The intention behind this technical specification is to provide guidance concerning the way in which the air-borne contamination of surgical sites and medical devices can be minimised in operating rooms and adja-cent rooms. The aim is to prevent post-operative infections caused by airborne microorganisms. The tech-nical specification gives functional requirements, guidance concerning the technical design of ventilation systems and describes methods for evaluating the capacity of ventilation systems to remove microorganisms from the air. The interaction between clothing systems and air flow is also described. Other important measures to ensure cleanliness in operating rooms are cleaning/preparation of the room before and after an operation, working methods and traffic flow for patients and staff. These areas are considered but are outside the actual framework of the technical specification. Fire risks are not addressed in the specification.