Section 7. If the workload of the board so requires, the governor with the advice and consent of the council, may, upon request of the commissioner, recall any former member of the board to sit as a member in any conference or hearing conducted under the provisions of chapter one hundred and fifty-two. Such former member when recalled, shall be assigned to such proceedings as the commissioner shall determine, and when so recalled and assigned he shall have all the powers and duties of a member of the board. The period for which a former member may be recalled shall not exceed one year, but the governor may, upon the request of the commissioner and the advice and consent of the council, recall said member for successive one year periods. No former member of the board shall represent any person before the board during the period for which he has been recalled as a member or decide cases in which he had an interest or involvement during his absence from the board. A former member so recalled shall be paid by the commonwealth in addition to any pension or retirement allowance received by him, the amount by which the regular salary of a member of the board exceeds such pension or retirement allowance which he is entitled to receive for the period.