Testing the testers

Abstract

A lack consistency of results between different test houses and methods could undermine the whole process of emission compliance with European legislation. Some of the principal factors which may affect the reproducibility of the results are: accuracy of the instrumentation, accuracy of the calibration gases, method of sampling, composition of the fuel, test rig air supply and fuel configuration, operation of the boiler, changes in temperature and humidity of the combustion air. This paper presents the research undertaken to investigate the effects of these factors on the measurement of NOx and CO, and to assist in the establishment of realistic confidence levels in published emission test results.