This European Standard covers apparatus designed for checking the performance of heating appliances by measuring flue gas parameters of gas fired heating appliances for domestic residential and commercial applications. The apparatus may consist of different functional modules which may be tested separately for complying with this standard, and will be combined in different ways according to the different applications. Part 1 of EN 50379 specifies the general requirements and is supplemented by the requirements in EN 50379 2 and/or EN 50379 3. This European Standard specifies the performance requirements of portable spot reading apparatus designed to detect specific combustion flue gas parameters, such as concentration of gaseous compounds, temperature and/or pressure, to be used to decide if maintenance for the appliance is required and for adjusting the appliance during maintenance. This European Standard excludes apparatus for –checking appliances using fuels other than gas, –continuous emission, safety monitoring and control, and –use in vessels with an international load line. NOTE 1When this apparatus is used in industrial premises, national regulations should be observed. NOTE 2Apparatus may contain functional modules which are not covered by this standard e.g. measurement of smoke spot number (see EN 267:2009+A1:2011, Annex A) and/or measurement of indoor ambient air (see EN 50543).