Beland, Dr. Bernard. Fire Places and Chimneys as Fire Causes. Fire and Arson Investigator. March, 1983.

Abstract: This article discusses how insulation of the walls of a chimney or fireplace could become a fire cause. Masonry brick in fireplaces or chimneys acts as a natural insulator. The heat builds and eventually the walls will reach equilibrium. This means that the heat has reached the outside surface of the wall and will be dissipated into the air. If this heat is not allowed to escape because of another source of insulation other than the brick, the walls will reach very high temperatures, capable of igniting surrounding combustibles.

An airspace is required by chimney codes to prevent this build-up of heat. The standard requirement for a chimney is four inches of brick with two inches of airspace. The back of a fireplace is usually required to be eight inches thick with four inches of airspace. This airspace is the area between the masonry brick and combustible materials. This allows the heat to escape. When combustible materials are located near chimneys, insulation should not be used.

For more information, contact:
International Association of Arson Investigators (IAAI)
300 Broadway Suite 100
St. Louis, MO 63102-2808
Phone: 314-621-1966