GAS MIXTURES Mixed gas led to controversy when divers first started using it for deep diving by increasing the depth to which divers could now venture. Safety was questioned at depth and during decompression. Intense diving in the deep waters of caves and the sea has brought about the introduction of mixed gas diving. Nitrox - (Nitrogen, Oxygen), Trimix - (Helium, Nitrogen and Oxygen) and Heliox - (Helium, Oxygen) assists the deep divers in their ability to have sound mind and clear thinking, greatly eliminating the narcotic effects the diver had to experience while diving deep only on air (Nitrogen and Oxygen), at depths of 50 meters and beyond. Mixed gas diving does not totally eliminate the effects of narcosis. Helium at depth adds to the narcotic effects the body has to endure. Equally important are the effects of oxygen toxicity breathed at depth, oxygen could cause the diver to suffer uncontrollable seizures and sure death as a result of unconsciousness and drowning. Gas mixtures have to be mixed using caution, when analysing these gasses the slightest mistake could cost a diver his life.