To the extent permitted by statute, where the application of a State Liquefied Petroleum Gas Board Code rule would be unreasonable under the facts of the particular case, and safety may be obtained in other ways, the Liquefied Petroleum Gas Board may, upon adequate showing by the person affected, grant exemption or modification of the rule complained of under such requirements as will secure a reasonable condition of safety, provided such exemption or modification be not in conflict with the law.