在汽油机的一个测试循环中，约占排放污染物总量70%～80%的非甲烷碳氢化合物是在汽油机冷起动阶段没有经催化转化而直接排入大气中，造成严重污染。

In a testing of petrolic engine, about 70% to 80% of nonmethane hydrocarbon is emitted into atmosphere without catalysis conversion in theoment of coldstart, so that serious pollution is produced.

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