大廈外牆冷氣機台是屬於公眾地方或是某單位業主擁有??

The answer is neither - it is known as an easement.

Easement is basically a right to use even there is no ownership involved.

In your case, the area is as an easement owned as a public area but the owner of the property connecting to that area has the exclusive right to use.

It is why:

1. Your owners' corporation can regulate how you use the space (like the size of the air conditioning);

2. You will be liable if the air conditioning has issues.

呢樣野就一定要睇公契,而一個所謂冷氣機平台,係分出使用權同埋擁有權,譬如大廈公家地方,住客一般都係只有使用權而非有一個絕對擁有權.

一般黎講,大業主係會保留外牆既擁有權,呢個係題外話,而就算大業主對外牆有業權,但唔亦代表小業主唔關事,好幾年前,太古城就嘈過,外牆就由太古擁有,但維修費就由小業主比.

除非走廊都有冷氣。。。。。。。

當然是單位業主擁有啦, 有冇可能俾公眾地方你放冷氣機?