A NEW TEST GAS GENERATOR FOR ATMOSPHERIC TRACE COMPOUNDS

A new device for generating atmospheric trace gases for calibration pu rposes is described, which allows to adjust test gas concentrations wi th fast response times and constant carrier gas flow. It consists of a permeation tubing surrounded by a solution of the substance of intere st. Inside of the tubing a movable piston is placed. The position of t his piston determines the available fraction of the permeation surface and hence the output of the test gas source. The device has been test ed for the trace gas production of SO2 and formaldehyde in the ppbv ra nge. It shows linear dependence of the produced concentrations on the position of the piston, fast response times and good reproducibilities .