Tis the Season for Chimney Fires

 

By Marge Padgitt

Chimney Fire: Source: Marlboro FD, VA

It’s that time of year again – the season for chimney fires. As a chimney and fireplace service company we see the results of the lack of proper maintenance and improper installation that can cause fires and destruction of property, and in some cases injury or death. Chimney fires are preventable and should be avoided because of the risk that they could escape the chimney and catch the house on fire.  

All types of wood – even hardwood- creates creosote when burned. It accumulates on flue and smoke chamber walls and must be periodically removed. Chimney sweeping should be done by a professional chimney sweep who has the proper equipment to do the job right. First, tarps and a vacuum are set up. Then the sweep brushes the flue with wire brushes for masonry flues, or poly brushes for metal flues, and removes the creosote from the flue and fireplace or wood stove. Next, the sweep should run a chimney camera through the chamber and flue to inspect it and make sure there are no broken flue tiles, missing mortar, or blockages, or in the case of a manufactured fireplace or stove, that all of the metal pipe seams are solid and unwarped. The chimney sweep will then do a visual inspection of the interior and exterior chimney, check for proper clearance to combustibles and proper installation of components, then provide a report on its condition.

Chimney sweep  Source: Adobestock.com

It is very common for repair issues to arise with any type of chimney. Regular maintenance is
needed in order to keep the system functioning properly. Exterior masonry repairs should be done in the spring or summer, but if the chimney needs a new flue liner this can be done any time of year. Chimney fires can cause costly damage to a masonry or metal chimney system. If relining is necessary, it will cost thousands of dollars. Fortunately, chimney fires are covered by homeowner’s insurance. However, it is best to avoid a chimney fire in the first place.  

According to the U.S. Fire Administration there were 83,300 house fires caused by heating in 2018.  The National Fire Protection Association’s latest press release dated November 22, 2010 estimates that 66,100 home fires caused 1.1 billion in property damage, 1,660 injuries and 480 deaths in 2008, which was a 0.5% decline from 2007.  15,200 (23%) of all home heating fires are creosote fires, which the NFPA calls “failure to clean” fires that were confined to a chimney or flue, or involved solid-fueled space heaters, chimneys, connectors, and fireplaces.  See the entire news release at www.nfpa.org

Tips:

1.       Never burn a dry Christmas tree in a fireplace.

2.       Only burn dry, seasoned hard or soft cordwood in a stove or fireplace

3.       Only burn one piece of hedge to two pieces of other types of wood.

4.       Have the chimney inspected and swept annually, or twice per season if using a wood stove.

5.       Have a Draw Collar installed for hard-starting wood stoves.

6.       When purchasing a new home have the chimney inspected by a CSIA Certified Chimney Sweep prior to closing so you know what you are getting into.

7.       If you hear a whooshing sound, or freight-train like sound, or the room fills with smoke, get out of the house and call the fire department. Go outside and see if flames are shooting out the top of the flue.

 

See more information about chimney and fireplace maintenance and how to choose an appliance in Marge and Gene Padgitt’s new book Wood-Fired Heating and Cooking: How to choose, maintain, and operate a wood-burning appliance at Amazon.com or hearthmasters.net.

How to Avoid a Chimney Fire that Can Lead to a House Fire

House fire caused by flammable
creosote and improper construction

Creosote is a flammable substance that must be removed from the flue and smoke chamber periodically in order to avoid having a chimney fire. 

Since all wood creates creosote, including dry hardwoods, creosote is impossible to avoid when burning wood in a fireplace, wood-burning stove, circulating fireplace, or stove insert.

Creosote can only be removed by brushing the flue and chamber out with wire or poly brushes that are made especially for this purpose. Professional chimney sweeps know what size and type of brush to use for the type of flue system installed. There are many different types of venting systems, so knowing how to properly maintain each type is critical.

In a masonry chimney with a wood-burning fireplace the most common type of flue system is made out of vitreous clay tile, and the smoke chamber is usually made out of brick, stone, or block. This type of venting system accumulates more creosote than a stainless steel flue liner does because it is more porous.

Stainless steel flue liners don't accumulate as much creosote if they are properly insulated and installed correctly, but can be damaged by a chimney fire so maintenance is necessary.

Smoke chambers that are not parge coated with insulating mortar per IRC Code requirements allow more creosote accumulation due to their rough surfaces and corbels which decrease the flow of smoke and tar vapours.

The National Fire Protection Association and the National Chimney Sweep Guild recommend that creosote be removed after 1/8" accumulation on flue walls.

Gene Padgitt Sweeping a masonry chimney

The creosote being removed should be stage 1 which is very light and ash-like, or stage 2 which is more dense. If there is any accumulation of stage 3 glazed baked-on tar-like creosote, something is not right with the system, the fuel being used, or the operation of the appliance. Stage 3 creosote is the most flammable type, and is most often associated with chimney fires.

A chimney fire occurs when a spark ignites the flammable creosote, usually in the smoke chamber just above the damper, and flame may spread through the remaining fuel source (creosote) on the flue walls.

Stage 3 Creosote on flue walls

Chimney fires can be of short or long duration, but almost always cause damage to the smoke chamber and flue liner due to the quick temperature differential that occurs to the masonry during a chimney fire. Damages may occur to the face wall above the fireplace opening inside the house, to the back wall of the chimney, or to the top portion of the chimney and cement cap due to expansion. Fresh breaks may be found in the masonry and cement cap in a masonry chimney.

Burnt creosote that has been on fire

In a manufactured fireplace and metal chimney damages may occur to the metal smoke chamber and metal chimney pipe in the form of buckling, warping, and opening of seams. With a Class A chimney system serving a wood-burning stove, the same type of damage can occur.

In either case, the damage must be repaired, or parts replaced before further use because the system is no longer functional if it has damages.

Unfortunately, most chimney fire damage is found only during inspection of the system during routine chimney cleaning/inspection maintenance by a professional chimney sweep. Most chimney fires go unnoticed by homeowners when the fire occurs because they either don't recognize the whoosh of air and increased draft during a chimney fire, or are out of the room when it occurs and the fires goes out before they return.

Burnt, honeycomb creosote that has
been burned in a chimney fire

After a fire has damaged a chimney system, the flue liner and chamber may have cracks and gaps that would allow a second fire to escape to nearby combustible wood framing. This is how a house fire due to chimney fire commonly occurs. Another way a house fire can occur is if flame and sparks shooting out the top of the chimney catch the roof on fire.

chimney inspection with a Chim-Scan Camera

Water damage from rain and condensing acidic flue gasses often causes mortar joints between tile liner sections to deteriorate and leave gaps, which may also allow heat and flame to escape the flue system and cause a house fire.

The only way to know if the flue system has damages is to sweep it first to remove creosote, then run a special chimney camera through the chamber and flue. Photos may be taken with this type of camera. If damages are found, do not use the appliance until it is properly repaired by a professional chimney contractor.
 

Break in clay tile flue liner

In the greater Kansas City area, call HearthMasters, Inc. for chimney maintenance, repair, and building.  

www.chimkc.com

816-461-3665