Fire insurance key rates in Texas range from $.09 to $1.00 based upon the adequacy and pressure of the water supply, and the quality of fire fighters and their equipment. Effective 01/01/98, Texas is rated in accordance with the national board class ratings published by the National Insurance Service Office (ISO). New ratings are based upon 2-10 rating systems. Denison is rated Class 3. Visit the Fire Department page on the City of Denison website.