Several EU directives and national laws in European countries set requirements for continuous monitoring of flue gas emissions at power plants. Further requirements are set on the quality assurance of the installed measurement systems at the plants. The relevant standard in this regard is EN 14181, the quality assurance of automated measuring systems. The standard dictates how to determine that the measurement systems installed for continuous emissions monitoring at a plant operate according to the directives and regulations set. Two major parts of this on-going quality assurance cycle are the QAL2 and AST procedures. A test laboratory performs tests on the systems on-site and determines whether the systems fulfill the set requirements or not.