Emission may refer to:

Chemical products

* Emission of

air pollutant Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...

s, notably: **

Flue gas Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced a ...

, gas exiting to the atmosphere via a flue **

Exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...

, flue gas generated by fuel combustion ** Emission of greenhouse gases, which absorb and emit radiant energy within the thermal infrared range *

Emission standard Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over ...

s, limits on pollutants that can be released into the environment *

Emissions trading Emissions trading is a market-based approach to controlling pollution by providing economic incentives for reducing the emissions of pollutants. The concept is also known as cap and trade (CAT) or emissions trading scheme (ETS). Carbon emission t ...

, a market-based approach to pollution control

Electromagnetic radiation

Emission spectrum The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a atomic electron transition, transition from a high energy state to a lower energy st ...

, the frequencies of electromagnetic radiation generated by molecular electrons making transitions to lower energy states *

Thermal emission Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is ...

, electromagnetic radiation generated by the thermal motion of particles in matter *

List of light sources This is a list of sources of light, the visible part of the electromagnetic spectrum. Light sources produce photons from another energy source, such as heat, chemical reactions, or conversion of mass or a different frequency of electromagnetic ener ...

, including both natural and artificial processes that emit light *

Emission (radiocommunications) Emission is the radiation or radio signal produced or emitted by a radio transmitting station.ITU Radio Regulations Radio regulation refers to the regulation and licensing of radio in international law, by individual governments, and by municip ...

, a radio signal (usually modulated) emitted from a radio transmitter *

Emission coefficient The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of t ...

, a coefficient in the power output per unit time of an electromagnetic source *

Emission line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

, or "spectral line", a dark or bright line in an otherwise uniform and continuous spectrum *

Emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emissio ...

, a cloud of ionized gas emitting light of various colors *

Emission theory Emission theory, also called emitter theory or ballistic theory of light, was a competing theory for the special theory of relativity, explaining the results of the Michelson–Morley experiment of 1887. Emission theories obey the principle of rela ...

, a competing theory for the special theory of relativity, explaining the results of the Michelson-Morley experiment *

Emission theory (vision) Emission theory or extramission theory (variants: extromission) or extromissionism is the proposal that visual perception is accomplished by eye beams emitted by the eyes. This theory has been replaced by ''intromission theory'' (or '' intromissi ...

, the proposal that visual perception is accomplished by rays of light emitted by the eyes

Other uses

Thermionic emission Thermionic emission is the liberation of electrons from an electrode by virtue of its temperature (releasing of energy supplied by heat). This occurs because the thermal energy given to the charge carrier overcomes the work function of the mate ...

, the flow of charged particles called thermions from a charged metal or a charged metal oxide surface, archaically known as the Edison effect *

Ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...

, the ejection of semen from the penis; also, specifically: **

Nocturnal emission A nocturnal emission, informally known as a wet dream, sex dream, nightfall or sleep orgasm, is a spontaneous orgasm during sleep that includes ejaculation for a male, or vaginal wetness or an orgasm (or both) for a female. Nocturnal emissions ...

, ejaculation experienced during sleep *

Noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

, emission *

Exhalation Exhalation (or expiration) is the flow of the breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of the lungs, ...

of air, especially in the context of musical instruments

Chemical products

Electromagnetic radiation

Other uses

See also