Patient gas delivery apparatus includes a gas flow generator, a gas delivery conduit and a patient mask (10). Connected in series between the conduit and the mask is an assembly (20) formed in at least two interengaging parts (26,28), which may form a housing for an anti-asphyxia valve or flow sensor. The assembly further includes a mating portion (22) for connection to the mask, the arrangement being such that connection of the assembly (20) to the mask (10) prevents disengagement of the interengaging connection (42,44) between the two parts of the assembly.
