In the past, the material of choice has been carbon black, a sooty substance made by the incomplete combustion of petroleum products.

过去，备选材料为碳黑，这是一种石油产品不完全燃烧后形成的黑色物质。

Meanwhile, the incomplete combustion of gas in motor vehicles releases nitrous oxide.

同时，机动车燃气不完全燃烧会释放一氧化二氮。