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.
In a closed environment
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.[2] 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
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.[3][4]
From rock
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
References
- ↑ Strong, John (1938). Procedures in Experimental Physics. Bradley, IL: Lindsay Publications., Chapter 3
- ↑ "Health Concerns". United States Environmental Protection Agency. Retrieved 10 June 2013.
- ↑ Thin-Patch Repair of Concrete in Wastewater Environments Using Commercially Available Cementitious Resurfacers, Concrete Repair Bulletin, January 2008, retrieved 2014-10-21
- ↑ Preventing Air-Induced Coating Failures on Concrete, JPCL, January 2007, retrieved 2014-10-21