Me. Rev. Stat. tit. 32, § 15114

It is unlawful for any person, firm, partnership or corporation to operate under pressure in this State a boiler or pressure vessel to which this chapter applies without a valid inspection certificate as provided in this chapter. The operation of a boiler or pressure vessel without an inspection certificate constitutes a Class E crime on the part of the owner or user of the boiler or pressure vessel and is punishable by a fine of not more than $100 or by imprisonment for not more than 30 days, or by both.