Air pollution has become such an obsession for foreigners living in Beijing that international schools compete on the quality of their indoor air.

空气污染已经成为旅居北京的外国人如此在意的问题，以至于国际学校在室内空气质量上展开竞争。

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This can be costly if schools need air conditioning on hot days and school employees need to be paid for the extra time.

如果在暑天里学校需要空调并且学校需要支付雇员的加班费，这可能耗资巨大。

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This can be costly if schools need air conditioning on hot days and school employees need to be paid for the extra time.

这可能代价高昂，如果学校需要空调热天及学校员工，必须支付额外的时间。

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This can be costly if schools need air conditioning on hot days and school employees need to be paid for the extra time.

这可能代价高昂，如果学校需要空调热天及学校员工，必须支付额外的时间。

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