In the event of the unavailability or incapacity of the appropriate staff officer or his or her successor during emergency conditions, authority to effect temporary appointments of such additional officers and employees, to classify and allocate positions to their proper grades, to issue travel orders, and to effect emergency purchases of supplies, equipment and services shall be exercised by the respective Regional Directors, their deputies, or staff in line of succession, as may be required for the discharge of the lawful duties of the respective offices.