There is provided a gas heat exchanger 101 comprising a coolant conduit 102 having a coolant inlet 103 and a coolant outlet 104, a gas cooling conduit 201, and a gas bypass conduit 203. At least a portion of the gas cooling conduit 201 is disposed between at least a portion of the coolant conduit 102 and a portion of the bypass conduit 203. During a first mode of operation, the gas cooling conduit 201 is configured to carry gas. During a second mode of operation, the bypass conduit 203 is configured to carry gas and the gas cooling conduit 201 is configured to reduce a heat exchange between the coolant conduit 102 and the bypass conduit 203.