Abstract: Apparatus for the continuous metering of the vapors contained in the atmosphere.It comprises a thermoelectric module subject to the Peltier effect, which is supplied with electric power and whose hot face is in contact with a heat-dissipating radiator and whose cold face is in contact with a thermally insulated condensation chamber in which circulates the atmosphere charged with the vapors to be condensed, said chamber having a conductive metal structure provided with perforated ribs, the flow of the atmosphere and the temperature being permanently controlled at values such that the condensed vapor remains in the liquid state, the liquid condensate obtained flowing by gravity into the lower part of the chamber which, for this purpose, has a liquid phase discharge port.