49. In this Part—
“gas” means any substance which is in a gaseous state at a temperature of 15°C and a pressure of 1013.25 millibars and—
consists wholly or mainly of methane, ethane, propane, butane, hydrogen or carbon monoxide; or
is specified in an order made by the Department; or
consists wholly or mainly of—
a mixture of two or more substances falling within paragraph (a) or (b); or
a combustible mixture of one or more such substances and air.
“in”, in a context referring to a pipe-line or a length thereof or works or operations in land, includes a reference to a pipe-line, length, works or operations under, over, across, along or upon it;
“owner”
in relation to any land, means a person, other than a mortgagee not in possession, who is for the time being entitled to dispose of the fee simple of the land, whether in possession or in reversion, and includes also a person holding or entitled to the rents and profits of the land under a lease or agreement the unexpired term of which exceeds 3 years;
in relation to a pipe-line, means the person in whom the pipe-line is vested;
in relation to a structure, means a person who, in relation to land being the site of the structure, is an owner thereof by virtue of paragraph (a) of this definition.