Carbon dioxide
Carbon dioxide (CO2) was an odorless, colorless, nonflammable gas composed of one carbon atom and two oxygen atoms. It is expelled by animals and consumed by plants. 

In 2368, Data determined that the carbon dioxide in a soft drink he was having with  reacted with the polysaccharides therein to produce "an unusual combination of texture and effervescence." ()

Three subterranean pockets of carbon dioxide were located on Penthara IV. When the planet was struck by a type C asteroid and was threatened to freeze over because of a large cloud cover, the  phaser drilled large holes into the pockets in order to release the gas, thereby creating a greenhouse effect and preventing the world from freezing over. ()

The alien lifeform, later discovered to be Odo infected with volcanic gas, was determined to require a higher concentration of carbon dioxide than Deep Space 9's atmosphere provided. ()

The planet surveyed in the Gamma Quadrant by Jake and Nog had an atmosphere composed of 77% nitrogen, 21% oxygen and 2% carbon dioxide. ()

A dosage of fifteen ccs of tri-ox, given every four hours to a Human, can be used to compensate for excess carbon dioxide in a planet's atmosphere. ()

See also 
 Carbon monoxide
 Carbonated water

External link 
 

de:Kohlendioxid
Biochemical compounds