Chemical trace detection system

A chemical trace detector comprises ion mobility spectrometer (IMS) 300 and regenerable dryer assembly 1200. The dryer comprises regenerable desiccant 1222 in chamber 1220. In an operating state, the dryer is coupled via valve 1240 to the IMS to supply dry drift gas pumped by pump 1210. In a regenerating state, the drift gas supply to the IMS is stopped at valve 1240 and a regeneration protocol is initiated. The desiccant is heated to a regeneration temperature, releasing water into gas flowing through the chamber and out of the system. The desiccant is cooled to an operating temperature, terminating the regeneration protocol, and the supply of dry drift gas to the IMS is resumed. The dryer may comprise a cooler. A controller may control the valve and heater, perhaps in response to a humidity sensor. The chamber may product drift gas with relative humidity less than 5%.