Dust masks are graded according to the protection they offer.

防尘面具根据其提供的防护而分级。

《柯林斯英汉双解大词典》

They are much more effective than the standard surgical masks or dust masks that are sometimes used by builders.

它们比标准的外科口罩或有时建筑工人使用的防尘口罩要有效得多。

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Thee market for dust masks and air purifiers is booming in Beijing because the capital has been shrouded for several days in thick fog and haze.

近几日北京持续被浓重雾霾笼罩，市场上防尘口罩和空气净化器的销量剧增。

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Deegan cautioned that workers in the disaster site should continue using dust masks and respirators and keeping the debris wet to reduce particulates in the air.

CNN: CDC, EPA: Little risk to public from sites

Four weeks after the attacks, New Yorkers are wearing dust masks on the streets downtown and hiring industrial cleanup crews to remove asbestos from their offices and apartments.

CNN: Recovery: NY seeks billions in federal aid