Miss. Code § 75-57-33
No cylinder installation shall be made unless the cylinders are designed, fabricated, tested and marked in accordance with the regulations of the United States Department of Transportation or the United States Interstate Commerce Commission, and constructed for a designed pressure of not less than two hundred forty (240) pounds per square inch. Cylinders with a water capacity of less than two hundred fifty (250) pounds shall be charged by weight with liquefied petroleum gas only at bulk storage or cylinder filling plants and not from mobile units such as delivery trucks, except cylinders installed as part of a system burning liquefied petroleum gas or compressed natural gas as a motor fuel or for farming purposes such as in flame cultivators or hot air balloon cylinders. Cylinders with a water capacity of two hundred fifty (250) pounds or larger may be charged at the installation from mobile units, provided they are equipped with a fixed liquid level gauging device and a filling valve, which is designed in accordance with the national standards and codes, in addition to other required or acceptable valves and fittings. Cylinders with a water capacity of two hundred fifty (250) pounds or larger, in addition to having all the necessary valves and fittings, must be installed permanently in accordance with the national standard and codes.
Miss. Code § 75-57-33