Unusual biogenic indoor contaminants, their outdoor effects and their continuous measurement

In the immediate surrounding of a flour processing factory there was reclamation about extensive biogenic contaminations on building surfaces. An investigation revealed that starch particles from wheat flour served as nutrient for the growth of dematiaceous fungi. Several years after apparent removal, the problem reoccurred. A fundamental examination of the facility was conducted and different potential emission sources of starch particles were detected. The special challenge of the subsequent investigation was the continuous measurements of starch emissions. Particle traps according to the Hirst principle, in combination with consecutive staining allowed the chronological documentation of starch particle release. Finally the outlets of the ventilation system of the production building were identified as the main source and countermeasures could be taken. The investigation presented here demonstrates a remarkable case of interaction between indoor particle contaminants and outdoor air microbiology.