[AIVC, Air infiltration and ventilation glossary, 1992]:(see mechanical ventilation system; mechanical extract ventilation system; mechanical supply ventilation system; balanced supply/extract ventilation system)[EN 16798-1:2019, 3.27]:combination of appliances or building components designed to supply indoor spaces with outdoor air and/or to extract polluted indoor air.Note 1 to entry: A ventilation system can refer to mechanical, natural and hybrid ventilation systems.Note 2 to entry: The ventilation system can consist of mechanical components (e.g. combination of air handling unit, ducts and terminal units). A ventilation system can also refer to natural ventilation systems making use of temperature differences and wind with facade grills. A combination of mechanical and natural ventilation is possible (hybrid systems).[EN 16798-3:2017, 3.7]:combination of appliances designed to supply interior spaces with outdoor air and to extract polluted indoor air.Note 1 to entry: The system can consist of mechanical components (e.g. combination of air handling unit, ducts and terminal units). Ventilation system can also refer to natural ventilation systems making use of temperature differences and wind with facade grills in combination with mechanical exhaust (e.g. in corridors, toilets etc.). Both mechanical and natural ventilation can be combined with operable windows. A combination of mechanical and non-mechanical components is possible (hybrid systems).