What are these a/c vents used for?

[kordelb]

There are vents around my house...many to be exact...id say around 10 total that arent being used (at least i think) with the central a/c. In each room there are two vents (one at the base of the floor on the wall, and one towards the ceiling on the same wall) they dont have anything coming out of them yet when hand is pressed against it...i feel a slight air breeze coming out. Its like this in every room of the house even main rooms and no its not used for heating. We have main vents that are actually ON the ceiling that the A/C blows through now but i was wondering why these extra vents are here and what purpose they serve. (I have 2 A/C units connected to the house one per half of house. If possible id like to use these vents in conjunction with my other vents. But first things first, what are they for???

 

[ShanaeHelt]

There probably there for more air to be given of but there probably not hooked up or working.

 

[Unregistered]

One is an intake, the other is the outtake. The one at the roof takes in the hot air for "conditioning" (ie. cooling) and the bottom one then blows it back out. It is never a very strong force though, as it is a complete-cycle air conditioner, not just one that forces the cold air in.