Pressure gradients between internal and external enviroments generate in each type of building (both civil and industrial) an air flux directed to the lower pressure zone. This air flow is minimum if barred from walls or from efficient window and door frames while it increases with the lack of sealing of the under observation enviroment.
When the flow becomes siginficant we call it effect of VENTILATION. The natural ventilation is hardly and rarely effective and it is continually variable, making it unstrustable. Very often it is necessary to adopt ventilation fittings provided with mechanical devices (from grids to fans)
The employed systems can be classified into three main types:
External air Emmission
Extraction of the surrounding air
Combined Emmission and extraction
INDUSTRIAL VENTILATION
