Mould spores are widely distributed in the outdoor environment and, therefore, occur in varying concentrations also indoors. 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 problems affecting the occupants are closely related. DIN ISO 16000-16 specifies requirements for long-term (0,5 h to several hours) sampling of moulds in indoor air by filtration. During filtration, a defined air quantity is sucked through a filter on which separation of the suspended particles occurs. Airborne moulds are collected on gelatine filters resulting in a high total sampling efficiency. Due to stability and sampling efficiency reasons there is a polycarbonate filter downstream of the gelatine filter. The sampling device is constructed for the detection of particles of the size of mould spores (larger 1 µm to about 30 µm). After sampling the mould spores are cultivated and counted. This procedure is described in DIN ISO 16000-17.