The in-flight sensitivity of gold-tube NOy converters to HCN

In-flight measurements of the HCN conversion efficiency of three gold-tube NOy converters were made during the recent TOTE/VOTE and SUCCESS aircraft projects. While sampling ambient air and with the upstream addition of 500 ppmv H2O, two converters had HCN conversion efficiencies averaging about 5%. The H2O addition was a routine part of the NOy measurement procedure for these projects. A third converter showed much higher HCN conversion, about 30%. Conversion efficiencies determined while sampling synthetic air were significantly higher than those measured while sampling ambient air. The dependence of conversion efficiency on ambient H2O and O-3 was minimal, at least with respect to the variability of the measured values over the course of the missions.