A series of hollow tubes having, in sequence, tungstic acid, potassium-iron oxide, copper (I) iodide, and cobalt (III) oxide were employed by Braman et al. (1986) for determination of HNO3, HNO2, NO2 and NO from ambient air. Thermal desorption and detection of the NO released by a chemiluminescence detector provided an analysis of air for these compounds at subparts-per-billion concentrations. All components on the hollow tubes are thermally desorbed and detected as NO. The detection limit of this system is near 0.03 nmol of nitrogen compound.