This International Standard specifies performance tolerances and the technical data presentation of industrial fans of all types. It does not apply for fans designed solely for low-volume air circulation, such as those used for household or similar purposes (ceiling and table fans, extractor fans, etc.). For jet fans refer to ISO 13350. The upper limit of fan work per unit mass is normally 25 kJ kg−1, corresponding to an increase of fan pressure of approximately 30 kPa for a mean density in the fan of 1,2 kg m−3. For higher values, agreement is to be reached between the supplier and the user. This International Standard embraces the four installation categories defined in ISO 5801: A free inlet, free outlet; B free inlet, ducted outlet; C ducted inlet, free outlet; D ducted inlet, ducted outlet. The performance of a fan can vary considerably with the installation category it is operating within. Therefore, these categories form an important part of the definition of the fan’s technical data presentation. NOTE International acceptance of the four installation categories provides the opportunity to base a contract on the most appropriate fan category for the end user and the system designer. Correspondingly, the likelihood of the fan providing the agreed performance, without compromise or concession, is enhanced.