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Fundamental Fireplace Facts

Natural gas, electricity, and oil are the most prevalent fuel sources for modern home heating systems. However, before these modern resources were available, the fireplace or wood stove was the sole source of heat in a home. Although the fireplace can't compete with modern heating systems as an energy and cost-efficient source of heat, the fireplace remains one of the most popular features in a home.

There are two basic styles of fireplace construction: masonry and prefabricated metal (also called zero clearance). The former set the standard for fireplace construction until the late 1970s when the latter became a popular and affordable alternative for builders and home buyers. The different fireplace styles operate in essentially the same fashion. Both have a firebox, damper, flue, and spark arrestor. Both types of fireplaces are typically outfitted with a mesh screen and glass doors.

True to its name, a masonry fireplace is custom-built of brick and mortar. The firebox is constructed of firebricks, and the flue consists of brick or a clay or terra cotta liner. Firebricks and the mortar that surrounds them are intended to withstand extreme temperatures.

On the other hand, a prefabricated metal fireplace is installed and assembled on-site. The metal box contains firebrick panels, called refractory brick panels, that line the sides, back, and bottom of the firebox. The flue for a prefabricated fireplace consists of a metal pipe that is concealed by a chimney constructed of plywood or another siding material.

In both cases, the hearth and fireplace face can be constructed of brick, stone, or another decorative finish.

Many people use a fireplace as a secondary source of heat during winter. For others, a crackling fire and the aroma that accompanies it can simply be the source of many pleasurable moments. In either case, a poorly maintained fireplace can spell disaster.

Failing to maintain your fireplace properly can lead to a chimney fire. Chimney fires occur when combustible deposits on the inner walls of the chimney ignite. These explosive deposits, called creosote, are a natural byproduct of combustion. A fire hazard exists if 1/8 to 1/4 inch of creosote (or more) coats the inner walls of the chimney, creating a time bomb waiting to go off. A chimney fire can literally level your house.

One thing stops creosote from becoming a problem: a fireplace inspection and sweeping by a professional chimney sweep at least once annually or after burning one cord of wood-whichever comes first. More frequent cleanings may be required, based on the type of wood burned, the type of appliance, and the frequency of use. In general, an older, uncertified wood stove, or any appliance that is used frequently, requires more than one cleaning per year.

Prefabricated metal fireplaces often need more frequent cleaning. They burn cooler, allowing a higher degree of condensation of combustion deposits on the interior surface of the fireplace flue.

According to the National Chimney Sweep Guild (www.ncsg.org), a national trade association comprised of chimney sweeps, a visual inspection is all that is normally required for most chimneys. In the case where a visual inspection is neither possible nor adequate, many chimney sweeps are equipped to do more elaborate inspections with a video camera and monitor referred to as a "chimscan." The chimscan is more costly than a visual inspection, but will reveal more and better information about the condition of a chimney. This is especially important when the integrity of the flue is in question due to age or damage from an earthquake or chimney fire.