Additional municipalities within the state may join the system, as provided in sections 2981 through 2985 of this title, and shall be received as members subject to the approval of the board of directors. Municipalities which do not have active fire departments may be admitted as members upon such conditions as the board of directors may fix. Private fire departments within the state may also be accepted by the board of directors as members, with equal voting rights under such arrangements as are mutually agreed upon. A municipality or private fire department may, by vote of its governing board, withdraw from the system but the withdrawal shall not be effective until ninety days after written notice of the withdrawal shall have been delivered to one of the officers of the system. (1967, No. 255 (Adj. Sess.), § 9, eff. Feb. 20, 1968.)