But then farms began to use new ventilation systems.

VOA: special.2009.09.08

You handle them very special in terms of being extra careful in a very high ventilation area, in hoods is how you handle them.

在使用它们的时候你需要格外小心,必须在通风条件非常好的地方，在通风柜中才行。

麻省理工公开课 - 化学原理课程节选