The International Organization for Standardization (ISO) Standard 9703-1 addresses only visual aspects of alarms and defines alarm categories and visual indicators and degrees of urgency. The approach taken is to limit the proliferation of different alarms in order to avoid confusion and minimize the distraction of hospital staff not directly responsible for devices that are in the alarmed condition. ISO 9703-2 addresses auditory alarms. The purpose is to specify the auditory component of alarm signals to be used to draw attention to the fact that the medical device has detected a disturbance and to indicate the degree of urgency. Some of the criteria considered during development of the sounds include optimal signal recognition in a relatively noisy environment, maximum transmission of information at the lowest practicable sound pressure level, ease of learning and retention by operators who have to respond to the various signals, and perceived urgency of the sounds. ISO 9703-3 deals with the allocation of alarm principles. To allocate a priority to a particular alarm it is necessary to evaluate the risk to the patient of the event that the alarm indicates. A Joint Working Group of ISO and IEC is considering the application of similar principles to all medical devices with a view to consideration in the upcoming third edition of IEC 60601-1, Medical Electrical Equipment — Part 1 - General Requirements for safety.