Good ventilation is a prerequisite for a good climate and the right temperature and heat indoors. There must be a balance between supply air and extract air in a home. The supply air is usually taken in through vents by windows and the exhaust air is usually sucked out through vents in kitchens and bathrooms.
Regardless of the type of ventilation in the property, it is important to keep the vents clean and not to block or close the fresh air intakes. This disrupts the system and results in air entering elsewhere, such as through the letterbox and leaks between windows and frames. Air that enters in this way can be unpleasant. The air in the apartment feels trapped if the vents are closed.
When cleaning an exhaust air valve, it is important not to change the setting of how much the valve should be open. Never completely unscrew the so-called "plate" - put some kind of marking on both the fixed and moving parts and you will get the "plate" back in the same way as before cleaning.