A holding chamber for use with a pressurized metered dose inhaler, wherein said holding chamber is configured to enclose and carry said MDI, said holding chamber comprising: a first housing component comprising a user interface comprising an outlet opening; a second housing component comprising an inlet opening through which at least a portion of the MDI is insertable, said inlet opening being spaced apart from the outlet opening of the first housing component, wherein the first housing component is pivotally connected to the second housing component about a pivot axis, wherein the first and second housing components (8, 10) are pivotable relative to each other about the pivot axis between a closed configuration, wherein the first and second housing components define an enclosed interior space that is adapted to house and store the MDI, and an open configuration, wherein the first and second housing components are spaced apart and define an access opening communicating with the interior space so as to provide access to the stored MDI; and said holding chamber being characterised by: a cap pivotally connected to one of the first and second housing components (8, 10), wherein the cap is moveable between a closed position, wherein the cap covers the user interface, engages the other of the first and second housing component (8, 10) and maintains the first and second housing components (8, 10) in the closed configuration, and an open position, wherein the cap exposes the user interface and is disengaged from the other of the first and second housing component (8, 10) such that the first and second housing components (8, 10) are capable of being pivoted to the open configuration. a first housing component comprising a user interface comprising an outlet opening; a second housing component comprising an inlet opening through which at least a portion of the MDI is insertable, said inlet opening being spaced apart from the outlet opening of the first housing component, wherein the first housing component is pivotally connected to the second housing component about a pivot axis, wherein the first and second housing components (8, 10) are pivotable relative to each other about the pivot axis between a closed configuration, wherein the first and second housing components define an enclosed interior space that is adapted to house and store the MDI, and an open configuration, wherein the first and second housing components are spaced apart and define an access opening communicating with the interior space so as to provide access to the stored MDI; and said holding chamber being characterised by: a cap pivotally connected to one of the first and second housing components (8, 10), wherein the cap is moveable between a closed position, wherein the cap covers the user interface, engages the other of the first and second housing component (8, 10) and maintains the first and second housing components (8, 10) in the closed configuration, and an open position, wherein the cap exposes the user interface and is disengaged from the other of the first and second housing component (8, 10) such that the first and second housing components (8, 10) are capable of being pivoted to the open configuration. a cap pivotally connected to one of the first and second housing components (8, 10), wherein the cap is moveable between a closed position, wherein the cap covers the user interface, engages the other of the first and second housing component (8, 10) and maintains the first and second housing components (8, 10) in the closed configuration, and an open position, wherein the cap exposes the user interface and is disengaged from the other of the first and second housing component (8, 10) such that the first and second housing components (8, 10) are capable of being pivoted to the open configuration.