You are correct. The best you can do would be an activated carbon filter, which some better filters have. However, if I am reading/interpreting the graphs correctly, this is talking about over four miles from the leak. You'd be in the 2-5 ppm range (based on surveys) or less for NG (ethane and methane). so, maybe some reduction, but I doubt it would have a physiological effect.

That may be still in the range for mercaptan tracer gas olfaction, in which case carbon would decrease the smell, but that's about it.