high helium content of natural gas is accompanied by high contents of nitrogen and carbon dioxide. the percentage of nitrogen is usually 10 to 20 times that of helium, so that natural gas with 5 percent or more helium may have little or no methane. a representative sample from the pinta dome in apache county, arizona, for instance, has 8.3 percent helium, 89.9 percent nitrogen, 1 percent carbon dioxide, and only 0.1 percent methane. in such cases, the gas is produced solely for its helium content.