Two weeks after repair of a shower drain, an unnoticed leak resulted in large-scale water penetration into the blood product fractionation room. Both 120-m2 of floor and 10-m2 of wall were heavily soaked. Such a situation usually required the immediate interruption of manufacturing, and start of maintenance work. However, as this service provides blood products for an university hospital, it was necessary to ensure the maintenance of good manufacturing practices and product safety by implementation of a bundle of preventive measures. For forced drying, the floor covering was completely removed, the drywalls were opened, and damp insulating material was removed. For 11 weeks, room air dryers were installed. Simultaneously, a moisture and microbiological monitoring and disinfection regime were implemented. In the leaked water, no faecal microbial pathogens or moulds were detected. Within three days the humidity was decreased from 72% to 31%. Because of the accelerated disinfection regime, the indoor air bacterial and fungal contamination was reduced below normal values; neither on working surfaces nor on manufacturing devices was critical microbial contamination detected at any time. Immediately implemented drying measures accompanying disinfection regimen and microbiological monitoring were able to restore safe indoor air quality and re-establish the aseptic quality.