The reason for this lies in the buildings. These large buildings usually have Windows
that cannot be opened. The same air stays in the buildings for a long time and becomes unhealthy.
It may be full of chemicals that come from the furniture, the rugs, or the photocopy machines. Or it may be full of cigarette smoke, This unhealthy air causes "sick building syndrome, it is necessary to treat the building. the answer is simple more fresh air.