Efficiency at sorting cards in air and  a 20 per cent oxygenhelium mixture at depths down to 100 feet and in enriched air.
D000293:Adolescent; D000328:Adult; D004242:Diving; D006371:Helium; D006801:Humans; D008297:Male; D008606:Mental Processes; D008875:Middle Aged; D010100:Oxygen; D012119:Respiration
D006371:Helium; D010100:Oxygen