a castle in the air
n. 空中楼阁

a change of air
改变环境, 迁地疗养

actual air consumption for fuel combustion
燃料燃烧所需实际空气量

additional air governor
补给空气量调节器

additional air regulator
补给空气量调节器

At the time when technology means ever more harmful carbon in the air we breathe,we need these forests now more than ever.
当技术的发展意味着我们会吸入更多有害气体时，我们比任何时候更需要森林。

I find young people exciting. They have an air of freedom,and they have not a dreary commitment to mean ambitions or love comfort. They are not anxious social climbers,and they have no devotion to material things.
我们位年强人振奋。它们带有自由的气息，他们不会为狭隘的野心和贪婪享受而孜孜以求。他们不是焦虑的向上爬的人，他们不会对物质性的东西难舍难分。

Let's take cars for example. They not only pollute the air in cities,but make them crowded. Furthermore,they are responsible for a lot of traffic accidents. The noise made by cars disturbs the residents living on both sides of streets all day and night.
就拿汽车为例。汽车不仅污染城市空气，而且使城市拥挤不堪。此外，汽车造成许多交通事故。汽车所产生的噪音使居住在街道两旁的居民日夜不得安宁。

The reason why we have to grow trees is that they can supply fresh air for us.
我们必须种树的原因是它们能供应我们新鲜的空气。

There is no denying the fact that air pollution is an extremely serious problem:the city authorities should take strong measures to deal with it.
无可否认，空气污染是一个极其严重的问题：城市当局应该采取有力措施来解决它。