You mentioned in your earlier post you could smell the gas.
Natural gas has no smell,it is added.
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Well, the press and the Gas Co. were calling it a methane bubble. All I can guess is that either it is not pure methane, and some stinky odors of a different compound get released with the methane when it comes up, or we are calling the gas bubble by an incorrect name, because it is made of something other than methane entirely.