Microbiological controls of the environment in clean rooms are now included in most recommendations and regulatory documents. For example, in the guide “Bonnes Pratiques de Fabrication (BPF)”(1) it is recommended that limits and values of microorganisms in the air and on the surfaces are applied in the different clean room classes (A-D). This guide is the French translation of the guide for European Good Manufacturing Practice (2). In the hospital environment, the French standard NF390351 imposes microbiological values of the air and surfaces based on defined risk environments.