<p>➀ Researchers from Fraunhofer have developed sensor systems and measuring equipment to detect leaks in hydrogen lines and tanks.</p><p>➁ The ultrasonic sensor utilizes the photoacoustic effect to detect hydrogen leaks and can also identify small traces of other substances.</p><p>➂ A laser spectrometer and Raman spectroscopy are used for remote detection of ammonia and selective detection of hydrogen respectively.</p>