Gas cooler and method for cooling gas

There is disclosed a gas cooler 20 for providing high-pressure sealing gas to a bearing chamber. The cooler comprises a turbine 22; a turbine inlet 24 arranged to receive gas to drive the turbine and a turbine outlet 26 arranged to deliver gas output from the turbine; a compressor 28 arranged to be driven by the turbine 22; a compressor inlet 30 arranged to receive gas to be compressed by the compressor and a compressor outlet 32 arranged to deliver gas output from the compressor 28; and a cooler outlet 36 in fluid communication with the turbine outlet 26 and the compressor outlet 32 so as to deliver high-pressure sealing gas comprising gas merged from the turbine outlet 26 and the compressor outlet 32.