emission

n. discharge, emanation; ejection of fluids from the body

Emission generally means sending something out. It very commonly refers to flue gas or exhaust gas resulting from the combustion of fuels in a fireplace, oven, furnace, boiler, steam generator, gas turbine, automotive internal combustion engines, rocket engines and other equipment.
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Emission /emis·sion/ 1. discharge. 2. an involuntary discharge of semen. nocturnal emission reflex emission of semen during sleep. [more]Emission - Community and Resources

Noun
1. the act of emitting; causing to flow forth
(synonym) emanation
(hypernym) egress, egression, emergence
(hyponym) radiation
(derivation) emit, give out, give off
2. a substance that is emitted or released
(synonym) discharge
(hypernym) material, stuff
(hyponym) exudate, exudation
3. the release of electrons from parent atoms
(hypernym) release
(hyponym) photoemission
4. any of several bodily processes by which substances go out of the body; "the discharge of pus"
(synonym) discharge, expelling
(hypernym) bodily process, body process, bodily function, activity
(hyponym) ejaculation
5. the occurrence of a flow of water (as from a pipe)
(hypernym) flow, flowing

n. emission, discharge, emanation; ejection of fluids from the body