 Except for helium and probably neon , all gases that can be breathed have a narcotic effect , although widely varying in degree . The effect is consistently greater for gases with a higher lipid solubility , and there is good evidence that the two properties are mechanistically related . As depth increases , the mental impairment may become hazardous . Divers can learn to cope with some of the effects of narcosis , but it is impossible to develop a tolerance . Narcosis affects all divers , although susceptibility varies widely from dive to dive , and between individuals . 
