This guideline deals with the permanent installation-specific monitoring of individual parameters of controlled environments. The monitoring may be continuous (pressure, temperature, humidity) or sequential (microbiology). The guideline applies to the classical monitoring, i.e. permanent checking of parameters, but not for recurrent measurements for qualification purposes. The guideline does not specify microbiological techniques. It specifies methods the measurements on cleanroom installations and the required instrumentation so as to define a standard. The specifications regarding monitoring measurements aim at aiding the user in selecting methods allowing to determine installation- and process-related deviations from requirements during operation. The guideline does not apply to data loggers which store data to be read out at intervals. Data loggers, on the other hand, which immediately hand over data to a master system, i.e. loggers which are used merely as sensors, aare not excluded.