A nebulizer (1) comprises one or more removable components (5,7,9,13), for example a mesh assembly (9), mouthpiece, plunger assembly (7) and medication chamber (13), each having an associated data carrier (5a, 7a, 9a). The data carrier (5a, 7a, 9a) can be used to store information indicating the type of removable component (5,7,9,13) that is fitted to the nebulizer (1). A removable component (5,7,9,13) may be from a set of such removable components. For example, a mouthpiece (5) fitted to the nebulizer (1) may be from a set of mouthpieces having different flow rates. The data carrier (5a, 7a, 9a) may also be used to control operation of the nebulizer (1). A data carrier (9a) attached to a mesh (9) may be used to prevent the nebulizer (1) from being used when the mesh (9) has been used a predetermined number of times.
