A solvent dumping apparatus is described having an inlet enclosure coupled to the inlet of a detector and an outlet enclosure coupled to the outlet of a detector. Venting means are provided for both enclosures, one of which is controllable; means are provided for introducing sample gas into the inlet enclosure; and means are provided for introducing gas into the outlet enclosure. During a detection mode, at least one of the venting means is so adjusted as to cause sample gas to flow through the detector and out the venting means for the outlet enclosure, and during a diversionary mode, at least one of the venting means is so adjusted as to cause the gas introduced into the outlet enclosure to pass back through the detector and carry any sample gas out through the venting means for the inlet enclosure. In preferred forms of the invention, one of the venting means is a back pressure regulator.