The combustion of natural gas produces mainly water vapor and CO2 in small quantities. It is the fuel that generates the greenhouse gas fraction, 30% to 50% less CO2 emissions than the other fuels.
Since you are told that fossil energies, it does not pollute (little?)!
Another sentence:
According to the Life Cycle Assessment (LCA) approach, natural gas heating emits almost 3 less CO2 than any new electric heater installed.
I think they do not miss air at GrDF
The scan of this mail: