Abstract: In a gas chromatography oven, the heated enclosure is designed to be of a low thermal mass to permit more rapid programmed temperature changes, and to provide good oven cooling for work on the columns between analyses. Easy access to the columns is desirable, and accordingly, the present invention provides a heating enclosure having a door and at least one chromatograph column supported on a wall of the enclosure with the wall being transverse to the door opening and with the wall being movable from a first position having the column in the enclosure to a second position having the column outside of the enclosure. In such a structure, access to the column can be made outside of the enclosure so that the enclosure itself can be made smaller and of lower thermal mass.