[AIVC, Air infiltration and ventilation glossary, 1992]:the delivery of outdoor or conditioned air to various spaces in a building, usually by mechanical means[EN 12792:2003, 16]:transportation of a specified air flow to or from the treated space generally by means of ducts. Along the ducts devices for the purpose of treating the air (e.g. cleaning, heating, cooling, humidifying or dehumidifying, etc.) and known as air treatment devices may be inserted.