A gas installation that is wholly or partly above ground and that is used for one or more of the following: compression, distribution, separation, shutting off, regulation of gas pressure, filtration, measurement, adding of odor to gas, or any other operation required for the purpose of transferring gas in the transmission and distribution systems, other than gas installations that are underground and that are connected to such a installation, and other than such a installation where the part that is above ground is the shutter or meter only.