I have a doubt. Does air conditioners cool and re-circulate the air present inside the room, or does it takes in the air outside the room, cools and sends it inside ?.
If it cools and recirculates the air present inside the room, then over a period of time will the CO2 content of the room increase ?
Most of them have two portions. The cold portion is like an automobile radiator and is inside the room. The other portion is the hot radiator and is outside the room. A fan circulates outside air through the outside radiator and expels it outside.
Most units have two options for the source of air for the inside, cold radiator. In normal mode air is taken from outside the room. In fast cool mode the air is from inside the room. As you stated, this last mode has health issues and should be done infrequently.
It all depends. The cold radiator collects water from the air that passes through it and the water drips down into a collecting basin. It all depends on what happens next to the water. Most of the time it is sent to the outside part of the unit and thus into the air outside the building.
I suspect that some units are designed to counteract this problem by putting the water back into the inside the room air.