All revenues received from the collection of fire service fees provided in this article shall be placed in a Fire Service Fee Fund. These funds shall be used only to defray the cost of and the continuance, maintenance, and improvement of fire protection services within the first due area of the Parsons Volunteer Fire Department as designated the State Fire Commission and the State Fire Marshal and no part of such revenues shall be used for any other municipal purpose. Any future adjustment of the rates and charges imposed by this article shall be determined by applying the same adjustments equally to all rates and charges imposed by this article.