emitter
noun [ C ] uk/ɪˈmɪt.ər/ us/ɪˈmɪt̬.ɚ/
发出者;发射者
something that emits (= sends out) light, a noise, or a substance, especially the gas carbon dioxide
SUVs remain, on average, higher emitters than passenger cars. 平均来说，运动型多用途车比轿车排放的废气要多。