EN 50241-1:1999

Specification for open path apparatus for the detection of combustible or toxic gases and vapours - Part 1: General requirements and test methods

This European Standard specifies general requirements for the construction and testing of apparatus for the detection and measuring of combustible or toxic gases or vapours in ambient air by measuring the spectral absorption by the gases or vapours over extended optical paths, ranging typically from one meter to a few kilometers. Such apparatus measures the integral concentration of the absorbing gas over the optical path in units such as LEL meter for combustible gases and ppm meter for toxic gases. NOTE 1: Actual values of concentration can only be deduced where it can be established that the concentration is uniform over the optical path, as for example in very short optical paths (<100 mm). In such cases, the apparatus is within the scope of EN 50054 - EN 50058 and prEN 45544-1 to prEN 45544-4. Apparatus falling within the scope of this European Standard is classified as follows by the following types. Type 1: an optical transmitter and receiver, located at either end of a path through the atmosphere to be monitored. Type 2: an optical transceiver (i.e. combined transmitter and receiver) and a suitable reflector, which may be a topographic feature or a retroreflector, located at either end of a path through the atmosphere to be monitored. This European Standard does not apply to any of the following: 1. Apparatus intended to provide range resolution of gas concentration (e.g. LIDAR), 2. Apparatus consisting of a passive optical receiver without a dedicated optical source, 3. Apparatus intended to measure the local volumetric concentration of gas (point sensors), 4. Apparatus intended for the detection of dusts or mists in air, 5. Apparatus for cross stack monitoring, 6. Apparatus intended for the detection of explosives and vapours, and 7. Apparatus intended for quantitative and simultaneous multicomponent analysis, e.g. FTIR. This European Standard covering general requirements and test methods is supplemented by the following European Standard concerning specific requirements of performance: EN 50241-2: Performance requirements for apparatus for the detection of combustible gases. This European Standard is applicable to apparatus which is intended for use in both hazardous and non hazardous areas. Apparatus for use in hazardous areas which may contain potentially combustible atmospheres is required to be designed for safe operation, see 4.1.2. This European Standard applies to transportable, and fixed apparatus intended for commercial and industrial applications. NOTE 2: This European Standard and EN 50241-2 as referenced above are intended to provide for the supply of apparatus giving a level of performance suitable for general purpose applications. However, for specific applications a prospective purchaser or an appropriate authority may additionally require apparatus to be submitted to particular tests or approval. Such tests or approval are to be regarded as additional to and separate from the provisions from the European Standards