(1) Notice of appearance. Any person acting in a representative capacity on behalf of a party or participant shall file a notice of appearance with the board and shall serve a copy on all other parties. This requirement shall apply to attorneys as well as to other duly authorized representatives of parties. A person listed in a petition for review as representing petitioners need not file a notice of appearance.

(2) Substitution. In the event of a change in representative or attorney, a notice of substitution must be filed with the board and a copy served on all other parties before the change in representative shall become effective.