Air-air conditioning systems include centralised ventilation systems and all-air systems with air-conditioning units. These systems are linked to air-conditioning terminal units defined in the zones.

Central ventilation systems are as follows:

• Heat recovery unit
• Dedicated outdoor air system (DOAS)

Air handling units are classified according to the number of supply ducts and the type of control:

• Air handling unit, constant air flow system
• Air handling unit, variable airflow system
• Air handling unit, constant flow all-air system with double duct
• Air handling unit, variable flow all-air system with double duct