This International Standard specifies the applicable requirements concerning the design and use of ventilation systems in nuclear installations such as hot cells, nuclear fuel fabrication and examination laboratories, plutonium-handling facilities, reprocessing plants, enrichment facilities, nuclear-waste treatment stations, storage facilities, etc. The purpose of ventilation and containment systems is to and ensure safety functions and protect workers, public and environment against the spread of radioactive contamination resulting from the operational processes of these installations. This International Standard does not apply to the containment envelope of nuclear power plants and some research reactors where high pressure can occur during accident scenarios. It does apply to auxiliary rooms of these facilities. The requirements for the design and use of ventilation systems that ensure safety functions in nuclear reactors will be developed in another International Standard.