A chemical trace detection system includes: a drift tube; a detector disposed within the drift tube; a voltage source to produce an electrical field in the drift tube; an ionizer to establish an ionization region adjacent to the electrical field; and a desorber including a sample holder to hold a sample in or adjacent to the ionization region and a sample heater to desorb particles of the sample held in the sample holder such that the desorbed particles are introduced directly into the ionization region from the sample holder to form ionized particles that are forced toward the detector by the electrical field. A regenerable dryer assembly for supplying dry drift gas to an ion mobility spectrometer is also provided that includes a regenerable desiccant material.