Air | Composition, Oxygen, Nitrogen

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'Air' from tourist destination on sale for $11 in Italy</a> <span class="font-14 text-gray-600"> <span>•</span> Nov. 5, 2024, 4:24 AM ET (NBC) </span> </div> </div> <div class="rest-of-recent-news-items"> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref41617"></span>air</strong>, mixture of gases <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="comprising" href="https://www.merriam-webster.com/dictionary/comprising" data-type="MW">comprising</a> the <a href="https://www.britannica.com/place/Earth" class="md-crosslink autoxref " data-show-preview="true">Earth’s</a> <a href="https://www.britannica.com/science/atmosphere" class="md-crosslink autoxref " data-show-preview="true">atmosphere</a>. The mixture contains a group of gases of nearly constant concentrations and a group with concentrations that are variable in both <a href="https://www.britannica.com/science/space-physics-and-metaphysics" class="md-crosslink autoxref " data-show-preview="true">space</a> and time. The atmospheric gases of steady concentration (and their proportions in percentage by volume) are as follows:</p><span class="marker MOD1 mod-inline"></span><div class="md-drag md-table-wrapper"><table> <tbody> <tr> <td><a href="https://www.britannica.com/science/nitrogen" class="md-crosslink autoxref " data-show-preview="true">nitrogen</a> (N<sub>2</sub>)</td> <td>78.084</td> </tr> <tr> <td><a href="https://www.britannica.com/science/oxygen" class="md-crosslink autoxref " data-show-preview="true">oxygen</a> (O<sub>2</sub>)</td> <td>20.946</td> </tr> <tr> <td><a href="https://www.britannica.com/science/argon-chemical-element" class="md-crosslink autoxref " data-show-preview="true">argon</a> (Ar)</td> <td>0.934</td> </tr> <tr> <td><a href="https://www.britannica.com/science/neon-chemical-element" class="md-crosslink autoxref " data-show-preview="true">neon</a> (Ne)</td> <td>0.0018</td> </tr> <tr> <td><a href="https://www.britannica.com/science/helium-chemical-element" class="md-crosslink autoxref " data-show-preview="true">helium</a> (He)</td> <td>0.000524</td> </tr> <tr> <td><a href="https://www.britannica.com/science/methane" class="md-crosslink autoxref " data-show-preview="true">methane</a> (CH<sub>4</sub>)</td> <td>0.0002</td> </tr> <tr> <td>krypton (Kr)</td> <td>0.000114</td> </tr> <tr> <td><a href="https://www.britannica.com/science/hydrogen" class="md-crosslink autoxref " data-show-preview="true">hydrogen</a> (H<sub>2</sub>)</td> <td>0.00005</td> </tr> <tr> <td><a href="https://www.britannica.com/science/nitrous-oxide" class="md-crosslink autoxref " data-show-preview="true">nitrous oxide</a> (N<sub>2</sub>O)</td> <td>0.00005</td> </tr> <tr> <td>xenon (Xe)</td> <td>0.0000087</td> </tr> </tbody> </table></div><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">The uniformity of <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="composition" href="https://www.merriam-webster.com/dictionary/composition" data-type="MW">composition</a> is maintained by mixing associated with atmospheric motions; but, above a height of about 90 km (55 miles), diffusional processes become more important than mixing, and the lighter gases (hydrogen and helium, in particular) are more abundant above that level.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">Of the gases present in variable concentrations, <span id="ref41618"></span><a href="https://www.britannica.com/science/water-vapor" class="md-crosslink ">water vapour</a>, <a href="https://www.britannica.com/science/ozone" class="md-crosslink autoxref " data-show-preview="true">ozone</a>, carbon dioxide, <a href="https://www.britannica.com/science/sulfur-dioxide" class="md-crosslink autoxref " data-show-preview="true">sulfur dioxide</a>, and <a href="https://www.britannica.com/science/nitrogen-dioxide" class="md-crosslink autoxref " data-show-preview="true">nitrogen dioxide</a> are of principal importance. The typical concentration ranges of these gases (in percentage by volume) are as follows:</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/winter-weather-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/84/193084-131-72E82D87/Iceland-glacier-lagoon.jpg" alt="Iceland, Glacier lagoon (Jokulsarlon)" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">Winter Weather Words Quiz</div> </div> </a><div class="one-good-fact-module"> </div><span class="marker MOD3 mod-inline"></span><div class="md-drag md-table-wrapper"><table> <tbody> <tr> <td>water vapour (H<sub>2</sub>O)</td> <td>0 to 7</td> </tr> <tr> <td>carbon dioxide (CO<sub>2</sub>)</td> <td>0.01 to 0.1 (average about 0.032)</td> </tr> <tr> <td>ozone (O<sub>3</sub>)</td> <td>0 to 0.01</td> </tr> <tr> <td>sulfur dioxide (SO<sub>2</sub>)</td> <td>0 to 0.0001</td> </tr> <tr> <td>nitrogen dioxide (NO<sub>2</sub>)</td> <td>0 to 0.000002</td> </tr> </tbody> </table></div><span class="marker PREMOD4 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="301494" data-asm-type="video"><div class="md-assembly-wrapper card-media " data-type="video" video-id="253596"><a data-id="253596" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/How-much-air-do-people-breathe-in-a-lifetime/-301494"><img src="https://cdn.britannica.com/96/253596-138-3435681B/How-much-air-do-people-breathe-in-a-lifetime.jpg?w=800&h=450&c=crop" alt="How much air do you breathe in a lifetime?" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/t83dZRQL.m3u8" } ], "image": "https://cdn.britannica.com/96/253596-138-3435681B/How-much-air-do-people-breathe-in-a-lifetime.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/EcWmx4cb.vtt", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/Z3ay1o0I.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="253596">How much air do you breathe in a lifetime?</span><span>Every minute, multiple liters of air are cycled through your lungs.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/science/air/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">Although present in relatively small amounts, these variable <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituents" href="https://www.merriam-webster.com/dictionary/constituents" data-type="MW">constituents</a> may be very important for maintaining life on Earth’s surface. Water vapour is the source for all forms of precipitation and is an important absorber and emitter of <a href="https://www.britannica.com/science/infrared-radiation" class="md-crosslink autoxref " data-show-preview="true">infrared radiation</a>. <span id="ref41619"></span><a href="https://www.britannica.com/science/carbon-dioxide" class="md-crosslink " data-show-preview="true">Carbon dioxide</a>, besides being involved in the process of <a href="https://www.britannica.com/science/photosynthesis" class="md-crosslink autoxref " data-show-preview="true">photosynthesis</a>, is also an important absorber and emitter of infrared radiation. Ozone, which is present mainly in the atmospheric region 10 to 50 km (6 to 30 miles) above the Earth’s surface, is an effective absorber of <a href="https://www.britannica.com/science/ultraviolet-radiation" class="md-crosslink autoxref " data-show-preview="true">ultraviolet radiation</a> from the <a href="https://www.britannica.com/place/Sun" class="md-crosslink autoxref " data-show-preview="true">Sun</a> and effectively shields the Earth from all <a href="https://www.britannica.com/science/radiation" class="md-crosslink autoxref " data-show-preview="true">radiation</a> of wavelengths less than 3,000 angstroms.</p><span class="marker MOD4 mod-inline"></span></section> <span class="md-signature"><a href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419">The Editors of Encyclopaedia Britannica</a></span> <span class="md-signature">This article was most recently revised and updated by <a href="/editor/Meg-Matthias/12593612">Meg Matthias</a>.</span><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":1,"pageId":10582,"pageLength":231,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"D","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"SMALL","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Air | Composition, Oxygen, Nitrogen | Britannica