An apparatus (10) for supplying breathable gas is disclosed. The apparatus (10) includes a main housing (12), a sub-housing (14), having a gas flow path (28) between a gas inlet (16) and a gas outlet (18), a motive power source (22) within the main housing (12) and an impeller (30) within the sub-housing (14) in fluid communication between the gas inlet (16) and the gas outlet (18). The impeller (30) is adapted to releasably engage the motive power source (22) external the gas flow path (28) and the sub-housing (14) is releasably connectable to said main housing. Also disclosed is a method of cleaning, sterilising or desinfecting the gas flow path (28) of the breathable gas supply apparatus (10). The method of cleaning comprising the steps of removing the sub-housing (14) from the main housing (12) cleaning, sterilising, desinfecting or replacing the sub-housing (14) and connecting the sub-housing (14) to the main housing (12).