I previously had read some articles online that said air conditioners like this don't do ventilation. The air inside the room keeps entering the indoor unit and cold air is blown into the room again and it keeps going on.
But recently, I had an argument with my electrician. He said you must close every smallest gap in the room to block outside air/atmosphere. Now I can understand the purpose of it, like it will reduce my electricity bill and room will maintain coolness.
But he gave another reason. When I said I don't want to close everything in the room except the door (I tend to keep a small window open so there's still room for fresh air, because I feel when the room is completely closed, CO2 from breathing will increase in the room) so there's some scope for ventilation (indirectly). He said are you mad. Split ACs themselves do ventilation. The outdoor unit on your roof helps do ventilation, so the air in your room is always fresh and cool. It moves the so called CO2 and hot and bad air from the room to the outer atmosphere.
So when this argument continued, I doubted myself and what I had read previously. I Googled again and saw no conclusive evidence that says a split AC does ventilation.
So I'm looking for a more authentic reference/answer which describes whether or not the split AC does ventilation.
Here are two examples of type of AC I'm concerned about:
One and Two.
Best Answer
No. Obviously not.
First hit on Google, when asking "does a split airconditioner provide fresh air"
https://www.delcohvac.com/blog/do-air-conditioners-take-in-outside-air/
Split Airconditioner
Have a look at how a split AC is installed:
There is an exchange of "heat" through the refrigerant tubing (hot liquid goes out, comes back cold), but no air is exchanged. The inside unit it placed against a wall and it has no air access to the outside. In fact this is a practical and aesthetic selling feature: it does not require a window.
Filters in a split AC
The filter in the outside and inside units are not to filter fresh air entering the house, obviously, but to keep the air exchanger clean so that they work more efficiently. Dust, dirt and grim (dust & fat) that covers the metal exchanger forms an insulating layer like a coat blanket, and reduces the heat exchange necessary to provide cooling.
Window air conditioner with outside-air intake
A window air conditioner is different: because it has a access to the outside, it can pull-in or push-out a small amount of air while running, thus directly exchanging the air in the room it cools.
Heres's a diagram and it shows a "damper". It is a flap at a small opening that connects inside with outside. When the AC runs, the fans create a small pressure difference at the flap that then opens allowing entry of outside air:
Exchanging Air
If you wish to provide fresh air into the living space, you need a separate ventilation system for that. You can theoretically leave a door open, or run a fan to circulate air in & out of a gap in the window, but these will cost a lot in lost cooling (summer) or lost heating (winter).
An ERV or HRV is different from a simple crack in the door or a fan at the window because the air that is drawn in is cooled using the "coolness" of the air that is sent out. You need power to run the fans, but the cooling comes for free.
ERV
In a hot an humid climate you would use a ERV instead. An "Energy Recovery Ventilator" will exchange inside air for outside air, replacing the stale air with (hopefully) more fresh outside air, and it will help keep the humidity inside low even if the hot but fresh outside air is humid.
HRV
If humidity is not a concern you can use an HRV (Heat Recovery Ventilator), which is practically the same but without the moisture exchange.
Have a look:
Stale inside air goes out and better outside air is pulled in.
Heat Exchanger
That cubic-shaped block in the middle brings the two flows of close to each other, flowing over aluminium plates, to allow the temperature to equalize through the metal: the fresh outside air is cooled a bit by the air sent out, so that the air conditioner does not have to cool it as much as when your draw-in hot air from the outside.
Further reading in ERV vs HRV:
https://www.ecohome.net/guides/2276/choosing-between-an-hrv-and-an-erv/
Image credits:
https://www.pinterest.ca/pin/469781804853382012/
https://www.pvhvac.com/blog/erv-or-ventilating-dehumidifier-which-is-better-for-georgia-homes
https://www.engineeredair.com/index.php/our_products/category/energy-recovery-and-iaq-products
https://www.brighthubengineering.com/hvac/55429-how-to-install-window-air-conditioner/