OIML Recommendation R 144

Instruments for the continuous measurement of CO and NO_x in stationary source emissions

Scope: This Recommendation applies to measuring instruments (hereafter referred to as "gas analytical systems") that serve to determine the volume fraction of carbon monoxide (CO), nitrogen monoxide (NO), nitrogen dioxide (NO₂), or sum of nitrogen oxides (NO_x) and establishes the conditions and requirements with which such systems shall comply in order to meet the requirements for measurement results of the pollutant content in stationary source emissions within OIML Member States.