When exposed in air, stainless steels passivate naturally (due to the presence of chromium).

当暴露在空气中时，不锈钢就自动钝化。

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The last known case was in Britain in 1978 when a university photographer who worked above a lab handling smallpox died after being accidentally exposed to it from the building's air duct system.

众所周知的世上最后一例天花发生在1978年的英国。 那是一个（无辜的）大学摄影师，当时他正在天花实验室的楼上房间里工作，死于接触到大楼的风道系统偶然带出来的天花病毒。 （译者注：这位摄影师也太冤了。）

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Filthy-looking blackheads feed the misconception that acne grows on grime. In reality, sebum turns the color of mud when exposed to air.

看上去脏乎乎的黑头粉刺让人们往往误解为粉刺就是在尘垢上长出来的。事实上，皮脂在暴露在空气中时会转变成泥土的颜色。

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Despite the setback, Hull did not take long to regroup and exposed Boro's occasional vulnerability in the air when Nick Barmby's cross was converted by loan striker Manucho.

BBC: Middlesbrough 3-1 Hull