35 ILCS 200/6-30
In counties not under township organization with less than 3,000,000 inhabitants in which no board of review is elected under Section 6-35, the board of county commissioners shall constitute the board of review. They shall have all the powers and perform all the duties conferred on or required by boards of review. County commissioners shall receive no additional compensation for serving on the board of review. County commissioners serving as the board of review must meet the examination requirements of Section 6-32. If any member of the board of county commissioners fails to meet the examination requirements, the board of county commissioners shall appoint a board of review. Members of the county commissioners who meet the requirements of Section 6-32 may serve on the appointed board of review, but shall not receive additional compensation.
The board of county commissioners shall appoint a 3-member board of review if (i) the board of county commissioners so chooses or (ii) any member of the board of county commissioners fails to meet the examination requirements of Section 6-32. No person may serve on an appointed board of review under this Section unless he or she meets the examination requirements of Section 6-32. Members of a board of review appointed by the board of county commissioners shall receive a per diem for their services as established by the board of county commissioners.
A board of review appointed by the board of county commissioners shall serve at the pleasure of the board of the county commissioners. If the board of review is appointed because any member of the board of county commissioners fails to meet the examination requirements of Section 6-32 and all members subsequently fulfill the requirements, the board of county commissioners may terminate the authority of the sitting board of review, as soon as it completes its work for a tax year, and serve as the board of review.
35 ILCS 200/6-30