All boilers and pressure vessels must be constructed in accordance with the ASME code, as adopted by 20 CAR § 880-701 and registered with the National Board of Boiler and Pressure Vessel Inspectors, except for those vessels stamped “UM” pursuant to U-1 and UG-115 of Section VIII-Division 1 of the ASME code as adopted by 20 CAR § 880-701, and air vessels of twelve gallons (12 gals.) or less containing one hundred fifty pounds per square inch (150 psi) or less as exempted by Arkansas Code § 20-23-102(a)(2).