The choice of sampling tube material in the determination of nitrogen oxide concentrations in products of combustion

Abstract

It has been confirmed that when hot products of combustion containing traces of nitrogen oxides are sampled through metal tubes the concentration falls. The mechanism is in part due to the conversion of nitrogen dioxide to nitric oxide. Glass tubing may be used as a substitute at high sampling temperatures and PTFE is suitable at lower temperatures; nylon, EVA and PVC tubing should not be used since significant losses may occur in these materials even at room temperature.