Dirty Chimneys – Is Your Fireplace Safe to Use?

The weather is getting colder. In a few more weeks, nighttime temperatures will drop into the upper 40s. We’ll be reaching for warm socks, an extra layer, and blankets as we curl up on the couch to watch our favorite show or enjoy a good book. If you have a fireplace, you have likely already started stocking up on firewood. You can see yourself enjoying the warmth the fire will give off. 

Before you get too cozy in front of that fire, do you know if your fireplace is safe to use?

Three serious concerns

Smoke damage

Dirty or damaged chimneys can fail to operate properly.

The [flue] damper should always be fully open before lighting a fire and when the fireplace is in use. ~ homeguides.sfgate.com

When burning a fire, if using unseasoned or inferior wood, or the temperature of the fire doesn’t remain above 250 degrees, you will get creosote build up. This build up within the chimney can prevent the flue from opening fully. This will let less oxygen in, resulting in a less complete burn.

You will have a less efficient fire – less heat and use more wood. Worse, this increases the amount of creosote and tar buildup in the chimney.

A partially closed damper can also cause smoke to back up into your home. This may not be noticeable immediately. Over time, soot will leave a leave a black film around the fireplace, settle into carpeting, or on furniture.

Health risks

Carbon monoxide poisoning. Carbon monoxide is a by-product of combustion and it kills more than 400 people in the US annual with more than 50,000 treated for accidental poisoning according to the Centers for Disease Control. The less efficient the burn, the more it is produced. If your flue damper doesn’t fully open you are increasing your risk of poisoning. Since it can take several hours of fresh air to rid carbon monoxide from the bloodstream, something most of us do not get when we most use our fireplaces, the effects can build up over a day or two.

Toxic chemicals. Traces of creosote are found in the smoke that rises from open flames. This means if any of that smoke backs up into your home, you could be breathing in those trace amounts, The EPA has stated that coal tar creosote is a probable human carcinogen.


Chimney fires account for 6% of residential home fires according to the National Fire Protection Agency.

Creosote, aside from being toxic to breathe, is highly flammable. As it builds up over time, the accumulation leads to the above issues and increases the likelihood of a fire. When Creosote burns, it does so at an extremely high temperature.  The result can be explosive given the confined space of a chimney and the amount of fuel present.

The biggest danger is that most chimney fires go undetected. They do not get enough oxygen or enough fuel (before there is enough creosote build up) so the burn slow and smolder until they self extinguish.

While the fire itself may have caused no visible damage, the high burn temperatures (up to 2000 degrees) will have damaged the chimney increasing the risk of a more substantial or dangerous fire the next time.

Per NFPA, in the reported 25,000 cases of chimney fires between 2011 and 2015, there was an accompanying loss of 120 million dollars in property damage. Regular cleaning is necessary to prevent these fires. Ideally, the soot residue should not be more than ¼ inch thick.

Creosote isn’t the only danger

Damaged chimneys. Cracked bricks, damaged mortar between the bricks, and damaged liners can impact a chimney’s performance and lead to the risks above. 

Critters and debris. Missing or damaged caps and small gaps can allow debris and critters to get inside the chimney. This can result in the flue being block even when the damper is completely open. While not likely to cause a fire, smoke will back up into the home leading to damage and carbon monoxide poisoning.

Prevent the dangers

Inspect and clean it regularly. The best way to keep yourself safe is to make sure your chimney is inspected and cleaned at least once each year, If you use yours more often or use poor quality wood, we’d recommend having it inspected at least once during the season. 

Even if yours was inspected and cleaned after the final fire last winter, a quick check before you light that first fire of the season is recommended to make sure it is free of debris and critters. 

Use the correct type of wood. This will insure a cleaner, more efficient burn – better for you and your chimney. It may even reduce the number of cleanings needed (though you should not skip the annual inspection). 

The best wood to use is seasoned hardwoods. They burn hotter and cleaner leaving less creosote deposits. 

Avoid wood scraps from construction projects and painted wood as they can give off harmful chemicals.

When was your fireplace last inspected or cleaned?

If you cannot remember or it was more than a year ago, it needs to be inspected.

If it was less than a year ago and you use your fireplace often or use soft, unseasoned firewood, it needs to be inspected.

Your health and safety are at risk if you don’t have your chimney inspected regularly and cleaned as necessary.

Get your chimney inspected and cleaned before you have an issue.

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