49 CFR §192.353

1. (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.
2. (b)Each service regulator installed within a building must be located as near as practical to the point of service line entrance.
3. (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.
4. (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.