Editing Exhalation (section)

{{short description|Flow of the respiratory current out of an organism}}
{{For|the Ted Chiang short story|Exhalation (short story)}}
{{Redirect|Exhale}}
{{Redirect-distinguish|Expiratory|Expiration (disambiguation)}}
[[File:Expiration diagram.svg|thumb|Diagram showing expiration]]
'''Exhalation''' (or '''expiration''') is the flow of the [[breathing|breath]] out of an organism. In animals, it is the movement of [[air]] from the [[lung]]s out of the [[airway]]s, to the external environment during [[breathing]].
This happens due to elastic properties of the lungs, as well as the [[internal intercostal muscles]] which lower the rib cage and decrease thoracic volume.  As the [[thoracic diaphragm]] relaxes during exhalation it causes the tissue it has depressed to rise superiorly and put pressure on the lungs to expel the air.  During [[Hyperpnea|forced exhalation]], as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles generate abdominal and thoracic pressure, which forces air out of the lungs.

Exhaled air is 4% [[carbon dioxide]],<ref>{{Cite journal |last1=Carroll |first1=Gregory T. |last2=Kirschman |first2=David L. |last3=Mammana |first3=Angela |date=2022 |title=Increased CO2 levels in the operating room correlate with the number of healthcare workers present: an imperative for intentional crowd control |journal=Patient Safety in Surgery |language=en |volume=16 |issue=1 |page=35 |doi=10.1186/s13037-022-00343-8 |issn=1754-9493 |pmc=9672642 |pmid=36397098 |doi-access=free }}</ref> a waste product of [[cellular respiration]] during the production of energy, which is stored as [[Adenosine triphosphate|ATP]].  Exhalation has a complementary relationship to [[inhalation]] which together make up the [[respiratory system|respiratory]] cycle of a breath.

When a person loses weight, the majority of the weight is exhaled as [[carbon dioxide]] and [[water vapor]].