It can be put on a tree around your house to test the air quality.

你可以把它放在你房子周围的树上来测试空气质量。

youdao

Between August 17 and 20, the Beijing organising committee conducted studies of air quality during test events.

8月17日至8月20日，北京组委会在测试赛期间对空气质量进行了研究。

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A test run of the transportation component of the pollution reduction plan conducted last summer resulted in undetectable air quality improvements.

去年的一项交通减少污染的计划的测试(去年7月的单双号试行)以对空气质量改善的无法察觉而结束。

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The air quality was monitored during last summer's test events in Beijing, with no health problems reported and findings indicating the health of the athletes was not impaired.

BBC: Rogge admits Beijing air concern