Offgassing or outgassing refers to the release of chemicals from various substances under normal conditions of temperature and pressure. Offgassing can take a variety of forms, and is an issue of concern for some people, since some of the chemicals released during the offgassing process are potentially harmful. A number of studies have been conducted on offgassing of various chemicals in an assortment of environments with the goal of determining the risk of offgassing to human health.
You can probably think of a few examples of outgassing. For example, when an area is painted, varnished, or stained, a strange scent often lingers for a few days. This is offgassing, and the strange scent is caused by volatile organic compounds, some of which are potentially hazardous. Many plastics also offgas. Inhaling these chemicals or absorbing them through the skin and mucus membranes can be very harmful.
Offgassing is a special issue of concern when it takes place in an enclosed environment. For example, new cars have a distinctive and famous smell which is actually caused by offgassing. Some people fear that the enclosed environment of the car concentrates the chemical compounds, since they cannot escape, and this could make riding in a car dangerous. The enclosed space concern also explains why people are told to open windows and doors after painting, to help the room dry and to keep the space ventilated.
When smelly chemicals outgas, people are made aware of the issue. Of greater concern is chemicals which do not have odors, as some of these chemicals are very dangerous, and they can cause immediate health effects as well as long term damage. It is possible to use specialized chemical sniffers to search for such chemicals in the air; sniffers can also determine the levels of these chemicals to see how dangerous they are. Offgassing can also be harmful to the environment.
In some cases, dangerous levels of offgassing have been linked to cheap building materials. For example, the inexpensive portable classrooms used by many school districts as a temporary measure to accommodate growing student bodies have been linked with health problems caused by the offgassing of chemicals like formaldehyde. Ironically, levels of offgassing tend to be very high in these structures because of the materials used as fire retardants. These materials are designed to make portable classrooms safer for students and teachers, and sometimes the manufacturer is unaware of the hidden dangers.