A continuous-flow trace vapour source

Abstract

A continuous mode device for generating mixtures of air and the vapour of a high boiling-point substance is described. Such a device is useful for calibration purposes in vapour trace detection work. Two streams of air, one containing the vapour and a second one diluting it, are mixed in an adjustable ratio so that low-level concentrations of the vapour in an air stream can be obtained. Concentrations can be kept constant over a wide range extending to the sub-PPB region. The vapour source has been used to generate the vapours of various explosives and pesticides; the results for ethylene glycol dinitrate, dinitrotoluene and fenitrothion are presented in this paper.