The mayor of the city, acting by and through the chief of the fire department, is authorized to dispatch and use the fire apparatus and equipment of the city, together with the fire department personnel operating the same, outside of the corporate limits of the city, for the purpose of rendering assistance to neighboring communities and areas in the event of a threatening conflagration or other dire emergency. Under no circumstances shall such fire apparatus and equipment be dispatched outside of the city to such an extent as to deplete existing available equipment or leave the city without adequate fire protection.