Home heating equipment is the leading cause of U.S. home fires during the months of December, January, and February, when nearly half (48 percent) of all U.S. home heating equipment fires occur. January is the leading month for home heating fires; one-fifth (20 percent) of all home heating fires happen during this month.
According to NFPA’s latest heating equipment statistics, there was an annual average of 48,530 home heating fires between 2014 and 2018, resulting in an estimated 500 civilian deaths, 1,350 civilian injuries, and $1.1 billion in direct property damage. During the coldest months of the year, when we see the largest share of home heating fires, it’s critical that people understand when and where home heating fires tend to happen so that they can take the needed steps to minimize those risks.
Contributing to almost half of these fires are household fireplaces and the associated chimneys. Fireplaces have been used for centuries and are a great way to add warmth and ambiance to any home, but there will always be special considerations when using an open flame to create heat.
The purpose of this paper is to discuss household fires caused by chimneys and fireplaces and to cover key points of understanding, to include:
Most fires associated with fireplaces occur in the chimney, not in the firebox. Of these chimney fires, there are primarily three common causes. The first is creosote accumulation on the chimney wall. Creosote is created by the unburnt fuel from the smoke as it passes through the chimney. While the hot smoke passes through the chimney, it condenses on the wall of the chimney due to a difference in temperature and creates a layer of unwanted fuel-load. The creosote is a dark, tar like substance that is very susceptible to ignition.
Creosote is highly combustible and is well known for its fire threat in chimneys of wood-burning fireplaces. Creosote’s flash point (the lowest temperature at which vapors will ignite when given an ignition source like a spark or flame) in a liquid form has been reported to be as low as 165 degrees Fahrenheit (F). A spark, burning ember, or flame that raises the liquid creosote temperature to 165 degrees F can ignite the creosote in a chimney. The auto-ignition temperature of dry creosote has been reported to be 451 degrees F, which is the same as paper.
A second possible cause is from a defect in the chimney wall or pipe due to improper installation or a design flaw. It does not matter if the chimney is constructed of brick, stone, or metal; if there is a way for direct or indirect heat or flame impingement on combustibles, a fire may occur.
The third common cause of fire losses involving chimneys involves the release of embers or sparks from the chimney to surrounding combustibles inside a structure or outside, such as a roof. All combustible material (furnishings, etc.) should be at least three feet away from the opening of a fireplace.
Below are some of the potential parties that may be responsible for fireplace fires:
Others with a professional responsibility that requires due diligence include:
Most fireplaces are likely either masonry built or zero clearance. Masonry built fireplaces are usually constructed of brick or stone with fireboxes made of the same material, creating a solid barrier between the fireplace and construction materials. Typically, the firebox on masonry fireplaces has little to no metal and may or may not have doors. Zero clearance fireplaces, on the other hand, are manufactured fireboxes that are fire-rated so that no (zero) clearance is required between the firebox and construction materials like wood framing and sheetrock.
Zero clearance fireplaces are factory-built units made from sheet metal or cast iron. They are also known as prefabricated fireplaces because they come ready to install. Zero clearance fireplaces are so named because they are sufficiently insulated to be installed within close range of combustible materials, such as walls or wood framework, without requiring a masonry foundation. Many apartment and condominium complexes are constructed with a zero clearance fireplace. Some include glass doors, and some only have spark arrestor screens.
Factory-built fireplaces are tested and listed by organizations like Underwriters Laboratories (UL) and Canadian Standards Association (CSA). UL 127 covers the requirements for factory-built fireplaces. This includes the fire chamber, chimney, roof assembly, and other related parts. The National Fire Protection Association (NFPA) also regulates fireplaces via NFPA Standard for Chimneys, Fireplaces, Vents, and Solid-Fuel Burning Appliances in NFPA 211 as well as a section covering fixed blowers and other electrical accessories covered under the National Electric Code, NFPA 70.
NFPA 211 Standard for Chimneys, Fireplaces, Vents, and Solid Fuel Burning Appliances states the following:
The International Code Council (ICC) also has regulations for building codes under several of the code books including Building, Residential, Existing, Fire, and Mechanical.
The ICC Building and Residential Books devote Chapter 10 to Chimneys and Fireplaces and include a section on factory-built fireplaces. The Mechanical Code covers chimneys in Chapter 8 and governs the installation, maintenance, repair, and approval of chimneys, chimney liners, and connectors. Gas-fired appliances are covered in the code book for International Fuel Gas Code. The Fire Code has definitions in Chapter 2 and covers chimneys in Chapter 603.2:
603.2 Chimneys. Masonry chimneys shall be constructed in accordance with the International Building Code. Factory-built chimneys shall be installed in accordance with the International Mechanical Code. Metal chimneys shall be constructed and installed in accordance with NFPA 211.
The CSIA (Chimney Safety Institute of America) states that homeowners should inspect fireplaces and chimneys and should be cleaned when one eighth of an inch of sooty buildup is evident or visible inside the chimney and flue system. It also states that the chimney and fireplace should be cleaned with less than one eighth of an inch of sooty building if any glaze is visible in the firebox or chimney.
While improper design and lack of maintenance are often the causes of fires, an often-overlooked cause is improper installation, including common errors such as:
The United States Consumer Product Safety Commission (CPSC) has recalled the following fireplace inserts:
Fortunately, most heating fires can be prevented by making sure heating equipment is in good working order and monitored carefully. NFPA offers these tips and guidelines for safely heating your home during winter:
The easiest way to prevent fireplace and chimney fires, and the injuries and damages they may cause, is to adhere to basic safety practices. This includes being aware of potential defects and hazards and keeping a fire extinguisher in an easily accessible location (as well as replacing it according to the manufacturer’s instructions).
Remember— while accidental fires caused by fireplaces, chimneys, and fireplace inserts can be caused by user carelessness, fires often stem from negligent installation or a faulty product. Should you incur losses due to such a fire, hiring the right expert early in the claims process will help protect the fire site from potential spoliation and support your ability to make a successful subrogation claim.
We would like to thank Rick Anewalt, IAAI-CFI, PI, and Don Davis, CFI-IFSAC, CFEI, CVFI for providing insight and expertise that greatly assisted this research.
Don Davis is a Senior Investigator in J.S. Held’s Fire Origin & Cause Practice. Don specializes in fire and explosion scene investigations and is responsible for investigating fire and explosion incidents in commercial, residential, industrial facilities, automobiles, heavy equipment, and marine conveyances. He has more than 30 years in both public and private sectors conducting background and fire scene investigations and has testified or given depositions in Arkansas and Louisiana State Courts and Federal Court on both fire origin and cause, as well as fire code and fire spread related cases.
Don can be reached at email@example.com or +1 501 617 4517.
1. Richard Campbell (2018). NFPA’s “Home Fires Involving Heating Equipment”. Quincy, MA. National Fire Protection Association Research
2. USFA. Heating Fires in Residential Buildings (2013-2015). Retrieved from https://www.usfa.fema.gov/downloads/pdf/statistics/v18i7.pdf
3. International Code Council (2018). Fire and Mechanical, (2018). Country Club Hills, IL: International Code Council Inc. https://www.ci.independence.mo.us/userdocs/ComDev/2018%20INTL%20MECH%20CODE.pdf
4. Underwriters Laboratories (2015). Standard for Factory-built Fireplaces (UL 127). Northbrook, IL. UL LLC. https://standardscatalog.ul.com/standards/en/standard_127
5. Susan McKelvey January 15, 2021 NFPA Article on Winter Fire Safety
6. Chimney Safety Institute of America (2007) Chimney Fires: Causes, Effects & Evaluation
7. NFPA 211: Standard for Chimneys, Fireplaces, Vents and Solid Fuel Burning Appliances
8. United States Consumer Product Safety Commission. Information and photos of recalled products retrieved from www.cpsc.gov:
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