On October 23, 1998, about 1554 eastern daylight time, a Cessna 172N, N5918E, registered to Flight School of Gwinnett, Inc., caught fire and burned on the taxiway at Gwinnett County-Briscoe Field, Lawrenceville, Georgia, while on a Title 14 CFR Part 91 flight. Visual meteorological conditions prevailed and no flight plan was filed. The airplane was destroyed by fire. The private-rated pilot reported no injuries. The flight was originating at the time. The pilot stated that after engine start, he received tower instructions to taxi and hold short of runway 25. He stated that while holding short in the run-up area, he felt heat from the left side of the floorboard, and rechecked that his cabin heater control was off. He looked at the left side interior kick panel and discovered flames from the floorboard to about 18 inches up the panel. The pilot shut the engine down using his mixture control and magneto switch, evacuated the airplane from the right side door, ran to an adjacent aircraft waiting for takeoff, and asked the pilot to report the fire to the tower. The pilot stated that the fixed-base operator manager told him the interior post light was inoperative. He further stated he was not a smoker. Subsequent investigation by FAA personnel did not reveal a positive ignition source. Reference to Cessna 172 aircraft diagrams shows fuel lines are routed close to the area that the pilot first noticed heat and flames. The airplane had undergone a recent 100-hour inspection on October 19, 1998, and a new navigation/communication radio was installed at that time. The airplane had accumulated 13.5 hours since that inspection. There was no fire extinguisher installed in the aircraft. Title 14 CFR Part 91.513 states, "At least one hand fire extinguisher must be provided and located on or near the flight deck in a place that is readily accessible to the flight crew." The airport does not have its own dedicated firefighting force, and instead, depends on a municipal firefighting capability located about 3 miles from the airport. The response time for the first fire unit to arrive at the scene was about 10 minutes. The tower personnel stated they thought the response time was acceptable, given the time of day and the traffic.