The commission shall decide in each case, to insure public employees the full benefit of their right to self-organization, to collective bargaining and otherwise to effectuate the policies of this act, the unit appropriate for the purposes of collective bargaining as provided in section 9e of Act No. 176 of the Public Acts of 1939, as amended, being section 423.9e of the Michigan Compiled Laws: Provided, That in any fire department, or any department in whole or part engaged in, or having the responsibility of, fire fighting, no person subordinate to a fire commission, fire commissioner, safety director, or other similar administrative agency or administrator, shall be deemed to be a supervisor.