Abstract: A chemical cell (40) containing silver nitrate is connected at the inlet (10) of an ion mobility spectrometer (1) so that sample gas for detection flows to the IMS via the chemical cell. When the sample gas contains arsine or phosphine, to which the IMS is not normally sensitive, this is converted by the silver nitrate in the cell (40) to nitric acid, to which the IMS is sensitive. In order to distinguish between nitric acid produced in response to arsine or phosphine and nitric acid present in the sample gas before supply to the cell (40), the inlet (10) is switched to receive sample gas directly.

Abstract: This invention relates to a novel air curtain device suitable for use in detecting certain characteristic vapors emitted from objects, particularly individuals, positioned therein. An air curtain having a uniform velocity profile is set up between first and second cabinets. Vapor detector probes are positioned in one cabinet downstream of the air curtain. Detectable vapors carried by an object, such as a person within the air curtain, are stripped off and transported to the vapor detectors. By positioning the vapor detectors remote from the object, a significantly higher number of objects can be screened using known vapor detection techniques within a given period of time.