Solid Fuel Burning Devices
In recent years, the popularity of burning solid fuel (usually wood) as a supplemental or primary source of home heating has grown. Many people feel this gives them freedom from the oil companies and saves large amounts of money. The drawback to the burning of solid fuel in the home is that of controlling the heat output and the inherently elevated temperature the unit operates at in comparison to most furnaces. Most solid-fuel-burning devices operate at a stack or exhaust temperature well above 500 degrees F, sometimes reaching as high as 700 degrees F.
If improperly seasoned firewood is continuously used in a solid-fuel device, an accumulation of creosote can occur. Creosote is formed by the resins and moisture contained in the wood. If a device is consistently operated at a high enough temperature, the chance of creosote build-up is much less. If an abundance of creosote collects in the smoke chamber and the chimney of a solid-fuel device, the results can be catastrophic. The creosote can ignite at a temperature of about 500 degrees F. Once ignited, the creosote can create stack temperatures of over 2,000 degrees F. This temperature can deteriorate chimney components and cause excessive conducted heat. Many house fires have been caused by the build-up and ignition of creosote in solid-fuel chimney systems.
Another issue with solid-fuel-burning devices is the proper installation of the device and chimney system. Many devices allow for direct contact with combustible materials to take place. For the unit to be rated as “zero clearance to combustible items,” most manufacturers require a free air space around the unit to achieve this rating. Nearly all chimney systems require a 2-inch clearance to any combustible material including building insulation. The CABO one- and two-family building code requires a 2-inch clearance between any combustible building material and all masonry chimneys.
One of the leading issues concerning the use and installation of solid-fuel-burning devices is the installation of building insulation material in proximity or in contact with some portion of the system. The chimney pipe and the device depend on air circulation to cool. If the unit is in any way covered with building insulation, the effectiveness of airflow is reduced. With the reduced airflow—which results in higher operating temperatures—the potential for ignition of ordinary combustibles is greatly increased. Many instances have been documented where the insulation installer has failed to provide proper blocking around all heat-producing devices.
The fire investigators at Donan Engineering are extremely experienced in the assessment of solid-fuel-burning devices and their installation. With the availability of structural and mechanical engineers, the failure mode involved in solid-fuel-burning device fires can be easily and quickly identified.