Section 3. The state fire marshal, or his successor, shall be appointed by the Massachusetts fire service commission, established in section one hundred and sixty-five B of chapter six and shall serve at the pleasure of said commission. The position of state fire marshal shall be classified in accordance with section forty-five of chapter thirty and the salary shall be determined in accordance with section forty-six C of said chapter thirty and the state fire marshal shall devote his full time during business hours to the duties of his office.