This Technical Specification describes the measurement of moulds in ambient air in order to identify, quantify and characterize bioaerosol pollution in ambient air resulting from emissions from different sources. The method described specifies the sampling of moulds as part of the suspended particulate matter (SPM, here particles with aerodynamic diameter up to ca. 30 µm) using a filter sampling system with gelatine/poly-carbonate filter combination followed by the culture-based analyses on DG18 agar. The sampling duration can be varied between 10 min to 24 h. The health effect of bioaerosols is not limited to any particle fraction, therefore, this document describes the sampling of moulds as part of the suspended particulate matter as a convention method. NOTE The sampling method described in this document in principle is likely to be appropriate for the sampling of actinomycetes and other spore-forming bacteria (resistant to desiccation). For these species a special analytical procedure using different culture media should be applied, but this is not within the scope of this document. The standard method set out in this Technical Specification is accepted by convention as reference method. The measured quantity, here the number of colony forming units per cubic meter (CFU/m3), is determined by the inlet design of the sampling head, the associated operational parameters and the analytical procedure. Standardized methods for sampling, detection and enumeration of moulds including standards for sampling strategies are important for comparative assessment of moulds in ambient air. Before doing any measurements a plan for the measurement strategy is necessary (see CEN/TS 16115-2 ).