Abstract: A fuel cell system having at least one fuel cell with an external surface; and one or more of audio, image, or strain sensors external to the fuel cell surface, configured for detecting a change in the external surface of the fuel cell indicative of a fault condition. The at last one sensor may include a visual camera, an IR camera, an IR detector, or a UV-responsive camera, or an ultrasound transducer, a piezoelectric sensor and a vibration sensor, or a surface acoustic wave detector, or a mass spectrometer.

Abstract: A larynx replacement for installation in a patient's trachea comprises an air passage controlled by a valve. The valve is gas operated and sensing means are provided for detecting the presence of food or liquid in the patient's throat to close the valve, and in this way to prevent the passage of food or liquid beyond the replacement larynx.