Editing Carbon dioxide (section)

==== 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" />
|}