Outgassing is a process in which a solid releases gas. It is also known as offgassing, especially when people are talking about outgassing which occurs in enclosed environments such as offices and homes. This phenomenon occurs in nature as well as with manufactured products, and it can be involved in a number of different processes.
Solids can release gas for a number of different reasons. Some undergo phase changes which cause transitions from solid to gas, with the gas being released as a result. Others may have trapped gases inside as a result of the way in which they were formed, in which case the gas will slowly vent over time. Venting can increase if there are flaws in the material which create outlets for the gas.
Many people are familiar with outgassing because it is the phenomenon behind that distinctive new smell associated with many consumer goods. These products offgas for days, weeks, months, and sometimes years, with the smell gradually dissipating as the outgassing rate declines over time. It can become an issue because sometimes these gases are hazardous to human health, and prolonged exposure can make people sick.
Organizations which perform work in the vacuum of space also need to be worried about outgassing. The gas can potentially condense on equipment components, impeding function. For example, a camera lens might become obscured with gas which has outgassed from the housing of the camera. These organizations conduct research to find out which kinds of components outgas least in space, and they use tight quality control to make sure that the components they use are manufactured to tough standards which reduce errors.
In nature, things like rocks also outgas. In fact, outgassing may be at least partially responsible for the formation of some atmospheres, as rocks released trapped gas early in the formation stages of a planet or moon, thereby creating an atmosphere of sorts. In areas where geologic activity is high, outgassing is common, as gases may be trapped in the rocks from past geologic events. This is especially true around volcanoes, and sometimes generates distinctive smells which people can use to identify volcanic activity.
People can identify outgassing with the assistance of sniffers which are designed to measure levels of various gases in the air. These sniffers can be used in quality control and safety checks of various environments to determine whether or not release of gas is a health risk.