Mont. Code Ann. § 50-74-102

No boiler which does not conform to the rules adopted by the department governing new construction and installation shall be installed and operated in this state after 12 months from the date upon which the first rules under this chapter pertaining to new construction and installation shall have become effective unless the boiler is of special design or construction, is not covered by the rules, or is in any way inconsistent with such rules, in which case a special installation and operating permit may be granted by the department at its discretion.