Abstract: A gas chromatography system having a chromatography column, a detector for analyzing sample components with a detection chamber connected to the column outlet, and a switching assembly for selectively alternately filling the detector chamber with carrier gas for a base line measurement and with effluent for analysis. The switching assembly includes a gas chamber connected to the detector chamber, a source of carrier gas and hot wire filament for selectively heating gas in the gas chamber to cause the carrier to be expelled from the gas chamber to fill the detection chamber for a base line measurement and for cooling gas in the gas chamber to withdraw the carrier gas from the detection chamber so as to draw effluent from the column outlet to thereby fill the detection chamber for an analytical measurement.