49 CFR 192.353
Customer meters and regulators: Location.
(a)Each meter and service regulator, whether inside or outside a building, must be installed in a readily accessible location and be protected from corrosion and other damage, including, if installed outside a building, vehicular damage that may be anticipated. However, the upstream regulator in a series may be buried.#
(b)Each service regulator installed within a building must be located as near as practical to the point of service line entrance.#
(c)Each meter installed within a building must be located in a ventilated place and not less than 3 feet (914 millimeters) from any source of ignition or any source of heat which might damage the meter.#
(d)Where feasible, the upstream regulator in a series must be located outside the building, unless it is located in a separate metering or regulating building.#