Vacancies on a board of fire commissioners shall occur as provided in chapter 42.12 RCW. In addition, if a fire commissioner is absent from the district for three consecutive regularly scheduled meetings unless by permission of the board, the office shall be declared vacant by the board of commissioners. However, such an action shall not be taken unless the commissioner is notified by mail after two consecutive unexcused absences that the position will be declared vacant if the commissioner is absent without being excused from the next regularly scheduled meeting. Vacancies on a board of fire commissioners shall be filled as provided in chapter 42.12 RCW.