dust concentration

例句：

1. 1. The factory isheavily contaminated with dust and mustbe cleaned frequently to maintain a safe workingenvironment.
   工厂被大量灰尘污染，必须经常清理以保持一个安全的工作环境。
2. 2. The dustconcentration in the air was high, makingit difficult for people to breathe.
   空气中的粉尘浓度很高，使得人们难以呼吸。
3. 3. Theengineer carefully measured the dust concentration before startingthe construction project.
   工程师在开始施工项目之前仔细测量了粉尘浓度。