Science, Tech, Math › Science Emissions Definition in Chemistry Share Flipboard Email Print Emissions are products of combustion aside from heat. Galdric Pons / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 21, 2020 In chemistry, emissions are the products produced other than heat in a combustion reaction. Since combustion is a chemical reaction in which a fuel is oxidized, all fires and flames produce emissions. Examples Carbon dioxide is a common emission from combustion reactions. Other possibilities include sulfur and nitrogen oxides. Some flames produce soot.