A gas chromatograph oven including a housing, a capillary tube and a thermal control assembly. The housing defining a capillary tube receiving space and having at least one outlet port to permit the passage of a fluid from the capillary tube receiving space of the housing. The capillary tube is positioned in the capillary tube receiving space of the housing and has a gas inlet end connectable to a gas injector and a gas detector end connectable to a gas detector. The thermal control assembly is in fluid communication with the capillary tube receiving space of the housing and is connectable to a source of a temperature regulating fluid.