Mould is a common name for filamentous fungi from different taxonomic groups (Zygomycetes, Ascomycetes, Deuteromycetes). Most spores are in the size range 2 µm to 10 µm, while some go up to 30 µm and a very few up to 100 µm. Spores of some mould genera are small and become airborne very easily (for example, Aspergillus, Penicillium) while others are bigger and/or embedded in a slime matrix (for example, Stachybotrys, Fusarium) and are less mobile. Mould spores are widely distributed in the outdoor environment and, therefore, occur in varying concentrations indoors as well. Growth of moulds in indoor environments, however, should be considered a hygienic problem because epidemiological studies have revealed that dampness and/or mould growth in homes and health impairment of occupants are closely related. Standardized methods for sampling, detection, and enumeration of moulds, including standards for sampling strategies, are important for comparative assessment of mould problems indoors. During sampling, a defined quantity of air is drawn into the impactor. Commercially available slit or sieve samplers can be optionally used. The entrained particles and the mould dispersed in ambient air impact by diversion of the air flow and due to inertia on the plates correspondingly installed in the sampling device. The plates are covered with solid culture media. This part of ISO 16000 describes a method for active short-term sampling (1 min to 10 min) whereas an active long-term sampling procedure is carried out for (0,5 h to several hours) as specified in ISO 16000-16. After sampling, the mould spores are cultivated and counted. Cultivation is described in DIN ISO 16000-17. The whole method has been validated during comprehensive comparative measurements in several institutes. The document is directed at representatives of supervisory authorities, testing laboratories, professional associations and planning offices as well as representatives of interior designers, furniture industry, building industry, paint industry, adhesives industry or other branches producing items for the interior. The International Standard has been prepared by ISO/TC 146/SC 6 "Indoor air" in Working Group 10 "Fungi", the secretariats of which are held by DIN and which are under German chairmanship. The responsible German committee is NA 134-03-07-04-01 AK "Bioaerosole und biologische Agenzien" ("Bioaerosols and biological agents").