The European Directives on waste incineration (2000/76/CE) and on large combustion plants (2001/80/CE) require to refer to international and national standards for emission monitoring and they specify requirements for the performance characteristics and the total uncertainty attached to the results provided by the automated monitoring systems (AMS) used for continuous monitoring. CEN TC 264 worked out in 2004 the EN 14181 standard which defines the various stages of quality assurance to be implemented to guarantee the reliability of the continuous emission monitoring. It applies to incineration and combustion plants but its use could be extended to other industrial plants after the publication of the future integrated European Directive which will replace the 7 already existing European directives. The EN 14181 standard specifies three levels of quality assurance (indicated by initials QAL) and an annual test of monitoring: (annual monitoring test indicated by initials AST).