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(US), vapor
1. particles of moisture or other substance suspended in air and visible as clouds, smoke, etc.
2. a gaseous substance at a temperature below its critical temperature
3. a substance that is in a gaseous state at a temperature below its boiling point



the gaseous state of matter that arises when the gas phase of a substance is in equilibrium with the liquid or solid phase of the same material. As a rule, the term “vapor” is used when a phase equilibrium is achieved at temperatures and pressures that are characteristic of natural occurring conditions. For example, one speaks of the vapors of alcohol, benzene, iodine, and naphthalene. However, the term “vapor” is also used to refer to the gaseous state of water above the critical values of temperature and pressure, even though such values are not obtained under spontaneous, natural conditions. Conversely, CO2 is referred to as a gas below the critical temperature of 31.04°C, even though by strict usage gaseous CO2 is a vapor, since it is found in the gaseous state under spontaneous, natural conditions (seeCRITICAL STATE). The terms “gas” and “vapor” are interchangeable in the terminology of the thermodynamics of phase transformations.

The vapor of a chemically pure substance is saturated at the saturation temperature and pressure and unsaturated at temperatures above the saturation temperature when the value of pressure is fixed. Unsaturated vapor, which in industrial terminology is called superheated steam or, simply, gas, is less dense than saturated vapor. A vapor is supersaturated when the pressure is raised above the saturation pressure while the temperature is kept constant.



A gas at a temperature below the critical temperature, so that it can be liquefied by compression, without lowering the temperature.
References in periodicals archive ?
TEHRAN (FNA)- Research Institute of Petroleum Industry (RIPI) experts have successfully implemented the project for gasoline vapor recovery at gas stations.
The impact of water vapor in compressed air systems can cause downstream equipment failure.
Both suits seek court orders requiring the defendants to protect people and the environment from the tank vapors.
Condensation of Ethylene Glycol on Integral-Fin Tubes"Effect of Fin Geometry and Vapor Velocity Trans.
Each dog trained in vapor wake detection must go through a six-month training at Auburn University, and pass a certification to be available for purchase.
Vapor intrusion may soon become an important environmental concern for commercial property owners, buyers, developers and lenders.
EPA issued Compliance Plans to both Tribes, who installed new vapor recovery systems that prevent release of harmful vapors.
All CETCO Gas Vapor Mitigation Systems are installed by a nationwide network of approved installers that have been trained and certified by CETCO.
Vapor phase was the original and principal mass reflow method for a few years in the early 1980s.
When the water droplets suddenly enter a warmer environment, they will evaporate into vapor [and the fog will disappear]," says Tardif.
Environmental Protection Agency, more than 374,000 sites nationwide may need to demonstrate to regulatory agencies that vapor intrusion does not pose a significant risk to human health.
Influence of 2,3 dimercaptopropane-l-sulfonate and dimercaptosuccinic acid on the mobilization of mercury from tissues of rats retreated with mercuric chloride phenylmercury acetate or mercury vapors.