Manufacturers impregnate chimney sweep logs with chemicals that help break down the tar and creosote inside of the chimney that can cause a fire. When a homeowner burns the log, the chemicals rise with the smoke and cling to the creosote and tar. Over time, these chemicals soften the deposits in the chimney.
Chimney sweep logs can diminish creosote, but homeowners should not use them as a substitute for chimney cleaning. Manufacturers state that these logs can remove up to 60 percent of the creosote, so without manual cleaning the chimney still could represent a fire hazard. A U.S. Federal court found that manufacturers could not label these logs as a "chimney cleaning logs" or claim that the logs prevent chimney fires. Also, if the chimney sweep log removes the creosote, the creosote either burns up promptly to create an immediate fire hazard or falls onto the smoke shelf where it can later catch on fire.
Chimney sweeping logs are compatible with wood-burning devices including traditional fireplaces, fireplace inserts and gas fireplaces. They also work with wood and coal stoves, wood and oil boilers and straight wood furnaces. They are compatible with all flue pipes, including masonry flues, as well as catalytic converters. However, chimney sweeping logs are not compatible with barbeques, electrical appliances, gas logs, and oil and pellet stoves.
The number of chimney sweeping logs needed per season differs depending on how frequently the homeowner uses the fireplace. For homeowners who only light a fire on the weekend, burning one chimney sweeping log at the beginning or in the middle of the season is sufficient. Homeowners lighting a fire every day should use two logs, one at the beginning and one in the middle of the season. Those choosing to have a continuously lit fire should use one chimney sweeping log every two months to prevent creosote buildup.
Manual cleaning without chemicals by a professional can usually remove all of the tar and creosote within a chimney. However, if no one has cleaned the chimney regularly, the chimney can have hard, glazed deposits of tar and creosote inside. In these cases, a professional chimney sweep applies chemicals to soften the deposits and then follows the chemical treatment with further manual cleaning.