Hydrogen narcosis (also known as thehydrogen effect – a rather ambiguous term) is thepsychotropic state induced by breathinghydrogen at high partial pressures. Hydrogen narcosis produces symptoms such as hallucinations, disorientation, and confusion, which are similar tohallucinogenic drugs. It can be experienced byunderwater divers who dive to 300 m (1,000 ft) below sea level breathing hydrogen mixtures.[1] However, hydrogen has far less narcotic effect than nitrogen (which causes the better knownnitrogen narcosis) and is very rarely used in diving. In tests of the effect of hydrogen narcosis, where divers dived to 500 m (1,600 ft) with a hydrogen–helium–oxygen (hydreliox) mixture containing 49% hydrogen, it was found that while the narcotic effect of hydrogen was detectable, theneurological symptoms ofhigh-pressure nervous syndrome were only moderate.[2][3]
