Del. Code tit. 19, § 1318

An employee organization that has been certified as the exclusive representative of a bargaining unit deemed to be appropriate prior to September 23, 1994, shall so continue without the requirement of an election and certification until such time as a question concerning representation is appropriately raised under this chapter in accordance with § 1311(b) of this title, or until the Board finds the unit not to be appropriate in accordance with § 1310(f) of this title.