An apparatus (10, 10', 3010') for delivering a flow of gas comprising: a housing having an elbow retainer (160, 2160) and comprising a chamber bay for receipt of a removable liquid chamber; a removable elbow (342, 1342, 2342, 3342) that defines a gasflow passage (364, 1364, 2364) for a flow of gas; and a removable retention cover (150, 4150a, 4150b, 5150a) removably engageable with the housing; wherein the removable elbow (342, 1342, 2342, 3342) is configured to removably engage with the elbow retainer (160, 2160) wherein the elbow retainer (160, 2160) is configured to receive at least a part of the removable elbow (342, 1342, 2342, 3342) to removably engage therewith, wherein when engaged with the housing, the removable retention cover (150, 4150a, 4150b, 5150a) is configured to prevent removal of the removable elbow (342, 1342, 2342, 3342) from the elbow retainer (160, 2160), wherein the removable elbow (342, 1342, 2342, 3342) comprises a PCB electrical connector (366, 1366, 2366, 3366) for coupling to a complementary connector in the housing when the removable elbow (342, 1342, 2342, 3342) is connected to the housing, and wherein a first end of the removable elbow (342, 1342, 2342, 3342) comprises a gases inlet port (340, 1340, 2340, 3340) for coupling with an outlet gas port on a liquid chamber, and a second end of the removable elbow (342, 1342, 2342, 3342) comprises a patient outlet port (344, 1344, 2344, 3344) for coupling to a patient breathing conduit, and wherein, following receipt of the liquid chamber by the chamber bay and engagement of the removable elbow (342, 1342, 2342, 3342) with the elbow retainer (160, 2160) and engagement of the removable retention cover (150, 4150a, 4150b, 5150a) with the housing, the removable elbow (342, 1342, 2342, 3342) is configured to remain engaged with the elbow retainer (160, 2160) when the liquid chamber is removed from the chamber bay. a housing having an elbow retainer (160, 2160) and comprising a chamber bay for receipt of a removable liquid chamber; a removable elbow (342, 1342, 2342, 3342) that defines a gasflow passage (364, 1364, 2364) for a flow of gas; and a removable retention cover (150, 4150a, 4150b, 5150a) removably engageable with the housing; wherein the removable elbow (342, 1342, 2342, 3342) is configured to removably engage with the elbow retainer (160, 2160) wherein the elbow retainer (160, 2160) is configured to receive at least a part of the removable elbow (342, 1342, 2342, 3342) to removably engage therewith, wherein when engaged with the housing, the removable retention cover (150, 4150a, 4150b, 5150a) is configured to prevent removal of the removable elbow (342, 1342, 2342, 3342) from the elbow retainer (160, 2160), wherein the removable elbow (342, 1342, 2342, 3342) comprises a PCB electrical connector (366, 1366, 2366, 3366) for coupling to a complementary connector in the housing when the removable elbow (342, 1342, 2342, 3342) is connected to the housing, and wherein a first end of the removable elbow (342, 1342, 2342, 3342) comprises a gases inlet port (340, 1340, 2340, 3340) for coupling with an outlet gas port on a liquid chamber, and a second end of the removable elbow (342, 1342, 2342, 3342) comprises a patient outlet port (344, 1344, 2344, 3344) for coupling to a patient breathing conduit, and wherein, following receipt of the liquid chamber by the chamber bay and engagement of the removable elbow (342, 1342, 2342, 3342) with the elbow retainer (160, 2160) and engagement of the removable retention cover (150, 4150a, 4150b, 5150a) with the housing, the removable elbow (342, 1342, 2342, 3342) is configured to remain engaged with the elbow retainer (160, 2160) when the liquid chamber is removed from the chamber bay.