Offgassing or outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material.[1] Offgassing can include phase transitions of a substance into a gas (sublimation and evaporation), as well as desorption, seepage from cracks or internal volumes and gaseous products of slow chemical reactions. Boiling is generally thought of as a separate phenomenon from offgassing because it consists of a phase transition of a liquid into a vapor made of the same substance.

Material reuse[edit | edit source]

Potential offgassing should be taken into consideration when repurposing or upcycling materials. Gases released from wood pallets, tires used in earthship construction,[2] or other materials may cause health issues.

In a closed environment[edit | edit source]

Offgassing can be significant if it collects in a closed environment where air is stagnant or recirculated. For example, "new car smell" consists of offgassed chemicals released by heat in a closed automobile. Even a nearly odourless material such as wood may build up a strong smell if kept in a closed box for months. There is some concern that plasticizers and solvents released from many industrial products, especially plastics, may be harmful to human health.[3] Some types of RTV sealants offgas the poison cyanide for weeks after application.[verification needed] Offgassing toxic gases are of particular concern in the design of submarines and space stations, which must have self-contained recirculated atmospheres.

In construction[edit | edit source]

The offgassing of small pockets of air near the surface of setting concrete can lead to permanent holes in the structure (called "bugholes") that may compromise its structural integrity.[4][5]

From rock[edit | edit source]

At the Earth's tectonic divergent boundaries where new crust is being created, helium and carbon dioxide are some of the volatiles being offgassed from mantle magma.

See also[edit | edit source]

References[edit | edit source]

  1. Strong, John (1938). Procedures in Experimental Physics. Bradley, IL: Lindsay Publications., Chapter 3
  3. "Health Concerns". United States Environmental Protection Agency. Retrieved 10 June 2013.
  4. Thin-Patch Repair of Concrete in Wastewater Environments Using Commercially Available Cementitious Resurfacers, Concrete Repair Bulletin, January 2008, retrieved 2014-10-21
  5. Preventing Air-Induced Coating Failures on Concrete, JPCL, January 2007, retrieved 2014-10-21

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