Abstract: Device for use with an inhaler, the inhaler having a body, an aerosol canister arranged in the body containing medicament, including a metered dose chamber and able to dispense a metered dose of the medicament, a nozzle in fluid communication with the canister, an opening for dispensing of the medicament in fluid communication with the nozzle. The device includes elements for activating the canister to open and dispense the medicament in response to an airflow in the inhaler caused by inhalation of a user through the opening, return elements for deactivating the canister to close it, characterized in that the return elements deactivate the canister when the airflow drops below a certain threshold value.