Describes the physical requirements for the safe operation of the process analyser measuring system installed in an analyser house in order to ensure its protection against fire, explosion and health hazards. Addresses the location of the analyser house and connection within the process plant areas, the design, construction and layout, measures for reducing the danger of explosion for analyser houses while permitting maintenance of equipment with the power on and the case open and those measures for protecting personnel from materials in the atmosphere of analyzer house that are hazardous for health. Does not address parts of the analyser measuring system installed in other locations such as sample conditioning rooms or swithgear rooms.