This European Standard applies to both new and existing ventilation and air conditioning systems and specifies the assessment criteria of cleanliness, cleaning procedures of these systems, and the validation of the effectiveness of cleaning applies also to products, which conform to EN 1505, EN 1506, EN 13053, EN 13180 and EN 13403, used in air conditioning and ventilation systems for human occupancy defined in the scope of CEN/TC 156. This European Standard does not apply to installations for industrial processes. Cleanliness of ventilation systems is considered important for human comfort and health, energy consumption, system service life and for cleanliness of operations or processes carried out in the ventilated area. Considerations for change of component as an alternative for cleaning (e. g. in case of flexible ducts and air filters) are also included. This European Standard specifies general requirements and procedures necessary in assessing and maintaining the cleanliness of ducted ventilation, including: cleanliness quality classification; how to assess the need for cleaning (visual, measurements); assessment frequency (general guidance); guidance of system inspections in accordance with EN 15239, and EN 15240 when relevant; selection of cleaning method - to be in line with handing over documentation according to EN 12599; how to assess the result of cleaning. This European Standard is a parallel standard to EN 12097, which specifies requirements for dimension, shape and location for access panels for cleaning and service in ductwork systems. This European Standard is made as an umbrella standard with informative annexes that can be revised, completed and further added in future revisions of this European Standard for specific system types, and products or applications in the system, such as: Air Handling Units (AHU); filter; humidifiers; heat recovery units; decentralised air treatment units such as fan-coil units, induction units; terminal devices; kitchen extract equipment. The main target groups of this European Standard are specifiers of the cleanliness quality classes and cleaning methods primarily system designers who also specify the system of access, building owners, services companies, maintenance companies, end users and consultancy and control companies.