Section 21(9) in The Static and Mobile Pressure Vessels (Unfired) Rules, 2016
(9)Notwithstanding anything contained in sub-rules(1) to (8) above, vessels for storage of liquified petroleum gas and other liquefied compressed gases, can be placed underground or covered by earth (mound) conforming to the national or international standard accepted by the Chief Controller and the requirements specified in Schedule III.
