A cleanroom or ultra-clean room is a space in which the concentration of airborne particles is kept very low. Biotechnology requires the construction of clean rooms and associated clean room areas, in which one strives to control the concentration of airborne particles, temperature, humidity and room pressure. The activities in this sector are diverse: safety laboratories, R & D laboratories, production unit, bio-exclusion areas, animal holding rooms, etc. The clean room is protected by an enclosure, i.e. a physical barrier with walls, ceilings, doors and floors between different areas (classified and/or unclassified areas), which must meet design criteria or provide very specific performances (mechanical strength, hygiene, geometry, ergonomics, fire behavior, soundproofing, etc.). Clean rooms used as animal holding rooms for production are defined by a classification of risk areas from class 1 (cannot cause human disease) to class 4 (can cause serious human disease with a risk of environmental contamination). Animal holding rooms in biotechnology operate in containments whose containment classes are mainly classes A1 to A4. R & D laboratories operate in containments whose containment classes are mainly classes 2, 3 and 4 (called L2, L3 and L4). Other applications of cleanrooms or cleanroom technology can be found for special manufacturing processes – especially in semiconductor production, where particles in ordinary ambient air would disrupt the structuring of integrated circuits in the range of fractions of a micrometer. Also in optics and laser technology, aerospace engineering, life sciences and medical research and treatment, research and aseptic production of food and pharmaceuticals, and nanotechnology.