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The Home Depot

3 Dangers of Blocked Chimneys

Pro Referral > Home Guides > Fireplace & Chimney > 3 Dangers of Blocked Chimneys
3 Dangers of Blocked Chimneys

The main function of a chimney is to provide an outlet for the smoke and gases produced in the fireplace or wood stove. When the chimney is not cleaned thoroughly and regularly, it can lead to a host of problems. Some of the issues arising from blocked chimneys can prove dangerous to your home and your well-being. Thus, you should be aware of these and preventive measures that can be taken to avoid these situations. An annual cleaning and inspection of the chimney should help keep such problems at bay.


In some regions, periodic inspections may be conducted by the local zoning or building commission to ensure that the chimneys in residences are fully functional and comply with fire safety standards. Doing this helps ensure the safety of your home as well as the neighborhood that you live in.


A chimney often becomes blocked due to the accumulation of creosote inside it. Creosote is formed when the smoke from the fireplace moves through the chimney and becomes condensed over time. It can be black or brown in appearance and can be seen as a solid or flaky crust.

  1. 1.Fire

    Fire is one of the common dangers of a blocked chimney. This is because creosote is highly flammable and can burn slowly giving you no indication of what is going on. Sometimes the fire can cause a loud explosion and lead to flames shooting out of the chimney. If either of these happens then you should immediately contact the fire department. Attempting to handle the fire on your own might result in a bad situation turning worse.

  2. 2.Carbon Monoxide

    “Fire is one of the common dangers of a blocked chimney. This is because creosote is highly flammable and can burn slowly giving you no indication of what is going on.”

    This is a life-threatening danger of blocked chimneys and can could catch you and your family off guard. It is estimated that hundreds of deaths occur every year due to carbon monoxide poisoning in the United States annually. The characteristics of carbon monoxide gas are that it is invisible, odorless, and tasteless. It is produced when fuel is burnt and if the chimney is blocked, this can seep into your home instead of being expelled (this gas has to go somewhere). The symptoms of carbon monoxide poisoning include nausea, headache, shortness of breath, and vomiting. Prolonged exposure to this gas can lead to organ failure and even brain damage. Safeguards against carbon monoxide poisoning include special alarms that can detect the presence of this gas in a manner similar to that of the usual smoke alarms.

  3. 3.Toxic Fumes

    Besides carbon monoxide, a variety of other toxic gases are also released into the atmosphere. If the chimney is clogged, there will be no route of escape for these fumes and they can enter inside your house. If members of your family fall ill or show signs of toxic poisoning without any probable cause, you should have your chimney inspected at the earliest.

  4. Signs to Watch Out For

    Falling debris, water streaks, excessive soot, and strong smells form the fireplace are the first indications that your chimney may be clogged. White residue on the inside of the chimney is an indication that too much moisture hassled to mineral salts coming out through the masonry. If you experience a smoky smell inside your house every time you light a fire, this is one strong sign that there may be a blockage in the chimney. This happens because the venting system of the fireplace is not functioning as well as it should be. If the flue liner in your chimney is made of clay or concrete, it is possible that it might have developed cracks over a period of time. These cracks can cause the exhaust gases and even sparks to pass through into the building. Improper installation may be one of the reasons that cracks have developed in the flue.

  5. Fully Qualified

    A professional chimney cleaner or inspector will first examine your fireplace and chimney from all angles and look for any flaws that might have cropped up. Your best bet is to hire someone certified by the Chimney Safety Institute of America (CSIA) ¬since they are well-qualified in evaluating and managing fire hazards, gas leaks, and any other structural damage.

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