer](https://boards.straightdope.com/u/Saffer)\ **Post date:** [June 23, 2024, 9:02am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/1 "2024-06-23T09:02:14Z")
If I entered a room (large enough for my own co2 emissions to have negligible contribution in the short term) with an otherwise normal atmosphere, except for the complete absence of co2, would I notice anything just from breathing the air? I certainly would notice a significantly higher than normal co2 concentration but I would notice its absence? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 23, 2024, 9:12am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/2 "2024-06-23T09:12:38Z")
I doubt it. > By volume, the dry air in Earth’s atmosphere is about 78.08 percent nitrogen, 20.95 percent oxygen, and 0.93 percent argon. A brew of trace gases accounts for the other approximately 0.04 percent, including the greenhouse gases carbon dioxide, methane, nitrous oxide and ozone. - [SOURCE](https://science.nasa.gov/earth/climate-change/greenhouse-gases/the-atmosphere-getting-a-handle-on-carbon-dioxide/) It’s such a small percent of what you breathe I can’t imagine you’d notice its absence. Plants would notice. You wouldn’t. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 23, 2024, 9:48am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/3 "2024-06-23T09:48:34Z")
Working in the appropriate cursed units. Partial pressure of CO2 in the atmosphere is 0.3mm Hg. The partial pressure of CO2 at the alveoli is critical to the maintenance of blood pH, and sits in the range 35 to 45mm. If it drops below this, respiratory alkalosis begins and things can get grim. Hyperventilation is the well known path to this. Given the atmospheric concentration is less than 1% of the alveolar value, a zero partial pressure of CO2 in the air might have a real but likely near imperceptible effect on blood pH. You would be hard pressed to see the difference it in the noise. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 23, 2024, 9:50am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/4 "2024-06-23T09:50:38Z")
Does a person even need an intake of CO2 since they exhale CO2? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [June 23, 2024, 11:32am UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/5 "2024-06-23T11:32:51Z")
The air would feel very fresh, I suppose. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [June 23, 2024, 12:02pm UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/6 "2024-06-23T12:02:33Z")
You are not suppose to inhale pure oxygen > **[UCLA Study Reveals Why Bad Things Happen Inside the Brain When We Inhale Pure...](https://www.uclahealth.org/news/release/ucla-study-reveals-why-bad-things-happen-inside-the-brain-when-we-inhale-pure-oxygen)** > > It's a scenario straight out of "Grey's Anatomy"— a paramedic or doctor plops a mask over the face of a person struggling to breathe and begins dispensing pure oxygen.  Yet growing research suggests that inhaling straight oxygen can actually... > **[Oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity)** > > Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen (O2) at increased partial pressures. Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lungs, and eyes. Historically, the central nervous system condition was called the Paul Bert effect, and the pulmonary condition the Lorrain Smith effect, after the researchers who pioneered the discoveries and descriptions in the late 19th century. Oxygen... but I don’t see any regulations about carbon dioxide except that it is considered a contaminant in breathing gas: > **[Regulations%20Booklet.pdf](https://www.factair.co.uk/_webedit/uploaded-files/All%20Files/Regulations%20Booklet.pdf)** > > 940.96 KB ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 23, 2024, 12:29pm UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/7 "2024-06-23T12:29:51Z")
Been there, done that. The community garden that my mom is involved with has a passive greenhouse on site. It does a great job of managing the temperature year-round, but carbon dioxide levels are indistinguishable from zero, with the detectors they use (they’ve put rotting compost in to try to bring it up, but the plants grab up the gas as quickly as it’s produced). Ironically, one of the sponsors of the project was a local microbrewery, and if they’d sited it at the brewery, they’d have no problem providing plenty of carbon dioxide. As a human, I didn’t notice any difference, beyond smelling the growing herbs. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [June 23, 2024, 1:42pm UTC](https://boards.straightdope.com/t/would-i-notice-if-co2-was-absent-in-my-immediate-vicinity/1003221/8 "2024-06-23T13:42:01Z")
> [@Whack-a-Mole](#): > > Does a person even need an intake of CO2 since they exhale CO2? No. The trick is that it is all an equilibrium system. The partial pressure of CO2 at the alveoli is so much larger than the partial pressure of CO2 in the air that the travel of CO2 is essentially all in one direction. But the molecules rattling about at the interface don’t know where they came from. They just rattle about, and on average the ratting about takes the CO2 out of the bloodstream and is exhaled. This gives a clue about what happens when the CO2 concentration in the air increases. If the concentration in the air matches or exceeds that seen at interface in the alveoli, there will be no net transport of CO2 out of the blood. Which is why 3% CO2 in the air is generally fatal, and 1% will result of mass evacuation on detection. Perhaps the well known one is the idea of getting someone to breath in and out into a paper bag. The idea being to deliberately increase blood CO2 - as an antidote to respiratory alkalosis due to hyperventilation after (or during) a severe anxiety or panic attack. Not clear how much the CO2 really helps, or whether the benefit is more about focussing on the breathing and generally getting something else to worry about.