The Eldex Labs 725-1010 Column Heater is a column heater that is designed to provide the precise, controlled thermal environment necessary for reproducible qualitative and quantitative analysis in HPLC. Up to four columns ranging from 10 to 30 cm long and from 1/4 to 1/2 inch OD are supported within a thermally insulated block by interchangeable aluminum inserts tailored to the column. Channels in the interior surface of the heater provide good thermal contact for inlet/outlet tubing to assure reproducible equilibration. Temperatures from approximately 30°C (5 degrees above ambient) to 150°C are maintained within 0.1 degree by a precise adjustable control unit. A fail-safe circuit shuts off the power to the unit if the temperature exceeds approximately 155°C. The flexible sealing of the heater assembly allows inlet and outlet tubing to be routed into the unit at any point in order to minimize tubing length and extra-column dead volume.