Editing Carbon dioxide (section)

=== Toxicity ===
{{See also|Carbon dioxide poisoning}}
[[File:Main symptoms of carbon dioxide toxicity.svg|thumb|upright=1.15|left|Symptoms of carbon dioxide toxicity, by increasing [[volume percent]] in air<ref name="friedman">{{cite web |title=Toxicity of Carbon Dioxide Gas Exposure, {{CO2}} Poisoning Symptoms, Carbon Dioxide Exposure Limits, and Links to Toxic Gas Testing Procedures |url=http://www.inspect-ny.com/hazmat/CO2gashaz.htm |archive-url=https://web.archive.org/web/20090928073740/http://www.inspect-ny.com/hazmat/CO2gashaz.htm |archive-date=28 September 2009 |work=InspectAPedia |vauthors=Friedman D}}</ref>]]

Carbon dioxide content in fresh air (averaged between sea-level and 10&nbsp;kPa level, i.e., about {{cvt|30|km}} altitude) varies between 0.036% (360&nbsp;ppm) and 0.041% (412&nbsp;ppm), depending on the location.<ref>{{cite web |title=CarbonTracker CT2011_oi (Graphical map of {{CO2}}) |url=http://www.esrl.noaa.gov/gmd/ccgg/carbontracker/ |url-status=live |archive-url=https://web.archive.org/web/20210213080315/https://www.esrl.noaa.gov/gmd/ccgg/carbontracker/ |archive-date=13 February 2021 |access-date=20 April 2007 |work=esrl.noaa.gov}}</ref>

In humans, exposure to {{CO2}} at concentrations greater than 5% causes the development of [[hypercapnia]] and [[respiratory acidosis]].<ref name="Permentier-2017">{{Cite journal |last1=Permentier |first1=Kris |last2=Vercammen |first2=Steven |last3=Soetaert |first3=Sylvia |last4=Schellemans |first4=Christian |date=2017-04-04 |title=Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the emergency department |journal=International Journal of Emergency Medicine |volume=10 |issue=1 |page=14 |doi=10.1186/s12245-017-0142-y |issn=1865-1372 |pmc=5380556 |pmid=28378268 |doi-access=free}}[[File:CC-BY_icon.svg|50x50px]] Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]]</ref> Concentrations of 7% to 10% (70,000 to 100,000&nbsp;ppm) may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.<ref name="USEPA">{{cite news |title=Carbon Dioxide as a Fire Suppressant: Examining the Risks |publisher=U.S. Environmental Protection Agency |url=http://www.epa.gov/ozone/snap/fire/co2/co2report.html |archive-url=https://web.archive.org/web/20151002093443/http://www.epa.gov/ozone/snap/fire/co2/co2report.html |archive-date=2 October 2015}}</ref> Concentrations of more than 10% may cause convulsions, coma, and death. {{CO2}} levels of more than 30% act rapidly leading to loss of consciousness in seconds.<ref name="Permentier-2017" />

Because it is heavier than air, in locations where the gas seeps from the ground (due to sub-surface volcanic or geothermal activity) in relatively high concentrations, without the dispersing effects of wind, it can collect in sheltered/pocketed locations below average ground level, causing animals located therein to be suffocated. Carrion feeders attracted to the carcasses are then also killed. Children have been killed in the same way near the city of [[Goma]] by {{CO2}} emissions from the nearby volcano [[Mount Nyiragongo]].<ref>{{cite web |date=1 November 2005 |title=Volcano Under the City |url=https://www.pbs.org/wgbh/nova/transcripts/3215_volcanoc.html |archive-url=https://web.archive.org/web/20110405155241/http://www.pbs.org/wgbh/nova/transcripts/3215_volcanoc.html |archive-date=5 April 2011 |work=A NOVA Production by Bonne Pioche and Greenspace for WGBH/Boston |publisher=Public Broadcasting System}}.</ref> The [[Swahili language|Swahili]] term for this phenomenon is {{lang|sw|[[mazuku]]}}.

[[File:Apollo13 apparatus.jpg|thumb|Rising levels of {{CO2}} threatened the [[Apollo 13]] astronauts, who had to adapt cartridges from the command module to supply the [[carbon dioxide scrubber]] in the [[Apollo Lunar Module]], which they used as a lifeboat.]]
Adaptation to increased concentrations of {{CO2}} occurs in humans, including [[Respiratory adaptation|modified breathing]] and kidney bicarbonate production, in order to balance the effects of blood acidification ([[acidosis]]). Several studies suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a [[submarine]]) since the adaptation is physiological and reversible, as deterioration in performance or in normal physical activity does not happen at this level of exposure for five days.<ref>{{cite report |url=http://archive.rubicon-foundation.org/6045 |title=Carbon Dioxide Tolerance Studies |id=SAM-TR-67-77 |access-date=2 May 2008 |archive-url=https://web.archive.org/web/20080509072828/http://archive.rubicon-foundation.org/6045 |archive-date=9 May 2008 |url-status=usurped |vauthors=Glatte Jr HA, Motsay GJ, Welch BE |year=1967 |series=Brooks AFB, TX School of Aerospace Medicine Technical Report}}</ref><ref>{{cite report |url=http://archive.rubicon-foundation.org/3861 |title=Carbon Dioxide Tolerance and Toxicity |publisher=Environmental Biomedical Stress Data Center, Institute for Environmental Medicine, University of Pennsylvania Medical Center |id=No. 2-71 |access-date=2 May 2008 |archive-url=https://web.archive.org/web/20110724044527/http://archive.rubicon-foundation.org/3861 |archive-date=24 July 2011 |url-status=usurped |vauthors=Lambertsen CJ |year=1971 |series=IFEM Report}}</ref> Yet, other studies show a decrease in cognitive function even at much lower levels.<ref name="pollutant2012">{{cite journal |vauthors=Satish U, Mendell MJ, Shekhar K, Hotchi T, Sullivan D, Streufert S, Fisk WJ |date=December 2012 |title=Is {{CO2}} an indoor pollutant? Direct effects of low-to-moderate {{CO2}} concentrations on human decision-making performance |url=http://ehp.niehs.nih.gov/wp-content/uploads/2012/09/ehp.1104789.pdf |url-status=dead |journal=Environmental Health Perspectives |volume=120 |issue=12 |pages=1671–1677 |doi=10.1289/ehp.1104789 |pmc=3548274 |pmid=23008272 |archive-url=https://web.archive.org/web/20160305212909/http://ehp.niehs.nih.gov/wp-content/uploads/2012/09/ehp.1104789.pdf |archive-date=5 March 2016 |access-date=11 December 2014}}</ref><ref name="scores2016">{{cite journal |author-link=Joseph G. Allen |vauthors=Allen JG, MacNaughton P, Satish U, Santanam S, Vallarino J, Spengler JD |date=June 2016 |title=Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments |journal=Environmental Health Perspectives |volume=124 |issue=6 |pages=805–812 |doi=10.1289/ehp.1510037 |pmc=4892924 |pmid=26502459|bibcode=2016EnvHP.124..805A }}</ref> Also, with ongoing respiratory [[acidosis]], adaptation or compensatory mechanisms will be unable to reverse the condition.

==== Below 1% ====
There are few studies of the health effects of long-term continuous {{CO2}} exposure on humans and animals at levels below 1%. Occupational {{CO2}} exposure limits have been set in the United States at 0.5% (5000&nbsp;ppm) for an eight-hour period.<ref name="inspectpedia">{{cite web |title=Exposure Limits for Carbon Dioxide Gas – {{CO2}} Limits |url=http://www.inspectapedia.com/hazmat/CO2_Exposure_Limits.htm |url-status=live |archive-url=https://web.archive.org/web/20180916235612/https://inspectapedia.com/hazmat/CO2_Exposure_Limits.htm |archive-date=16 September 2018 |access-date=19 October 2014 |publisher=InspectAPedia.com}}</ref> At this {{CO2}} concentration, [[International Space Station]] crew experienced headaches, lethargy, mental slowness, emotional irritation, and sleep disruption.<ref>{{cite report |url=http://ston.jsc.nasa.gov/collections/trs/_techrep/TP-2010-216126.pdf |title=In-Flight Carbon Dioxide Exposures and Related Symptoms: Associations, Susceptibility and Operational Implications |id=TP–2010–216126 |access-date=26 August 2014 |archive-url=https://web.archive.org/web/20110627061502/http://ston.jsc.nasa.gov/collections/TRS/_techrep/TP-2010-216126.pdf |archive-date=27 June 2011 |url-status=dead |vauthors=Law J, Watkins S, Alexander D |year=2010 |series=NASA Technical Report}}</ref> Studies in animals at 0.5% {{CO2}} have demonstrated kidney calcification and bone loss after eight weeks of exposure.<ref>{{cite journal |vauthors=Schaefer KE, Douglas WH, Messier AA, Shea ML, Gohman PA |year=1979 |title=Effect of prolonged exposure to 0.5% {{CO2}} on kidney calcification and ultrastructure of lungs |url=http://handle.dtic.mil/100.2/ADA075625 |url-status=dead |journal=Undersea Biomedical Research |volume=6 |issue=Suppl |pages=S155–S161 |pmid=505623 |archive-url=https://web.archive.org/web/20141019131035/http://handle.dtic.mil/100.2/ADA075625 |archive-date=19 October 2014 |access-date=19 October 2014}}</ref> A study of humans exposed in 2.5 hour sessions demonstrated significant negative effects on cognitive abilities at concentrations as low as 0.1% (1000{{nbsp}}ppm) {{CO2}} likely due to {{CO2}} induced increases in cerebral blood flow.<ref name="pollutant2012" /> Another study observed a decline in basic activity level and information usage at 1000&nbsp;ppm, when compared to 500&nbsp;ppm.<ref name="scores2016" />

However a review of the literature found that a reliable subset of studies on the phenomenon of carbon dioxide induced cognitive impairment to only show a small effect on high-level decision making (for concentrations below 5000 ppm). Most of the studies were confounded by inadequate study designs, environmental comfort, uncertainties in exposure doses and differing cognitive assessments used.<ref>{{cite journal |vauthors=Du B, Tandoc MC, Mack ML, Siegel JA |date=November 2020 |title=Indoor {{CO2}} concentrations and cognitive function: A critical review |journal=Indoor Air |volume=30 |issue=6 |pages=1067–1082 |doi=10.1111/ina.12706 |pmid=32557862 |bibcode=2020InAir..30.1067D |s2cid=219915861|doi-access=free}}</ref> Similarly a study on the effects of the concentration of {{CO2}} in motorcycle helmets has been criticized for having dubious methodology in not noting the self-reports of motorcycle riders and taking measurements using mannequins. Further when normal motorcycle conditions were achieved (such as highway or city speeds) or the visor was raised the concentration of {{CO2}} declined to safe levels (0.2%).<ref>{{Cite web |date=4 June 2019 |title=Ask the doc: Does my helmet make me stupid? - RevZilla |url=https://www.revzilla.com/common-tread/ask-the-doc-does-my-helmet-make-me-stupid |url-status=live |archive-url=https://web.archive.org/web/20210522081133/https://www.revzilla.com/common-tread/ask-the-doc-does-my-helmet-make-me-stupid |archive-date=22 May 2021 |access-date=2021-05-22 |website=www.revzilla.com |vauthors=Kaplan L}}</ref><ref>{{cite journal |vauthors=Brühwiler PA, Stämpfli R, Huber R, Camenzind M |date=September 2005 |title={{CO2}} and {{O2|nolink=no}} concentrations in integral motorcycle helmets |journal=Applied Ergonomics |volume=36 |issue=5 |pages=625–633 |doi=10.1016/j.apergo.2005.01.018 |pmid=15893291}}</ref>

{| class="wikitable"
|+ Typical {{CO2}} concentration effects
! Concentration !! Note
|-
| 280 ppm || Pre-industrial levels
|-
| 421 ppm || Current (May 2022) levels
|-
| ~1121 ppm || [[ASHRAE]] recommendation for indoor air<ref>{{Cite web |date=2018 |title=Ventilation for Acceptable Indoor Air Quality |url=https://www.ashrae.org/File%20Library/Technical%20Resources/Standards%20and%20Guidelines/Standards%20Addenda/62.1-2016/62_1_2016_d_20180302.pdf |url-status=live |access-date=2023-08-10 |issn=1041-2336 |archive-url=https://web.archive.org/web/20221026132957/https://www.ashrae.org/File%20Library/Technical%20Resources/Standards%20and%20Guidelines/Standards%20Addenda/62.1-2016/62_1_2016_d_20180302.pdf |archive-date=Oct 26, 2022}}</ref>
|-
| 5,000 ppm || USA 8h exposure limit<ref name="inspectpedia"/>
|-
| 10,000 ppm || Cognitive impairment, Canada's long term exposure limit<ref name="friedman" />
|-
| 10,000-20,000 ppm || Drowsiness<ref name="USEPA" />
|-
| 20,000-50,000 ppm || Headaches, sleepiness; poor concentration, loss of attention, slight nausea also possible<ref name="inspectpedia" />
|}

==== Ventilation ====
[[File:CO2Mini monitor TFA Dostmann.jpg|thumb|A [[carbon dioxide sensor]] that measures {{CO2}} concentration using a [[nondispersive infrared sensor]]]]
Poor ventilation is one of the main causes of excessive {{CO2}} concentrations in closed spaces, leading to poor [[indoor air quality]]. Carbon dioxide differential above outdoor concentrations at steady state conditions (when the occupancy and ventilation system operation are sufficiently long that {{CO2}} concentration has stabilized) are sometimes used to estimate ventilation rates per person.<ref>{{Cite web |title=Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation |url=https://www.astm.org/d6245-98.html |access-date=2024-06-12 |website=www.astm.org |language=en}}</ref> Higher {{CO2}} concentrations are associated with occupant health, comfort and performance degradation.<ref>{{cite journal |vauthors=Allen JG, MacNaughton P, Satish U, Santanam S, Vallarino J, Spengler JD |date=June 2016 |title=Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments |journal=Environmental Health Perspectives |volume=124 |issue=6 |pages=805–812 |doi=10.1289/ehp.1510037 |pmc=4892924 |pmid=26502459|bibcode=2016EnvHP.124..805A }}</ref><ref>{{Cite web |date=26 October 2015 |title=Exclusive: Elevated {{CO2}} Levels Directly Affect Human Cognition, New Harvard Study Shows |url=https://thinkprogress.org/exclusive-elevated-co2-levels-directly-affect-human-cognition-new-harvard-study-shows-2748e7378941/ |url-status=live |archive-url=https://web.archive.org/web/20191009092140/https://thinkprogress.org/exclusive-elevated-co2-levels-directly-affect-human-cognition-new-harvard-study-shows-2748e7378941/ |archive-date=9 October 2019 |access-date=14 October 2019 |website=ThinkProgress |vauthors=Romm J}}</ref> [[ASHRAE]] Standard 62.1–2007 ventilation rates may result in indoor concentrations up to 2,100&nbsp;ppm above ambient outdoor conditions. Thus if the outdoor concentration is 400&nbsp;ppm, indoor concentrations may reach 2,500&nbsp;ppm with ventilation rates that meet this industry consensus standard. Concentrations in poorly ventilated spaces can be found even higher than this (range of 3,000 or 4,000&nbsp;ppm).

Miners, who are particularly vulnerable to gas exposure due to insufficient ventilation, referred to mixtures of carbon dioxide and nitrogen as "[[blackdamp]]", "choke damp" or "stythe". Before more effective technologies were developed, [[miners]] would frequently monitor for dangerous levels of blackdamp and other gases in mine shafts by bringing a caged [[Domestic Canary|canary]] with them as they worked. The canary is more sensitive to asphyxiant gases than humans, and as it became unconscious would stop singing and fall off its perch. The [[Davy lamp]] could also detect high levels of blackdamp (which sinks, and collects near the floor) by burning less brightly, while [[methane]], another suffocating gas and explosion risk, would make the lamp burn more brightly.

In February 2020, three people died from suffocation at a party in Moscow when dry ice (frozen {{CO2}}) was added to a swimming pool to cool it down.<ref>{{cite web |date=29 February 2020 |title=Three die in dry-ice incident at Moscow pool party |url=https://www.bbc.co.uk/news/world-europe-51680049 |archive-url=https://web.archive.org/web/20200229151448/https://www.bbc.co.uk/news/world-europe-51680049 |archive-date=29 February 2020 |work=BBC News |quote=The victims were connected to Instagram influencer Yekaterina Didenko.}}</ref> A similar accident occurred in 2018 when a woman died from {{CO2}} fumes emanating from the large amount of dry ice she was transporting in her car.<ref>{{Cite web |date=2 August 2018 |title=A Woman Died from Dry Ice Fumes. Here's How It Can Happen |url=https://www.livescience.com/63241-dry-ice-death.html |url-status=live |archive-url=https://web.archive.org/web/20210522082215/https://www.livescience.com/63241-dry-ice-death.html |archive-date=22 May 2021 |access-date=2021-05-22 |website=Live Science |language=en |vauthors=Rettner R}}</ref>
{{clear}}

==== Indoor air ====
Humans spend more and more time in a confined atmosphere (around 80-90% of the time in a building or vehicle). According to the French [[Agence nationale de sécurité sanitaire de l'alimentation, de l'environnement et du travail|Agency for Food, Environmental and Occupational Health & Safety]] (ANSES) and various actors in France, the {{CO2}} rate in the indoor air of buildings (linked to human or animal occupancy and the presence of [[combustion]] installations), weighted by air renewal, is "usually between about 350 and 2,500 ppm".<ref>{{Cite report |url=https://www.anses.fr/en/system/files/AIR2012sa0093Ra.pdf |title=Concentrations de CO2 dans l'air intérieur et effets sur la santé |date=July 2013 |publisher=ANSES |pages=294 |language=fr}}</ref>

In homes, schools, nurseries and offices, there are no systematic relationships between the levels of {{CO2}} and other pollutants, and indoor {{CO2}} is statistically not a good predictor of pollutants linked to outdoor road (or air, etc.) traffic.<ref>{{Cite journal |last1=Chatzidiakou |first1=Lia |last2=Mumovic |first2=Dejan |last3=Summerfield |first3=Alex |date=March 2015 |title=Is CO 2 a good proxy for indoor air quality in classrooms? Part 1: The interrelationships between thermal conditions, CO 2 levels, ventilation rates and selected indoor pollutants |url=http://journals.sagepub.com/doi/10.1177/0143624414566244 |journal=Building Services Engineering Research and Technology |language=en |volume=36 |issue=2 |pages=129–161 |doi=10.1177/0143624414566244 |s2cid=111182451 |issn=0143-6244}}</ref> {{CO2}} is the parameter that changes the fastest (with hygrometry and oxygen levels when humans or animals are gathered in a closed or poorly ventilated room). In poor countries, many open hearths are sources of {{CO2}} and CO emitted directly into the living environment.<ref>{{Cite journal |last1=Cetin |first1=Mehmet |last2=Sevik |first2=Hakan |date=2016 |title=INDOOR QUALITY ANALYSIS OF CO2 FOR KASTAMONU UNIVERSITY |url=http://www.universitypublications.net/proceedings/0903/pdf/H6V141.pdf |journal=Conference of the International Journal of Arts & Sciences |volume=9 |issue=3 |pages=71}}</ref>

==== Outdoor areas with elevated concentrations ====
Local concentrations of carbon dioxide can reach high values near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot spring near [[Rapolano Terme]] in [[Tuscany]], Italy, situated in a bowl-shaped depression about {{cvt|100|m}} in diameter, concentrations of {{CO2}} rise to above 75% overnight, sufficient to kill insects and small animals. After sunrise the gas is dispersed by convection.<ref>{{Cite book |title=Plant responses to elevated {{CO2}}: Evidence from natural springs |vauthors=van Gardingen PR, Grace J, Jeffree CE, Byari SH, Miglietta F, Raschi A, Bettarini I |publisher=Cambridge University Press |year=1997 |isbn=978-0-521-58203-2 |veditors=Raschi A, Miglietta F, Tognetti R, van Gardingen PR |location=Cambridge |pages=69–86 |chapter=Long-term effects of enhanced {{CO2}} concentrations on leaf gas exchange: research opportunities using {{CO2}} springs}}</ref> High concentrations of {{CO2}} produced by disturbance of deep lake water saturated with {{CO2}} are thought to have caused 37 fatalities at [[Lake Monoun]], [[Cameroon]] in 1984 and 1700 casualties at [[Lake Nyos]], Cameroon in 1986.<ref>{{Cite book |title=Plant responses to elevated {{CO2}}: Evidence from natural springs |vauthors=Martini M |publisher=Cambridge University Press |year=1997 |isbn=978-0-521-58203-2 |veditors=Raschi A, Miglietta F, Tognetti R, van Gardingen PR |location=Cambridge |pages=69–86 |chapter={{CO2}} emissions in volcanic areas: case histories and hazards}}</ref>