My room is 3×5 meters, it doesn't have a ventilation pipe connected to it, so the air becomes close very fast, and to freshen up the room I have to open the window, and it makes my room very cold. Leaving just a crack open doesn't give a lot of fresh air, but makes it cold and still hard to breathe.
Air conditioner doesn't really give me fresh air, instead it just heats or chills the air in the room.
What else is there to try to fix my situation?
My room is in an apartment, heated by central heating battery, only kitchens and bathrooms have ventilation connected to them in the building. Rooms are in their original state. The building is about 50 years old now, it's possible to change room from inside, probably impossible to make a hole to the outside.