Mich. Comp. Laws § 123.842

Sec. 2. The provisions of section 1 shall not apply (a) To the chief officer or the assistant chief officer in command of the fire department of a municipality. (b) To employees of a fire department who are employed subject to call. (c) To the members or employees of a fire department when required to remain on duty by the chief officer of such department, his aides or assistants, in cases of public necessity arising from great conflagration, riot, flood, epidemic of pestilence, or disease, necessary absence of regularly employed men due to military service, or for disciplinary measures. (d) To the members of any volunteer fire department. (e) To any municipality which, by agreement with the collective bargaining agent representing affected employees, does not require its employees engaged in fire fighting or subject to the hazards thereof, to be on duty more than 40 hours in any consecutive 7-day period.