Every building hereafter erected and also every existing building not
now supplied from some outside source with illuminating and heating gas, to
which a gas connection may hereafter be run from such outside source, shall
have a conveniently accessible stopcock or other suitable device fixed to
the supply pipe leading into the building at a place between the sidewalk
line and the line of the curb of the street from which said supply pipe is
run, so arranged as to allow the supply to be shut off; provided, however,
that where any building is situated at a distance of more than 100 feet from
the street from which such supply pipe is run, said stopcock or other suitable
device may be situated inside the curb of said street but not less than 30
feet from such building. Such stopcock or other device shall be so marked
as to indicate the contents and purpose of the supply pipe to which it is
attached.