The vents provide fresh air needed for combustion and ventilation. This feature is very important, especially in buildings with good insulation level , where access of fresh air from outside is limited.
For the combustion process , a large amount of fresh air is needed.
Ventilation of homes and shops.
In a chimney , for complete combustion of 1 kg of wood it requires roughly 8m3 air . This air supply occurs through the vents.
They also provide fresh dry indoor air environment. In extreme cases, when there is no adequate supply of fresh air , inhalation of noxious gases may occur, with dangerous health effects.