The current invention concerns a flow rate indicator for indicating a predetermined fluid flow rate through an inhalation/exhalation device such as a spirometer, inhaler or spacer. The fluid flow rate indicator is one that generates a sound to indicate when the flow rate along the flow path is at a predetermined rate, and comprises a corrugated portion 25, (7, Fig 1) having at least one corrugation extending into the flow path. Said corrugated portion (7, Fig 1) may be provided on the body (2, Fig 1) of the inhalation/exhalation device itself between an aperture (3, Fig 1) and a mouthpiece (4, Fig 1) thereof. Alternatively it 25 may be provided on the body of a separate device 20 which provides a second fluid flow path - extending between an inlet 21 and outlet 22 thereof - and which is, in use, attached to the inhalation/exhalation device such that its outlet 22 is in communication with the fluid flow path extending through the inhalation/exhalation device. The corrugations 25 in this example extend into the second fluid flow path extending through the attachment device 20. The application also teaches a method of using such a device and a system comprising the device.
