A series of tests was conducted in five instrumented chimneys to study the intensity and duration of chimney fires due to the ignition and burning of combustible desposits accumulated on chimney linings over a prolonged period of time. These tests were conducted: (1) to establish typical conditions including temperatures in the chimneys and on combustible surfaces nearby, and (2) to determine the duration of the burnout as evidenced by elevated temperatures within the chimney. The results of these point out some areas where the codes and standards covering residential wood heating appliances should be updated to better protect against failure due to chimney fires.