40 ILCS 5/6-176
A vacancy on the board owing to death, resignation or any other cause, shall be filled as follows: if the vacancy is that of an ex-officio member, the mayor of the city shall appoint a person to serve until a person qualified as hereinbefore described shall assume the duties of member of the board. If the vacancy is of an active fireman member, or a pensioner or annuitant member, the successor shall be elected to serve during the remainder of the unexpired term at a special election to be held by the board within 30 days from the date the vacancy occurs and to be conducted in the same manner as the regular annual election.
A member elected by the active firemen who resigns or is discharged from the fire service of the city shall automatically cease to be a member of the board.
Any Elective member of the board shall be subject to recall as follows:
If not less than 60% of the active firemen contributors to the fund, or not less than 60% of the pensioners and annuitants (minors under age 18 excepted), petition the board in writing to declare vacant the membership of an active fireman member or pensioner or annuitant, as the case may be, the board, within 15 days after receipt of the petition shall declare such membership vacant. A member of the board is not subject to recall more than once in any calendar year nor within one year after a previous recall petition.
40 ILCS 5/6-176