Each city of the first class with a population in excess of forty-one thousand inhabitants as determined by the most recent federal decennial census or the most recent revised certified count by the United States Bureau of the Census shall employ a full-time fire chief with appropriate training, credentials, and experience and for whom firefighting or emergency medical first response is a full-time career. The fire chief shall be appointed under the Civil Service Act by the mayor with the approval of the city council or by the city manager in cities that have adopted the city manager plan of government. The fire chief shall have the immediate superintendence of the fire prevention, fire suppression, and emergency medical first response services and the facilities and equipment related to such services of the city. The fire chief shall promulgate, implement, and enforce rules governing the actions and conduct of volunteer members of the department so as to be in conformity with the personnel policies of the city.