(1) The commission, after hearing upon reasonable notice to all interested parties, shall decide, in each application for certification as an exclusive bargaining representative, the unit appropriate for certification. In determining the new units or modifications of existing units, the commission must consider: The duties, skills, and working conditions of the employees; the history of collective bargaining; the extent of organization among the employees; the desires of the employees; and the avoidance of excessive fragmentation. However, a unit is not appropriate if it includes:
(a) Both supervisors and nonsupervisory employees. A unit that includes only supervisors may be considered appropriate if a majority of the supervisory employees indicates by vote that they desire to be included in such a unit;
(b) Both house of representatives and senate employees;
(c) Both partisan and nonpartisan employees;
(d) Employees of the majority party caucus and the minority party caucus, unless a majority of the employees of each caucus indicate by vote that they desire to be included together in the same unit; or
(e) Employees of the legislative service center, office of legislative support services, and the office of the code reviser, in any combination with each other or in any combination with employees of the house of representatives or employees of the senate.
(2) If a single employee organization is the exclusive bargaining representative for two or more units, upon petition by the employee organization, the units may be consolidated into a single larger unit if the commission considers the larger unit to be appropriate. If consolidation is appropriate, the commission shall certify the employee organization as the exclusive bargaining representative of the new unit.