A humidification chamber (50, 300, 400, 500) for humidifying gases, comprising: a water tub that is configured to receive a volume of water, the water tub comprising a base surface having a heater plate; a lid (56, 456) hingedly coupled to the water tub for enclosing the water tub to define the interior volume of the humidification chamber (50, 300, 400, 500) and which is movable between a closed position in which the water tub is closed by the lid (56, 456) and an open position in which the water tub is open; at least one operable clip (170, 190, 200, 210, 290, 560) provided on either the lid (56, 456) water tub which is configured to engage with a complementary catch (172, 192, 212, 312) provided on the other of the water tub or lid (56, 456), for securing the lid (56, 456) in the closed position; a gases inlet in the lid for receiving a flow of gases into the interior volume of the humidification chamber (50, 300, 400, 500), the gases inlet having an associated inlet conduit that extends between an inlet end at the gases inlet and an outlet end; and a gases outlet in the lid through which a humidified flow of gases may exit the interior volume of the humidification chamber (50, 300, 400, 500), the gases outlet having an associated outlet conduit that extends between an inlet end and an outlet end at the gases outlet, wherein the lid comprises a vertical flow panel and the vertical flow panel extends downwardly from the underside of the lid (56, 456) in a central region of the lid (56, 456), characterised in that: the outlet end of the inlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a first side surface of the vertical flow panel such that the incoming gases flow enters the interior volume of the humidification chamber (50, 300, 400, 500) at that upper central region, and in that: the inlet end of the outlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a second side of the vertical flow panel. a water tub that is configured to receive a volume of water, the water tub comprising a base surface having a heater plate; a lid (56, 456) hingedly coupled to the water tub for enclosing the water tub to define the interior volume of the humidification chamber (50, 300, 400, 500) and which is movable between a closed position in which the water tub is closed by the lid (56, 456) and an open position in which the water tub is open; at least one operable clip (170, 190, 200, 210, 290, 560) provided on either the lid (56, 456) water tub which is configured to engage with a complementary catch (172, 192, 212, 312) provided on the other of the water tub or lid (56, 456), for securing the lid (56, 456) in the closed position; a gases inlet in the lid for receiving a flow of gases into the interior volume of the humidification chamber (50, 300, 400, 500), the gases inlet having an associated inlet conduit that extends between an inlet end at the gases inlet and an outlet end; and a gases outlet in the lid through which a humidified flow of gases may exit the interior volume of the humidification chamber (50, 300, 400, 500), the gases outlet having an associated outlet conduit that extends between an inlet end and an outlet end at the gases outlet, wherein the lid comprises a vertical flow panel and the vertical flow panel extends downwardly from the underside of the lid (56, 456) in a central region of the lid (56, 456), characterised in that: the outlet end of the inlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a first side surface of the vertical flow panel such that the incoming gases flow enters the interior volume of the humidification chamber (50, 300, 400, 500) at that upper central region, and in that: the inlet end of the outlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a second side of the vertical flow panel. the outlet end of the inlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a first side surface of the vertical flow panel such that the incoming gases flow enters the interior volume of the humidification chamber (50, 300, 400, 500) at that upper central region, and in that: the inlet end of the outlet conduit is located at or toward an upper central region of the interior volume of the humidification chamber (50, 300, 400, 500) and adjacent a second side of the vertical flow panel.