Laboratory Evaluation of Gas Dilution Systems for Analyzer Calibration and Calibration Gas Analysis

Abstract

Gas dilution systems can be used for multipoint calibrations of pollutant gas analyzers and for the analysis and certification of compressed gas calibration standards. This laboratory evaluation obtained estimates of the accuracy and precision of four representative gas dilution systems. Diluted and undiluted gas mixtures containing carbon monoxide, nitric oxide or sulfur dioxide in nitrogen were sampled by pollutant gas analyzers. Accuracies were estimated from the difference between the slopes of regression lines from measurements of the diluted and undiluted gas mixtures. These accuracy estimates ranged from −3.3 to 10.0 percent. Precisions were estimated from the 95-percent uncertainty for regression-predicted concentrations. These precision estimates ranged from 0.3 to 14.9 percent of the predicted concentration for mid-range dilutions.