We should consider replacing some of these with windows which can be opened All ventilation is provided by the building's central air conditioning system At present this provides a mixture of 20% fresh air and 80% recycled air.

我们应该考虑用可以打开的窗户代替其中的一些。所有的通风都是由大楼的中央空调系统提供的。目前这提供了20%的新鲜空气和80%的循环空气的混合物。