(a) If within 30 days of the filing of an order or decision no petition for reconsideration has been filed, and no reconsideration has been ordered on the Appeals Board's own motion, the order or decision is a final order of the Appeals Board and not subject to review by any court or agency.

(b) Any petition for reconsideration shall be deemed to have been denied by the Appeals Board if it is not acted upon within 45 days of service and the order or decision is a final order of the Appeals Board and not subject to review by any court or agency. The Appeals Board may, however, upon a showing of good cause, extend the time within which it may act upon the petition for a period not exceeding 15 days.