The invention is directed to an air heater for a gas chromatograph. The air heater has a core disposed inside a housing and includes an electrically resistive heating element. An air passage in the core extends parallel to a central axis of the air heater. A conduit extends parallel to the central axis of the air heater and is disposed farther outward from the central axis of the air heater than the air passage of the core. The conduit is connected between an air flow inlet and the air passage in the core such that when the air flow inlet is connected to an air source, air from the air inlet flows through the conduit to the air passage in the core and thence through an air flow outlet of the air heater. The air flowing through the conduit is cooler than the air flowing through the air passage in the core.