Editing Outgassing

{{Short description|Release of a gas that was inside of some material}}
'''Outgassing''' (sometimes called '''offgassing''', particularly when in reference to [[indoor air quality]]) is the release of a [[gas]] that was dissolved, trapped, [[freezing|frozen]], or [[absorption (chemistry)|absorbed]] in some material.<ref>{{cite book |first=John |last=Strong |date=1938 |title=[[Procedures in Experimental Physics]] |publisher=Lindsay Publications |location=Bradley, IL }}, Chapter 3</ref> Outgassing can include [[sublimation (chemistry)|sublimation]] and [[evaporation]] (which are [[phase transition]]s of a substance into a gas), as well as [[desorption]], [[seepage]] from cracks or internal volumes, and gaseous products of slow [[chemical reaction]]s. [[Boiling]] is generally thought of as a separate phenomenon from outgassing because it consists of a phase transition of a liquid into a [[vapor]] of the same substance.

==In a vacuum==
Outgassing is a challenge to creating and maintaining clean high-[[vacuum]] environments. [[NASA]] and [[ESA]] maintain lists of materials with low-outgassing properties suitable for use in [[spacecraft]], as outgassing products can condense onto optical elements, [[thermal radiator]]s, or [[solar cell]]s and obscure them. Materials not normally considered absorbent can release enough lightweight [[molecule]]s to interfere with industrial or scientific vacuum processes. [[Moisture]], [[sealant]]s, [[lubricant]]s, and [[adhesive]]s are the most common sources, but even [[metal]]s and [[glass]]es can release gases from cracks or impurities. The rate of outgassing increases at higher [[temperature]]s because the [[vapor pressure]] and rate of chemical reaction increases. For most solid materials, the method of manufacture and preparation can reduce the level of outgassing significantly. Cleaning of surfaces, or heating of individual components or the entire assembly (a process called "[[bake-out]]") can drive off [[Volatility (chemistry)|volatiles]].

NASA's [[Stardust (spacecraft)|''Stardust'']] [[space probe]] suffered reduced image quality due to an unknown contaminant that had condensed on the [[charge-coupled device|CCD]] sensor of the navigation camera.<ref>{{Cite web |date=January 11, 2001  |title=STARDUST Vision Nearly Restored |url=https://stardust.jpl.nasa.gov/news/vision.html |url-status=dead |archive-url=https://web.archive.org/web/20090403014351/https://stardust.jpl.nasa.gov/news/vision.html |archive-date=April 3, 2009 |website=stardust.jpl.nasa.gov}}</ref> A similar problem affected the [[Cassini–Huygens|''Cassini'']] space probe's Narrow Angle Camera, but was corrected by repeatedly heating the system to 4&nbsp;°C.<ref name="jpl-20020723">{{Cite press release |date=23 July 2002 |title=Cassini Camera Haze is Removed |url=https://solarsystem.nasa.gov/news/12241/cassini-camera-haze-is-removed/ |url-status=live |archive-url=https://web.archive.org/web/20240715083900/https://solarsystem.nasa.gov/news/12241/cassini-camera-haze-is-removed/ |archive-date=15 July 2024 |access-date=14 October 2006 |publisher=[[NASA]] & [[JPL]] }}</ref> A comprehensive characterisation of outgassing effects using [[Mass spectrometry|mass spectrometers]] could be obtained for ESA's [[Rosetta (spacecraft)|''Rosetta'']] spacecraft.<ref>B. Schläppi, et al. (2010), Influence of spacecraft outgassing on the exploration of tenuous atmospheres with in situ mass spectrometry, J. Geophys. Res., 115, A12313, {{doi|10.1029/2010JA015734}}.</ref>

Natural outgassing is commonplace in [[comet]]s.<ref>{{cite journal|arxiv=1208.5480|doi=10.1051/0004-6361/201220169|title=An upper limit for the water outgassing rate of the main-belt comet 176P/LINEAR observed with ''Herschel''/HIFI|year=2012|last1=De Val-Borro|first1=M.|last2=Rezac|first2=L.|last3=Hartogh|first3=P.|last4=Biver|first4=N.|last5=Bockelée-Morvan|first5=D.|author5-link=Dominique Bockelée-Morvan|last6=Crovisier|first6=J.|last7=Küppers|first7=M.|last8=Lis|first8=D. C.|last9=Szutowicz|first9=S.|last10=Blake|first10=G. A.|last11=Emprechtinger|first11=M.|last12=Jarchow|first12=C.|last13=Jehin|first13=E.|last14=Kidger|first14=M.|last15=Lara|first15=L.-M.|last16=Lellouch|first16=E.|last17=Moreno|first17=R.|last18=Rengel|first18=M.|s2cid=118376416|journal=Astronomy & Astrophysics|volume=546|pages=L4|bibcode=2012A&A...546L...4D}}</ref>

==From rock==
Outgassing is a possible source of many tenuous [[celestial body atmosphere|atmospheres]] of [[terrestrial planet]]s or moons.<ref>{{cite book|url=https://books.google.com/books?id=HwdAAQAAIAAJ&q=Outgassing+is+the+source+of+many+tenuous+atmospheres+of+terrestrial+planets+or+moons|title=Encyclopedia of Planetary Sciences|last1=Shirley|first1=J. H.|last2=Fairbridge|first2=Rhodes W.|date=2001-01-31|publisher=[[Springer Netherlands]]|isbn=9780792367949|language=en}}</ref> Many materials are volatile relative to the extreme vacuum of [[outer space]], and may evaporate or even boil at ambient temperature. Materials on the [[lunar surface]] have completely outgassed and been blown away by [[solar wind]]s long ago, but volatile materials may remain at depth. The [[atmosphere of the Moon|lunar atmosphere]] probably originates from outgassing of warm material below the surface.

Once released, gases almost always are less [[density|dense]] than the surrounding [[rock (geology)|rocks]] and [[sand]] and seep toward the surface. [[Explosive eruption|Explosive eruptions]] of volcanoes result from water or other volatiles outgassed from [[magma]] being trapped, for example by a [[lava dome]]. At the Earth's [[divergent boundary|tectonic divergent boundaries]] where new [[crust (geology)|crust]] is being created, [[helium]] and [[carbon dioxide]] are some of the volatiles being outgassed from [[mantle (geology)|mantle]] [[magma]]. [[Alpha decay]] of [[primordial radionuclide]]s (and their decay products) produces the vast majority of the helium that continues to gas out of rocks on terrestrial planets.

==In a closed environment==
Outgassing can be significant if it collects in a closed environment where air is stagnant or recirculated. For example, [[new car smell]] consists of outgassed chemicals released by heat in a closed automobile. Even a nearly odorless material such as wood may build up a strong smell if kept in a closed box for months. There is some concern that [[plasticizer]]s and [[solvent]]s released from many industrial products, especially plastics, may be harmful to human health.<ref name="Health Concerns">{{cite web|title=Health Concerns [archived on archive.today]|url=http://www.epa.gov/dfe/pubs/projects/spf/health_concerns_associated_with_chemicals_in_spray_polyurethane_foam_products.html|archive-url=https://archive.today/20141203093542/http://www.epa.gov/dfe/pubs/projects/spf/health_concerns_associated_with_chemicals_in_spray_polyurethane_foam_products.html|url-status=dead|archive-date=2014-12-03|publisher=[[United States Environmental Protection Agency]]|access-date=2020-04-17}}</ref> Long-term exposure to solvent vapors can cause [[chronic solvent-induced encephalopathy]] (CSE). Outgassing toxic gases are of great concern in the design of [[submarine]]s and [[space station]]s, which must have self-contained recirculated atmospheres.

==In construction==
The outgassing of small pockets of air near the surface of setting [[concrete]] can lead to permanent holes in the structure (called [[bughole]]s) that may compromise its structural integrity.<ref name=crb>{{citation |url=https://www.icri.org/PUBLICATIONS/2008/PDFs/janfeb08/CRBJanFeb08_ODea.pdf |archive-url=https://web.archive.org/web/20200417005955/https://cdn.ymaws.com/www.icri.org/resource/resmgr/crb/2008janfeb/CRBJanFeb08_ODea.pdf |title=Thin-Patch Repair of Concrete in Wastewater Environments Using Commercially Available Cementitious Resurfacers |publisher=Concrete Repair Bulletin |date=January 2008 |access-date=2014-10-21 |archive-date=2020-04-17 |url-status=dead }}</ref><ref name=preventing>{{citation |url=http://www.macoatings.com/site/wp-content/uploads/2011/06/Maintenance_Tips_Preventing_Air-Induced_Coating_Failures_on_Concrete.pdf |title=Preventing Air-Induced Coating Failures on Concrete |publisher=JPCL |date=January 2007 |access-date=2014-10-21 |url-status=dead |archive-url=https://web.archive.org/web/20141022083612/http://www.macoatings.com/site/wp-content/uploads/2011/06/Maintenance_Tips_Preventing_Air-Induced_Coating_Failures_on_Concrete.pdf |archive-date=2014-10-22 }}</ref>

==See also==
*[[Lake Nyos Disaster]]
*[[Materials for use in vacuum]]
*[[Volatile organic compound]]
*[[Comet]]

==References==
{{Reflist}}

==External links==
*[https://outgassing.nasa.gov/ Outgassing Data for Selecting Spacecraft Materials Online (NASA database)]
*[http://esmat.esa.int/Services/outgassing_data/outgassing_data.html ESA Outgassing Data for Spacecraft Materials according to ECSS-Q-70-02]

{{HVAC|state=collapsed}}
{{Magmatic processes}}

[[Category:Vacuum]]
[[Category:Gas technologies]]
[[Category:Indoor air pollution]]