outlet port 6 is made to the connection manifold 8 of the cpap machine 3 in the same slide on motion the connection manifold 8 also provides an auxiliary outlet connection port 9 suitable for receiving a flexible respiratory conduit not shown to deliver humidified air to a patient the cpap machine 3 includes a heater base not shown in a chamber receiving bay 47 to heat the water chamber 2 and a securing means for securing the water chamber 2 to the cpap machine 3 the securing means is provided by a securing latch 19 and a slot 17 around the periphery of the chamber receiving bay 47 the slot 17 co operates with a flange 18 around the base of the water chamber 2 to secure the chamber 2 when in use the securing latch 19 operates to prevent removal of the chamber 2 once it has been engaged the securing means and connection manifold 8 are arranged with a parallel axis of operation such that connection of the chamber inlet port 5 and outlet port 6 to the connection manifold 8 is achieved as well as securing of the chamber into the cpap machine in the same slide on motion the latch 19 having a locking position and a release position is biased toward the locking position.