Good point! Let me clarify the basic concepts of cleanroom. A cleanroom is an enclosed working space in which work is done that is delicate , and needs protecting from contamination by impurities in the ambient air. The air quality, the temperature and the humidity are regulated in order to protect the contents of the room from the dust and bacteriologically contaminated particles that exist naturally contaminated particles that exist naturally in the atmosphere and in the ambient air around the cleanroom, and also those that might be generated within the cleanroom itself.
A formal definition of a cleanroom is given in the international cleanroom standard (ISO 14644) as"A room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimise the introduction, generation,and retention of particles inside the room and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary."