还是要看具体情况.
只表达一般概念时直接使用
I like milk
具体指“一些”时用some/any
I need some milk.Do you need any (milk)?
特定用the
The milk in that glass is not good.
回到 fresh air
一般概念：
Fresh air is necessary to everybody.新鲜空气对每个人来说是必需的
具体“一些”
如果你在上班时走到户外,有人说你怎么跑到外面来了,你可以说
I need some fresh air
特定用the：
The fresh air here in the early morning is really good.