Air inside a structure will become stale if the area is not properly ventilated.
Ventilation of a structure means to provide a way for the fresh oxygen rich air that is on the outside to have a way to get inside and replace the stale air.
Even storage buildings or containers that do not have people inside them need ventilation.
Proper ventilation removes the odors that accumulate inside a structure as well as replacing the stale oxygen depleted air on the interior with oxygen rich fresh air from the outside.
This can be achieved in natural means by having windows and openings that can allow the movement of air through the structure.
Turbines on the roof of homes and buildings are designed to help the sir that is in the attic spaces to move through the attic and out of the structure.
There will also be vents located in the attics that allow the fresh air to flow into the space when the stale air is forced out.
In most buildings where there are large numbers of people the ventilation is taken very seriously.
If not done properly the people in the structure would not have enough oxygen to breathe and would take in too much carbon dioxide.
The accurate placement of windows, vents, fans, and other items that work together to ventilate a building are part of the design when the structure is built.
There are even regulations for factories, office buildings, institutions, and industrial operations on the exact amount of fresh air that must be forced into the building per person that occupies the space.
These regulations are different according to the type of operations that are performed inside the building.
For instance; a structure that houses a company that makes toxic chemicals requires a different venting system that a structure that is filled with office workers.
If the building allows people to smoke cigarettes and burn other forms of tobacco inside them the amount of fresh replacement air that is needed per person increases dramatically.
Typically the heating and air conditioning units that control the temperature inside the building are adequately providing enough venting to keep the air inside the building replenished.
Each structure has a different layout design for the duct work that transports the exhaust air out of the space and allows the fresh air to enter the space.
Without these venting systems a building that has twenty or thirty people inside it would quickly fill with odors from all of the perfume and normal body odors.
Wet rooms like the bathrooms would be unbearable due to the trapped odors inside them and large kitchens in restaurants would put out such an overpowering odor that the food would not be appetizing to the customers.
Nature meant for us to have a large supply of oxygenated air to breath and when we close ourselves into buildings we need to make sure that supply of oxygen can be found.
Otherwise we will be like a fish out of water.