Michigan Compiled Laws, Chapter 324. Natural Resources and Environmental Protection § 324.5527

Sec. 5527. (1) As used in this section, “emergency” means a situation arising from sudden and reasonably unforeseeable events beyond the control of the source, including acts of God, war, strike, riot, catastrophe, or other condition as to which negligence on the part of the person was not the proximate cause, that requires immediate corrective action to restore normal operation, and that causes the source to exceed a technology-based emission limitation contained in an operating permit issued pursuant to section 5506,  1a permit to install or permit to operate issued pursuant to section 5505, 2or any rule promulgated under this part due to unavoidable increases in emissions attributable to the situation. An emergency does not include acts of noncompliance caused by improperly designed equipment, lack of preventative maintenance, careless or improper operation, or operator error.

(2) An emergency constitutes an affirmative defense to an action brought for noncompliance with a technology-based emission limitation contained in an operating permit issued pursuant to section 5506, a permit to install or permit to operate issued pursuant to section 5505, or any rule promulgated under this part if the emergency is demonstrated through properly signed, contemporaneous operating logs, or other relevant evidence that establishes all of the following:

(3) In any enforcement proceeding, the defendant seeking to establish the occurrence of an emergency has the burden of proof.